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Articles on this Page
- 03/25/16--11:07: _The lives and times...
- 04/04/16--07:34: _Why Protoceratops a...
- 04/29/16--07:55: _The lives and times...
- 05/18/16--08:49: _Quetzalcoatlus: the...
- 06/10/16--03:37: _The dinosaur restin...
- 06/23/16--11:18: _Why the giant azhda...
- 06/29/16--06:26: _New palaeoart book,...
- 07/04/16--02:22: _Recreating an Age o...
- 07/06/16--06:39: _And drepanosaurs mi...
- 07/25/16--12:52: _The 'Pteranodon com...
- 08/12/16--06:38: _Trunk or no trunk, ...
- 08/31/16--00:59: _New paper: at last,...
- 09/12/16--13:04: _A salute to the Ery...
- 10/09/16--06:11: _Exposed teeth in di...
- 10/25/16--14:36: _The markwitton.com ...
- 11/02/16--05:54: _The blog post where...
- 12/20/16--06:17: _The popularity of d...
- 01/18/17--03:50: _New paper: when the...
- 02/17/17--04:02: _Scientists: please ...
- 02/24/17--01:30: _Plesiosaur palaeoar...
- 03/31/17--08:47: _Scientist-palaeoart...
- 04/14/17--05:36: _New paper: pterosau...
- 04/27/17--13:21: _Walking with ichthy...
- 05/31/17--13:18: _Armoured theropod f...
- 06/16/17--02:51: _Revenge of the scal...
- Currie, P. J., & Jacobsen, A. R. (1995). An azhdarchid pterosaur eaten by a velociraptorine theropod. Canadian Journal of Earth Sciences, 32(7), 922-925.
- Hone, D., Tsuihiji, T., Watabe, M., & Tsogtbaatr, K. (2012). Pterosaurs as a food source for small dromaeosaurs. Palaeogeography, Palaeoclimatology, Palaeoecology, 331, 27-30.
- Hwang, K. G., Huh, M., Lockley, M. G., Unwin, D. M., & Wright, J. L. (2002). New pterosaur tracks (Pteraichnidae) from the Late Cretaceous Uhangri Formation, southwestern Korea. Geological Magazine, 139(04), 421-435.
- Kellner, A. W., & Langston Jr, W. (1996). Cranial remains of Quetzalcoatlus (Pterosauria, Azhdarchidae) from Late Cretaceous sediments of Big Bend National Park, Texas. Journal of Vertebrate Paleontology, 16(2), 222-231.
- Kellner, A. W., Rich, T. H., Costa, F. R., Vickers-Rich, P., Kear, B. P., Walters, M., & Kool, L. (2010). New isolated pterodactyloid bones from the Albian Toolebuc Formation (western Queensland, Australia) with comments on the Australian pterosaur fauna. Alcheringa, 34(3), 219-230.
- Lockley, M. G., & Wright, J. L. (2003). Pterosaur swim tracks and other ichnological evidence of behaviour and ecology. Geological Society, London, Special Publications, 217(1), 297-313.
- Rodriguez-de la Rosa, R. A. (2003). Pterosaur tracks from the latest Campanian Cerro del Pueblo Formation of southeastern Coahuila, Mexico. Geological Society, London, Special Publications, 217(1), 275-282.
- Vremir, M., Kellner, A. W., Naish, D., & Dyke, G. J. (2013). A new azhdarchid pterosaur from the Late Cretaceous of the Transylvanian Basin, Romania: implications for azhdarchid diversity and distribution. PLoS One, 8(1), e54268.
- Witton, M. P. (2013). Pterosaurs: natural history, evolution, anatomy. Princeton University Press.
- Witton, M. P., & Naish, D. (2008). A reappraisal of azhdarchid pterosaur functional morphology and paleoecology. PLoS One, 3(5), e2271.
- Witton, M. P., & Naish, D. (2015). Azhdarchid pterosaurs: water-trawling pelican mimics or “terrestrial stalkers”?. Acta Palaeontologica Polonica, 60(3), 651-660.
- Near Eastern griffin culture seems to occur thousands of years before we have evidence for it in central Asia, suggesting Protoceratops anatomy could not be referenced in any way by the original griffin artists.
- Griffin anatomies, in all their variants, are best and entirely explained as chimeras of extant animals. There is no need to invoke any exotic fossil anatomies in their design.
- Griffin iconography, and perhaps written legends, are sufficiently varied to suggest a complex set of origins and legends for these creatures.
- Ancient Greek writings seem to lack compelling references to Protoceratops, and aspects of appearance and behaviour they discuss clearly indicate they were not informed by fossilised animals. Several details of these accounts suggest they must be talking about imaginary creatures.
- Protoceratops fossils are found hundreds of kilometres from ancient Scythian gold mines, undermining the suggestion they might be the source of griffin gold guarding lore. There is no indication that these dinosaur fossils are associated with gold.
- Bowra, C. M. (1956). A Fragment of the Arimaspea. The Classical Quarterly, 6(1/2), 1-10.
- Fastovsky, D. E., Badamgarav, D., Ishimoto, H., Watabe, M., & Weishampel, D. B. (1997). The paleoenvironments of Tugrikin-Shireh (Gobi Desert, Mongolia) and aspects of the taphonomy and paleoecology of Protoceratops (Dinosauria: Ornithishichia). Palaios, 59-70.
- Frankfort, H. (1937). Notes on the Cretan griffin. The Annual of the British School at Athens, 37, 106-122.
- Gane, C. E. (2012). Composite Beings in Neo-Babylonian Art (Doctoral dissertation, University of California, Berkeley).
- Goldfinger, E. (2004). Animal Anatomy for Artists: The Elements of Form: The Elements of Form. Oxford University Press, USA.
- Goldman, B. (1960). The development of the lion-griffin. American Journal of Archaeology, 64(4), 319-328.
- Lambert, O., Godefroit, P., Li, H., Shang, C. Y., & Dong, Z. M. (2001). A new species of Protoceratops (Dinosauria, Neoceratopsia) from the Late Cretaceous of Inner Mongolia (PR China). Bulletin-Institut royal des sciences naturelles de Belgique. Sciences de la Terre, 71, 5-28.
- Mayor, A. (2001). The first fossil hunters: paleontology in Greek and Roman times. Princeton University Press. (First edition)
- Mayor, A. (2011). The first fossil hunters: paleontology in Greek and Roman times. Princeton University Press. (Second edition)
- Mayor, A., & Heaney, M. (1993). Griffins and Arimaspeans. Folklore, 104(1-2), 40-66.
- Phillips, E. D. (1955). The legend of Aristeas: fact and fancy in early Greek notions of East Russia, Siberia, and Inner Asia. Artibus Asiae, 18(2), 161-177.
- Tartaron, T. F. (2014). Cross-Cultural Interaction in the Greek World: Culture Contact Issues and Theories. In Encyclopedia of Global Archaeology (pp. 1804-1821). Springer New York.
- Wyatt, N. (2009). Grasping the Griffin: Identifying and Characterizing the Griffin in Egyptian and West Semitic Tradition. Journal of Ancient Egyptian Interconnections, 1(1), 29-39.
- Frey, E., & Tischlinger, H. (2012). The Late Jurassic pterosaur Rhamphorhynchus, a frequent victim of the ganoid fish Aspidorhynchus?. PloS one, 7(3), e31945.
- Habib, M. & Cunningham, J. 2010. Capacity for Water Launch in Anhanguera and Quetzalcoatlus. Acta Geoscientica Sinica. 31, 24-25
- Habib, M. B., & Ruff, C. B. (2008). The effects of locomotion on the structural characteristics of avian limb bones. Zoological Journal of the Linnean Society, 153(3), 601-624.
- Hazlehurst, G. A., & Rayner, J. M. (1992). Flight characteristics of Triassic and Jurassic Pterosauria: an appraisal based on wing shape. Paleobiology, 18(04), 447-463.
- Hone, D. W., Habib, M. B., & Lamanna, M. C. (2013). An annotated and illustrated catalogue of Solnhofen (Upper Jurassic, Germany) pterosaur specimens at Carnegie Museum of Natural History. Annals of Carnegie Museum, 82(2), 165-191.
- Hone, D. W., & Henderson, D. M. (2014). The posture of floating pterosaurs: Ecological implications for inhabiting marine and freshwater habitats. Palaeogeography, Palaeoclimatology, Palaeoecology, 394, 89-98.
- Hone, D., Henderson, D. M., Therrien, F., & Habib, M. B. (2015). A specimen of Rhamphorhynchus with soft tissue preservation, stomach contents and a putative coprolite. PeerJ, 3, e1191.
- Ősi, A. (2011). Feeding‐related characters in basal pterosaurs: implications for jaw mechanism, dental function and diet. Lethaia, 44(2), 136-152.
- Schweigert, G., Dietl, G. & Wild, R. (2001). Miscellanea aus dem Nusplinger Plattenkalk (Ober-Kimmeridgium, Schwäbische Alb) 3. Ein Speiballen mit Flugsaurierresten. Jahresberichte und Mitteilungen des Oberrheinischen Geologischen Vereines, 83, 357-364
- Weber, F. (2013). Paléoécologie des ptérosaures 3. Les reptiles volants de Solnhofen, Allemagne. Fossiles. 14. 50-59.
- Wellnhofer, P. 1975. Die Rhamphorhynchoidea (Pterosauria) der Oberjura-Plattenkalke Süddeutschlands. Palaeontoographica A, 149, 1-30.
- Witton, M. P. (2008). A new approach to determining pterosaur body mass and its implications for pterosaur flight. Zitteliana, 28, 143-159.
- Witton, M. P. (2015). Were early pterosaurs inept terrestrial locomotors? PeerJ, 3, e1018.
- 05/18/16--08:49: Quetzalcoatlus: the media concept vs. the science
- Andres, B., & Myers, T. S. (2012). Lone star pterosaurs. Earth and Environmental Science Transactions of the Royal Society of Edinburgh, 103(3-4), 383-398.
- Cai, Z., & Wei, F. (1994). On a new pterosaur (Zhejiangopterus linhaiensis gen. et sp. nov.) from Upper Cretaceous in Linhai, Zhejiang, China. Vertebrata Pal Asiatica, 32(3), 181-194.
- Godfrey, S. J. & Currie, P. J. (2005). 16. Pterosaurs Dinosaur Provincial Park: A Spectacular Ancient Ecosystem Revealed, 1, 292.
- Kellner, A. W., & Langston Jr, W. (1996). Cranial remains of Quetzalcoatlus (Pterosauria, Azhdarchidae) from Late Cretaceous sediments of Big Bend National Park, Texas. Journal of Vertebrate Paleontology, 16(2), 222-231.
- Lawson, D. A. (1975a). Could pterosaurs fly?, Science, 188: 676-678
- Lawson, D. A. (1975b). Pterosaur from the Latest Cretaceous of West Texas. Discovery of the Largest Flying Creature. Science, 187: 947-948.
- McGowen, M.R.; Padian, K.; de Sosa, M.A.; Harmon, R.J. (2002). "Description of Montanazhdarcho minor, an azhdarchid pterosaur from the Two Medicine Formation (Campanian) of Montana". PaleoBios 22 (1): 1–9.
- Nessov, L. A. "Giant flying reptiles of the family Azhdarchidae. I. Morphology, systematics." Vestnik Leningradskogo Universiteta, Seriya 7, no. 2 (1991): 14-23.
- Vremir, M., Kellner, A. W., Naish, D., & Dyke, G. J. (2013). A new azhdarchid pterosaur from the Late Cretaceous of the Transylvanian Basin, Romania: implications for azhdarchid diversity and distribution. PLoS One, 8(1), e54268.
- Vremir, M., Witton, M., Naish, D., Dyke, G., Brusatte, S. L., Norell, M., & Totoianu, R. (2015). A Medium-Sized Robust-Necked Azhdarchid Pterosaur (Pterodactyloidea: Azhdarchidae) from the Maastrichtian of Pui (Hateg Basin, Transylvania, Romania). American Museum Novitates, (3827), 1-16.
- Witton, M. P. (2013). Pterosaurs: Natural History, Evolution, Anatomy. Princeton University Press.
- Witton, M. P., & Habib, M. B. (2010). On the size and flight diversity of giant pterosaurs, the use of birds as pterosaur analogues and comments on pterosaur flightlessness. PloS one, 5(11), e13982.
- Witton, M. P., Martill, D. M. and Loveridge, R. F. 2010. Clipping the wings of giant pterosaurs: comments on wingspan estimations and diversity. Acta Geoscientica Sinica, 31 (1), 79-81.
- 06/10/16--03:37: The dinosaur resting pose debate: some thoughts for artists
- Amlaner, C. J., & Ball, N. J. (1983). A synthesis of sleep in wild birds. Behaviour, 87(1), 85-119.
- Bennett, S. C. (2003). New crested specimens of the Late Cretaceous pterosaur Nyctosaurus. Paläontologische Zeitschrift, 77(1), 61-75.
- Fastovsky, D. E., Badamgarav, D., Ishimoto, H., Watabe, M., & Weishampel, D. B. (1997). The paleoenvironments of Tugrikin-Shireh (Gobi Desert, Mongolia) and aspects of the taphonomy and paleoecology of Protoceratops (Dinosauria: Ornithishichia). Palaios, 59-70.
- Gao, C., Morschhauser, E. M., Varricchio, D. J., Liu, J., & Zhao, B. (2012). A second soundly sleeping dragon: new anatomical details of the Chinese troodontid Mei long with implications for phylogeny and taphonomy. PloS one, 7(9), e45203.
- Goldfinger, E. (2004). Animal Anatomy for Artists: The Elements of Form: The Elements of Form. Oxford University Press.
- Klein, N., Christian, A., & Sander, P. M. (2012). Histology shows that elongated neck ribs in sauropod dinosaurs are ossified tendons. Biology letters, rsbl20120778.
- Lockley, M., Matsukawa, M., & Jianjun, L. (2003). Crouching theropods in taxonomic jungles: ichnological and ichnotaxonomic investigations of footprints with metatarsal and ischial impressions. Ichnos, 10(2-4), 169-177.
- Mallison, H. (2010a). The digital Plateosaurus II: an assessment of the range of motion of the limbs and vertebral column and of previous reconstructions using a digital skeletal mount. Acta Palaeontologica Polonica, 55(3), 433-458.
- Mallison, H. (2010). CAD assessment of the posture and range of motion of Kentrosaurus aethiopicus Hennig 1915. Swiss Journal of Geosciences, 103(2), 211-233.
- Milàn, J. (2006). Variations in the morphology of emu (Dromaius novaehollandiae) tracks reflecting differences in walking pattern and substrate consistency: ichnotaxonomic implications. Palaeontology, 49(2), 405-420.
- Organ, C. L. (2006). Biomechanics of ossified tendons in ornithopod dinosaurs. Paleobiology, 32(04), 652-665.
- Organ, C. L., & Adams, J. (2005). The histology of ossified tendon in dinosaurs. Journal of Vertebrate Paleontology, 25(3), 602-613.
- Paul, G. S. (2010). The Princeton field guide to dinosaurs. Princeton University Press.
- Russell, D. A., & Dong, Z. M. (1993). A nearly complete skeleton of a new troodontid dinosaur from the Early Cretaceous of the Ordos Basin, Inner Mongolia, People's Republic of China. Canadian Journal of Earth Sciences, 30(10), 2163-2173.
- Xu, X., & Norell, M. A. (2004). A new troodontid dinosaur from China with avian-like sleeping posture. Nature, 431(7010), 838-841.
- Arambourg, C. (1954). Sur la presence dun pterosaurien gigantesque dans les phosphates de Joradanie. Comptes Rendus Hebdomadaires des Seances de l'Academie des Sciences, 238(1), 133-134.
- Arambourg, C. (1959). Titanopteryx philadelphiae nov. gen., nov. sp., ptérosaurien géant. Notes et Mémoires sur le Moyen-Orient, 7, 229-234.
- Bramwell, C. D., & Whitfield, G. R. (1974). Biomechanics of Pteranodon. Philosophical Transactions of the Royal Society B: Biological Sciences, 267(890), 503-581.
- Buffetaut, E., Grigorescu, D., & Csiki, Z. (2002). A new giant pterosaur with a robust skull from the latest Cretaceous of Romania. Naturwissenschaften, 89(4), 180-184.
- Buffetaut, E., Grigorescu, D., & Csiki, Z. (2003). Giant azhdarchid pterosaurs from the terminal Cretaceous of Transylvania (western Romania). Geological Society, London, Special Publications, 217(1), 91-104.
- Frey, E., & Martill, D. M. (1996). A reappraisal of Arambourgiania (Pterosauria, Pterodactyloidea): One of the world's largest flying animals. Neues Jahrbuch fur Geologie und Palaontologie-Abhandlungen, 199(2), 221-248.
- Langston, W. (1981). Pterosaurs. Scientific American, 244, 122-136.
- Lawson, D. A. (1975). Pterosaur from the Latest Cretaceous of West Texas. Discovery of the Largest Flying Creature. Science, 187: 947-948.
- Martill, D. M., Frey, E., Sadaqah, R. M., & Khoury, H. N. (1998). Discovery of the holotype of the giant pterosaur Titanopteryx philadelphiae ARAUBOURG 1959, and the status of Arambourgiania and Quetzalcoatlus. Neues Jahrbuch fur Geologie und Palaontologie-Abhandlungen, 207(1), 57-76.
- Steel, L., Martill, D.M., Kirk, J., Anders, A., Loveridge, R.F., Frey, E. J.G. Martin (1997). Arambourgiania philadelphiae: giant wings in small halls. The Geological Curator, 6(8): 305-313
- Stein, R. S. (1975). Dynamic analysis of Pteranodon ingens: a reptilian adaptation to flight. Journal of Paleontology, 534-548.
- Taylor, M. P., & Wedel, M. J. (2013). Why sauropods had long necks; and why giraffes have short necks. PeerJ, 1, e36.
- Wellnhofer, P. 1978. Handbuch der Paläoherpetologie. Teil 19: Pterosauria. Gustav Fischer Verlag, Stuttgart. 82 pp.
- Witton, M. P. (2010). Pteranodon and beyond: the history of giant pterosaurs from 1870 onwards. Geological Society, London, Special Publications, 343(1), 313-323.
- 06/29/16--06:26: New palaeoart book, Recreating an Age of Reptiles, out now!
- 07/06/16--06:39: And drepanosaurs might fly... wait, really?
- Berman, D. S., & Reisz, R. R. (1992). Dolabrosaurus aquatilis, a small lepidosauromorph reptile from the Upper Triassic Chinle Formation of north-central New Mexico. Journal of Paleontology, 66(06), 1001-1009.
- Castiello, M., Renesto, S., & Bennett, S. C. (2015). The role of the forelimb in prey capture in the Late Triassic reptile Megalancosaurus (Diapsida, Drepanosauromorpha). Historical Biology, 1-11.
- Colbert, E. H., & Olsen, P. E. (2001). A new and unusual aquatic reptile from the Lockatong Formation of New Jersey (Late Triassic, Newark Supergroup). American Museum Novitates, 1-24.
- Fraser, Nicholas C., and Silvio Renesto. Additional drepanosaur elements from the Triassic fissure infills of Cromhall Quarry, England. Virginia Museum of Natural History, 2005.
- Renesto, S. (2000). Bird-like head on a chameleon body: new specimens of the enigmatic diapsid reptile Megalancosaurus from the Late Triassic of Northern Italy. Rivista Italiana di Paleontologia e Stratigrafia (Research In Paleontology and Stratigraphy), 106(2).
- Renesto, S., & Dalla Vecchia, F. M. (2005). The skull and lower jaw of the holotype of Megalancosaurus preonensis (Diapsida, Drepanosauridae) from the Upper Triassic of Northern Italy. Rivista Italiana di Paleontologia e Stratigrafia (Research In Paleontology and Stratigraphy), 111(2).
- Renesto, S., Spielmann, J. A., Lucas, S. G., & Spagnoli, G. T. (2010). The taxonomy and paleobiology of the Late Triassic (Carnian-Norian: Adamanian-Apachean) drepnosaurs (Diapsida: Archosauromorpha: Drepanosauromorpha): Bulletin 46 (Vol. 46). New Mexico Museum of Natural History and Science.
- Ruben, R. R. (1998). Gliding adaptations in the Triassic archosaur Megalancosaurus. Journal of Vertebrate Paleontology, 18 (3), 73A.
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- Spielmann J. A., Renesto S. and Lucas S. G. (2006). The utility of claw curvature in assessing the arboreality of fossil reptiles.Bulletin of the New Mexico Museum of Natural History and Science 37: 365-368.
- Bennett, S. C. (1992). Sexual dimorphism of Pteranodon and other pterosaurs, with comments on cranial crests. Journal of Vertebrate Paleontology, 12(4), 422-434.
- Bennett, S. C. (1993). The ontogeny of Pteranodon and other pterosaurs. Paleobiology, 19, 92-106.
- Bennett, C. S. (1994). Taxonomy and systematics of the late Cretaceous pterosaur Pteranodon (Pterosauria, Pterodactyloidea). Occasional papers of the Natural History Museum. 169, 1-70
- Bennett, S. C. (2001a). The osteology and functional morphology of the Late Cretaceous pterosaur Pteranodon Part I. General description of osteology. Palaeontographica Abteilung A, 1-112.
- Bennett, S. C. (2001b). The Osteology and Functional Morphology of the Late Cretaceous Pterosaur Pteranodon Part II. Size and Functional Morphology. Palaeontographica Abteilung A, 113-153.
- Carpenter, K. (2008). Vertebrate biostratigraphy of the Smoky Hill Chalk (Niobrara Formation) and the Sharon Springs Member (Pierre Shale). In High-Resolution Approaches in Stratigraphic Paleontology (pp. 421-437). Springer Netherlands.
- Eaton, G. F. (1910). Osteology of Pteranodon. Connecticut Academy of Arts and Sciences, Memoirs.
- Everhart, M. J. (2005). Oceans of Kansas. Indiana University Press.
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- Weissenböck, N. M., Weiss, C. M., Schwammer, H. M., & Kratochvil, H. (2010). Thermal windows on the body surface of African elephants (Loxodonta africana) studied by infrared thermography. Journal of Thermal Biology, 35, 182-188.
- Weissenböck, N. M., Arnold, W., & Ruf, T. (2012). Taking the heat: thermoregulation in Asian elephants under different climatic conditions. Journal of Comparative Physiology B, 182(2), 311-319.
- Wright, P. G., & Luck, C. P. (1984). Do elephants need to sweat?. South African Journal of Zoology, 19(4), 270-274.
- Agnolin, F. L., & Varricchio, D. (2012). Systematic reinterpretation of Piksi barbarulna Varricchio, 2002 from the Two Medicine Formation (Upper Cretaceous) of Western USA (Montana) as a pterosaur rather than a bird. Geodiversitas, 34(4), 883-894.
- Bennett, S. C. (1993). The ontogeny of Pteranodon and other pterosaurs. Paleobiology, 19(01), 92-106.
- Benson, R. B., Frigot, R. A., Goswami, A., Andres, B., & Butler, R. J. (2014). Competition and constraint drove Cope's rule in the evolution of giant flying reptiles. Nature communications, 5, 3567.
- Butler, R. J., Benson, R. B., & Barrett, P. M. (2013). Pterosaur diversity: untangling the influence of sampling biases, Lagerstätten, and genuine biodiversity signals. Palaeogeography, Palaeoclimatology, Palaeoecology, 372, 78-87.
- Godfrey, S. J., & Currie, P. J. (2005). Pterosaurs. Dinosaur Provincial Park: A Spectacular Ancient Ecosystem Revealed, 292-311.
- Hone, D. W. E., & Benton, M. J. (2007). Cope's Rule in the Pterosauria, and differing perceptions of Cope's Rule at different taxonomic levels. Journal of Evolutionary Biology, 20(3), 1164-1170.
- Kellner, A. W. (2015). Comments on Triassic pterosaurs with discussion about ontogeny and description of new taxa. Anais da Academia Brasileira de Ciências, 87(2), 669-689.
- Martin-Silverstone, E., Witton, M. P., Arbour, V. M, & Currie, P. J. (2016). A small azhdarchoid pterosaur from the latest Cretaceous, the age of flying giants. Royal Society Open Access, 3, 160333.
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- Vremir, M., Kellner, A. W., Naish, D., & Dyke, G. J. (2013). A new azhdarchid pterosaur from the Late Cretaceous of the Transylvanian Basin, Romania: implications for azhdarchid diversity and distribution. PLoS One, 8(1), e54268.
- Vremir, M., Witton, M., Naish, D., Dyke, G., Brusatte, S. L., Norell, M., & Totoianu, R. (2015). A Medium-Sized Robust-Necked Azhdarchid Pterosaur (Pterodactyloidea: Azhdarchidae) from the Maastrichtian of Pui (Haţ eg Basin, Transylvania, Romania). American Museum Novitates, (3827), 1-16.
- 09/12/16--13:04: A salute to the Erythrosuchidae
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- 10/25/16--14:36: The markwitton.com H. P. Lovecraft Halloween Special
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- 12/20/16--06:17: The popularity of dinosaurs - for better, for worse
- Ross, R., Duggan-Haas, D. and Allmon, W. (2013). The posture of Tyrannosaurus rex: Why do student views lag behind the science? Journal of Geoscience Education, 61, 145-160
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- 02/17/17--04:02: Scientists: please pay more attention to palaeoart
- The proportions of the subject should be accurate to those indicated by its fossil remains
- The skeleton of the subject should fit within the restored soft-tissue volume
- Depicted poses should conform to predictions of joint motion
- The soft-tissue volume should - at minimum - be informed by predictions of muscle bulk derived from fossil remains as well as relevant data from modern, related species
- Soft-tissues restoration should be informed where possible by fossil data, or else via robust predictive techniques, such as phylogenetic bracketing
- 02/24/17--01:30: Plesiosaur palaeoart: thoughts for artists
- Carpenter, K., Sanders, F., Reed, B., Reed, J., & Larson, P. (2010). Plesiosaur swimming as interpreted from skeletal analysis and experimental results. Transactions of the Kansas Academy of Science, 113(1/2), 1-34.
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- Anything to do with basic measurements, including the size of the subject relative to its environment and other species, or the proportions of its body. Obtaining metrics from 2D art can be difficult if a subject is obliquely posed or foreshortened, but their rough proportions can be estimated based on their relationship to other body parts. If in doubt, it’s better to get the artist to check their work than to ignore it. Pay particular attention to the proportions of the head to the rest of the body, the size of the torso, and the ratios of the limb bones, as these are prone to errors.
- Whether the skeleton of the subject fits within the restored soft-tissue volumes. Especially notice the shape of the head and teeth, the cross-section and length of the torso, and the bulk of the appendages, as these are often problem areas. Also make sure the position of the shoulders is correct – it is often more challenging to reconstruct the pectoral region than the pelvic, so the forelimb attachment region can end up in strange places.
- Whether the chosen pose breaches predictions of joint articulation. Over-stretched limbs, as well as exaggerated neck and tail poses, are key to look at here.
- Whether appropriate fossil soft-tissues have been factored into the painting. This includes tissue types (e.g. correct integument) and aspects of tissue bulk. Where tissue types are unknown, check that the predicted substitute is based on sensible use of phylogenetic bracketing and comparative anatomy.
- Finally, note whether the species depicted in the artwork were actually contemporaneous, and that the restored environments and climates are appropriate.
- 04/14/17--05:36: New paper: pterosaur palaeoecology, as told by the fossil record
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- 04/27/17--13:21: Walking with ichthyosaurs: the amphibious ichthyosaur hypothesis
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- 06/16/17--02:51: Revenge of the scaly Tyrannosaurus
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- Xu, X., Wang, K., Zhang, K., Ma, Q., Xing, L., Sullivan, C., ... & Wang, S. (2012). A gigantic feathered dinosaur from the Lower Cretaceous of China. Nature, 484(7392), 92-95.
Discussions of the lifestyles of fossil animals primarily centre around their functional morphology - the use of comparative anatomy and biomechanical calculations to assess their anatomical suitability to certain habits and behaviours. We use these approaches to deduce their likely diets, locomotory strategies, likely interactions with ancient environments and other organisms, and so on. But despite the widespread and proven utility of these techniques, it's widely regarded that these approaches can only provide probabilities and hypotheses about fossil habits. They allow us to predict, but not necessarily know how ancient animals functioned in their respective ecosystems. For the latter, we rely on fossils to provide us with direct records of animal habits - gut content, evidence of animals attacking and ingesting each other, trace evidence of foraging strategies and so on. For vertebrates, these fossils are very rare - hence our general reliance on functional anatomy - and single examples of palaeoecologically-significant fossils can provide crucial insights into ancient lifestyles and ecosystems.
As you might expect, such fossils are particularly rare for pterosaurs. Flying reptiles were not prone to fossilisation at the best of times and this - through simple probability - dramatically lowers their chance of forming fossils with palaeoecological significance. As recently as the 1990s some authors lamented the lack of these fossils and tried to ascribe some significance to their rarity. But renewed interest in pterosaur science, an increased rate of discovery of flying reptile remains and greater alertness for details on fossil specimens has seen our sample size of palaeoecologically-significant pterosaur specimens grow considerably in the last few years. These records have been augmented more in some taxa than others so that our record of pterosaur palaeoecology is looking increasingly patchy: some groups now now have a half-dozen or more of these fossils to their names, others have none at all. There's probably no real significance to this other than the habits and anatomy of some pterosaurs being more suited to recording these fossils than others.
I thought it might be fun to take a look at two pterosaur taxa with increasingly good palaeoecological records. In an upcoming post, we'll look at the really quite excellent palaeoecological data for the Jurassic pterosaur Rhamphorhynchus muensteri, but today I want to discuss the palaeoecology of azhdarchids. That's right: the lifestyles of these sometimes giant, sometimes long necked, always edentulous, and increasingly famous flying reptiles are not only predicted by functional morphology, but can be deduced somewhat from fossils too. Thanks to a number of specimens discovered in recent decades we have an idea what happened to azhdarchids when they died, what sort of animals they must have encountered in day to day life, and maybe even how they foraged.
Meeting the (teeth of the) neighboursThe majority of the azhdarchid palaeoecological record pertains to specimens showing which animals ate them, their teeth and puncture marks being left on azhdarchid bones, or else azhdarchid remnants being found in the torsos of other animals as gut content. One of the most famous of these fossils is an incomplete azhdarchid skeleton from the upper Cretaceous Dinosaur Park Formation of Canada. This fossil is noteworthy for not only being one of the most substantial pterosaur fossils from Canada, but also for the tooth gouges and embedded dinosaur tooth found at the distal end of the bone (Currie and Jacobsen 1995). The tooth belongs to the 2 m long dromaeosaur Saurornitholestes langstoni, and the size and provenance of the gouges indicate they were probably made by the same species, perhaps the same individual. The size discrepancy between the pterosaur and dinosaur here is pretty dramatic. Check out the size of the tibiotarsus of the (c. 6 m wingspan) pterosaur compared to the embedded tooth:
|Immature azhdarchid humerus from the Dinosaur Park Formation of Alberta, Canada, with an embedded dromaeosaur tooth (arrowed). Note the size of the pterosaur remains compared to those of the dinosaur. Image by Liz Martin-Silverstone, borrowed from her Twitter account.|
|A Velociraptor mongoliensis chest cavity with pterosaur remains, probably belonging to an azhdarchid, as gut content. Black arrows show pterosaur bone, white arrow indicates a pathological rib. Borrowed from Dave Hone's Archosaur Musings.|
|Holotype cervical vertebrae III and IV of Eurazhdarcho langendorfensis, with possible crocodyliform tooth marks outlined and arrowed. From Vremir et al. (2013).|
Azhdarchid bones as an insect hotel?A further possible record of azhdarchid consumption pertains to strange oval punctures at the back of a Quetzalcoatlus sp. skull (Kellner and Langston 1996). These may record tooth marks, although there is no obvious indication as to what animal might have made them. A rather different take on them was suggested by Kellner et al. (2010), who noted that insect borings had been found the same Quetzalcoatlus material. Kellner et al. suggest that these borings were described by Kellner and Langston (1996) but, to my knowledge, this suggestion is an error as I can find no mention of insect borings in the 1996 paper. I assume this comment provides a different interpretation of the skull punctures, but it might not. I'd really like to know more about this, as there are as yet no confirmed cases of pterosaur bones being utilised by insects. I wonder if this is a simple mistake, or might pertain to details of as-yet undescribed portions of Quetzalcoatlus anatomy?
An azhdarchid foraging trace?
Such a beak scrape might be known preserved alongside a possible azhdarchid track from the Late Cretaceous (Campanian) Cerro del Pueblo Formation of North Mexico (Rodriguez-de la Rosa 2003). This track comprises one well-preserved footprint and a series of handprints, alongside several sharp, linear gouges. Other tracks from this locality - known as the El Pelillal tracksite - include turtles, crocodylomorphs, theropods and mammal-like creatures, and the sedimentary setting is considered a shallow, freshwater environment. When described, these pterosaur prints were considered to represent the generic pterodactyloid trace Pteraichnus (Rodriguez-de la Rosa 2003), but the footprint bears little similarity to the broad, triangular-shaped impressions of this ichnotaxon (below). In my 2013 book I argued that the narrow form, pronounced heel impression and short, blunt toes of this print much more reminiscent of Haenamichnus, a trace thought with good reason to represent the footfalls of azhdarchids (below, Hwang et al. 2002; Witton 2013). The age of the specimen is further indication of an azhdarchid identity, the Campanian being a stage of the Mesozoic where azhdarchids seem to largely dominate pterosaur evolution.
What these fossils might indicate about azhdarchid pterosaur palaeobiology
|Azhdarchid terrestrial stalking, the infographic. From Witton and Naish 2015.|
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|Protoceratops, the Late Cretaceous horned dinosaur widely suggested as being the inspiration for the griffin myth. This image shows the lesser seen P. hellenikorhinus, a larger, more ornamented species of Protoceratops than the familiar P. andrewsi.|
|Bird-griffin statue, 7th century BCE. Was Protoceratops the inspiration for this creation? From Mayor and Heaney (1993).|
I recently became genuinely interested in this interpretation as part of research into the earliest accounts of palaeoart - if griffin art is indeed of horned dinosaur origin, it might qualify as some of the oldest on record. But reading about the Protoceratops-griffin hypothesis (in Mayor and Heaney 1993; Mayer 2011) did not deliver the proverbial 'nugget of truth' behind the griffin myth I expected based on its fame. My impression was that evidence cited for this hypothesis was generalised to account for as much griffin lore as possible, that several major, obvious questions remained unanswered, and that there was not any attempt to refute other, non-fossiliferous takes on griffin origins. Digging into the primary literature on griffin iconography seemed to confirm my concerns, suggesting that the Protoceratops-griffin hypothesis is unfavourable among archaeologists (e.g. Frankfort 1937; Goldman 1960; Wyatt 2009; Tartaron 2014). Moreover, there are far more parsimonious and well substantiated takes on these creatures which do not rely on fossil data. In the interests of providing a counter-argument to all the 'pro'-Protoceratops-griffin hypothesis media out there, I'm sharing the products of my research here.
The griffin timelinePerhaps the largest issue with the Protoceratops-griffin hypothesis is the fact it largely ignores griffin lore before the 7th century BCE. Griffin iconography extends deep into human history with one of their best early appearances dating to 4th millennium BCE Susa - an ancient city in what is now Iran (below, Frankfort 1937). Similarly aged or older artefacts from Egypt also show griffin-like forms (Wyatt 2009), and by the 3rd millennium BCE griffins were a regular component of art in many Near Eastern countries. The role of griffins in these communities remains a matter of controversy because we have little or no written explanation of their significance. Nevertheless, they are abundant enough to suggest some importance in these cultures, and modern scholars have attempted to interpret griffin imagery based on religious and cultural practises of these times (e.g. Wyatt 2009).
|Line drawing of perhaps the oldest known image of a griffin, from Susa, 4th millennium BCE. From Frankfort (1937).|
Taking this point further, overlooking the early history of griffin art also means that the Protoceratops-griffin hypothesis does not engage with current, mainstream interpretations of the spread of griffin culture to Ancient Greece. Griffins are thought to have become popular in Greece during the 'Orientalizing Period', a cultural event occurring around the 7th century BCE when Greek art, technology and literature became heavily influenced by Near Eastern civilizations (Tartaron 2014). Put simply, the uptake of griffins into Greek culture coincides exactly with their sudden interest in the guys who'd been drawing and sculpting griffins for thousands of years. It's easy to understand why this is the preferred explanation for the rise of Grecian interest in griffin imagery. It involves the civilisations known to have depicted these animals before anyone else, fits the dates attributed to Greek and Near Eastern griffin art perfectly, and is easily explained as part of a well-established period of cultural exchange between these peoples. A compelling explanation is needed here to explain why this interpretation is inferior to the far more complex one involving distant peoples, a disjointed chronology and fossil animals found 6000 miles away to the East.
Griffin appearance, variation and the 'need' for exotic fossil anatomyThe Protoceratops-griffin hypothesis also presents a simplified interpretation of griffin iconography. Numerous variants on griffins are found in the ancient world, reflecting differences in anatomy, pose and behaviour. The 'bird-griffin' - the winged lion with an avian head (see images, above and below)- is the type Protoceratops is thought to have inspired, but is just one of many griffin chimeras identified by researchers. Reflecting taxonomy on real animals, the identification of distinctive griffin 'species' varies between researchers, but they are generally thought to include wingless sphinxes (human head on a recumbent lion), bipedally standing winged lions with human heads, winged humans with avian heads, winged lions, long necked 'lion-griffins' (sometimes called 'lion-dragons'), and lions with avian heads, wings and forelimbs (Frankfort 1937; Goldman 1960; Wyatt 2009; Gane 2012). Within these forms are more variation: they may or may not include wings, tails, ears, 'crests' or horns on the snout, manes of hair or feathers, and teeth, as well as differences in neck length, mouth gape and claw size. The animal species used in these chimeras differ too. For instance, there are bird-griffins with eagle, peacock and falcon heads, a variety of big cat species are thought to be used for the body and limbs. Tails may be of either avian or felid identity.
|A selection of griffins forms from Goldman (1960). Note variation in tails, faces, neck length and ears.|
However, this homogeneous treatment of griffin imagery is troublesome, for two reasons. Firstly, the disregarding of griffin form shows a somewhat selective approach to evidence gathering, highlighting elements that suit the Protoceratops origin while ignoring those which are problematic. The fact is most griffin artworks do not look like Protoceratops beyond the superficial similarity of being being beaked quadrupeds (see below). Furthermore, griffin art remains differentiated even after Greek and Scythian cultures were known to have been communicative and, in theory, tales of Protoceratops could influence griffin depictions. This homogenising of griffin forms also contradicts modern interpretations of griffin art. Many researchers stress the unique histories, origins and cultural significance of different griffin forms, some authors even directly cautioning about treating these chimeras as interchangeable for fear of obscuring their true meaning and history (e.g. Goldman 1960; Wyatt 2009; Gane 2012). Most scholars simply see griffins as chimeras - creatures invented from components of animals and human individuals for symbolic or literary intent (Wyatt 2009; Gane 2012). As with other chimeras, the difference between griffin types likely reflects efforts to convey information about these creatures or the scenarios they're depicted in. For example, the addition of wings may indicate swiftness or divinity; large, erect ears suggest alertness; claws suggest ferocity and so on. These features were not added randomly to griffin art, and the development of distinctive griffin types can be traced over time (e.g. Goldman 1960). The message from mainstream archaeology seems to be that griffin iconography had complex origins and development within the framework of chimera creation common to ancient cultures, and that generalising their form is probably not the best way to understand them.
|Sketch of a juvenile Protoceratops andrewsi skull, right lateral view.|
It should be stressed that much of this contrasts with the anatomy of Protoceratops. I need to be careful that I don't set up a straw man here - after all, it's likely we know far more about Protoceratops than anyone who lived thousands of years ago, and the hypothetical passing of tales about Protoceratops from central Asia to eastern Europe is an incredibly long game of Chinese whispers. However, if the Protoceratops-griffin hypothesis is to be accepted it needs to pass some basic anatomical tests, even if they are very simple. Let's start with the head. Immediately obvious is that there is nothing projecting rearwards from the posterior head region of most griffins, whereas all Protoceratops (even very small juveniles) have some sort of frill extending posterodorsally from the back of the skull (above). The ears and crests of griffins, explained as being the broken frills of Protoceratops fossils, are structures which project upwards from the head, not backwards. If we must give these structures a basis in reality, we can look to the ornamental head feathers of birds for the crests (remember that the heads of some elaborate birds, like peacocks, are used in some griffin art) and any number of common mammal species for the ears. These are surely simpler alternatives than the broken skull bones of dinosaur fossils occurring thousands of miles away. It is often suggested that griffin wings might be mistaken interpretations of the Protoceratops frill, but the wings are clearly set on the shoulders in most reconstructions and behind lion-like neck manes in some imagery. Moreover, as noted above, not all griffins have wings. Protoceratops is also not toothless, its densely packed cheek teeth being obvious in even weathered skulls. The majority of griffin images show a fully toothless beak far more like that of a bird than a ceratopsian dinosaur.
|Scott Hartmans's skeletal reconstruction of Protoceratops andrewsi. Borrowed from the excellent Scott Hartman's Skeletal Drawing.com.|
Written accounts of griffin behaviour, and the development of griffin loreEven if Protoceratops did not inform the raw appearance of griffins, could it be referenced in written accounts of griffin appearance and behaviour, such as their desert-living, parental care and gold-guarding habits? It's perhaps these accounts which provide the best evidence for the Protoceratops-griffin hypothesis, as it's these which indicate the deserts of central Asia as the griffin's home and their association with gold. It's worth summarising some details of the first griffin accounts here as their nature and propagation is important. Please check out Phillips (1955), Bowra (1956), Mayor and Heaney (1993) and Mayor (2011) for more details.
Much of Greek griffin lore is derived from stories of the Greek poet Aristeas, who travelled through Asia in c. 675 BCE. His adventures and travels are first recorded in texts from 460-450 BCE (Mayor and Heaney 1993) and were so influential that they continued to be referenced well into the Common Era. However, it's worth stressing that these stories are semi-mythical tales of a semi-mythical man: Aristeas was a real chap, but he is described as seeing and doing things which are combinations of real and fantastic phenomena. Scholars still discuss the realities behind the locations, events, creatures, and peoples Aristeas encountered, and even ancient Greek authors, such as Herodotus, did not believe everything Aristeas was said to have seen and done (Phillips 1955, Bowra 1956). Among the earliest accounts of Aristeas' travels is the tragedy Prometheus Bound, a tale involving gods, titans, gorgons and other monsters. Here, griffins and other creatures were suggested to live to the far north-east of Greece in a desolate desert setting where nomadic barbarians (the Scythians) also hunted for gold. Other documents from the fifth century BCE, also influenced by tales of Aristeas, tell of griffins guarding the gold sought by men and other beasts. Griffin burrows were mentioned by Pliny the Elder's Naturalis Historia, written in 77 CE, as well as by Pausanias in 170 CE. These authors, again citing Aristeas, described how griffins were engaged in a constant war with a race of one-eyed men, the Arimaspi (Bowra 1956). Later accounts, penned in 200 CE, provide specifics of griffin anatomy and behaviour. They include the familiar accounts of their far eastern habitation of mountains and deserts, as well as new information: their membranous wings (considered useless for flight), the extent of their feathering, the colouration of different body parts, the fiery look in their eyes, the fact that men cannot best adult individuals but can capture their offspring, their nesting behaviour and parental nature, and how miners prospect for gold at night to avoid upsetting them.
This also present a further complication to the Protoceratops-griffin hypothesis: are Protoceratops localities likely to contain gold when they're so far away from the alluvial gold sites? Both Mayor and Heaney (1993) and Mayor (2011) argue that desert storms may have transported nuggets of gold to Protoceratops localities, and that seeing these transported nuggets alongside Protoceratops fossils may account for the gold-guarding element of the griffin mythos. This is something we can test because the geology of Protoceratops sites is well documented and understood. Assuming the same basic meteorological processes occur today as thousands of years ago, we should see evidence of windswept gold in the Protoceratops bonebeds. But as far as I'm aware, no gold has been reported from these sites, either as surface debris or as buried elements. Moreover, although the possibility of wind transportation is not excluded entirely, no gold is mentioned by the palaeontologists with Mongolian field experience interviewed by Mayor and Heaney (1993) or Mayor (2011). All this considered, the evidence for it seems the link between Protoceratops and gold deposits is not as strong as it first seems.
Finally, it's worth noting that the Greek accounts of griffins may no longer be the only texts on these creatures from the first century BCE. Gane (2012) discusses Babylonian and Neo-Assyrian literature which is tentatively thought to describe another take on griffin lore. They provide a very different interpretation of griffins, where they are divine guardians against evil spirits and possibly associated with funerary rites. This sounds little like the idea that they were desert-dwelling, gold-hoarding wild animals, and of course suggests no obvious link to fossil animals of China and Mongolia. The implication here is that the Greek stories are only one set of lore about griffins. They are more familiar to us because of their transition to the post-classical period, but they might not be the only, or even the original interpretation of these creatures. Thus, even if Protoceratops is something to do with the griffin - which is far from clear - it is likely only involved in one component of griffin folklore. This seems to echo points made above about the griffin is a very old and complex concept, and how interpretations of its origins are blurred by multiculturalism.
So... is Protoceratops the basis of the griffin myth?Before we answer that, here's a quick summary of the main issues outlined here:
This Protoceratops article and painting has origins at PatreonThe artwork and words you see here are supported by folks who back me on Patreon, the service which allows you to directly support artists and authors with monthly payments. This long, detailed article is exactly the sort of thing I can produce because of this support. If you enjoyed it and would like to see more, you can back my blog from $1 a month. In exchange, you get access to bonus art, discussion and rewards - the more you pledge, you more bonuses you receive! For this post, my patrons were privy to in-progress versions of the painting at the top of the article, discussions of Protoceratops anatomy, and narrowly avoided lots of swearing about rendering of complicated frill geometry. As usual, thanks to everyone who already supports me!
*We see these restored for numerous long tailed pterosaurs, but only Rhamphorhynchus is known, for fact, to have this 'classic' tail vane morphology.
Snap my fish upWhat did Rhamphorhynchus eat? At least three specimens suggest that it foraged for fish of various sizes. The most famous example of such a fossil is sometimes referred to as the 'greedy guts Rhamphorhynchus', an animal which swallowed a fish almost as long as its own torso. This specimen represents a smallish individual, first described by Wellnhofer (1975), with a partly articulated, partly digested fish fossil preserved inside the posterior 60% of the rib cage (below). The orientation of the fish tail fin suggests the fish was swallowed head first, and we have to assume that some major distension of the throat occurred when doing so. That pterosaurs were capable of doing this isn't that surprising considering that extant pterosaur relatives - crocodylians and birds - have mobile throats which aid swallowing of big food items. The relative proportions of these gut contents suggests this animal must've bolted its food like these modern archosaurs, a behaviour rare among mammals but known to occur in at least one large, yellow, bipedal primate. This specimen also presents several elongate elements which defy easy explanation: they're suggested as other food items or even bits of preserved gut tissue by various authors (dark grey in the line drawing below).
|The fossil, interpretive drawing, and restored reality of Jurassic table manners. Disgraceful. |
Line drawing after Wellnhofer (1975).
The one, the only, pterosaur coproliteOf the many questions that keep pterosaur experts up at night - what are they related to? how did they work as functional organisms? how are they related to each other? - none has been greater than what their poop was like. Expelled waste is a common form of fossils in some localities, but remained entirely elusive for flying reptiles until last year when Dave Hone and colleagues (2015) identified the first pterosaur coprolite dropping out of a complete Rhamphorhynchus specimen. Finally, pterosaur workers can sleep easy.
|Rhamphorhynchus muensteri specimen with coprolite (cp). From Hone et al. (2015).|
Fossilised food chainsSeveral Rhamphorhynchus specimens reveal it was prey to other Jurassic animals. Among the least commonly discussed is a small pellet produced by something like a fish or crocodylomorph which contains several Rhamphorhynchus wing bones (Schweigert et al. 2001). This is a rare example of Rhamphorhynchus from the Nusplingen Limestone, a unit lithologically similar to Solnhofen but slightly older. As is so often the case with such fossils, the identity of the pellet maker remains elusive. My own suspicions are of a piscine origin, as modern crocodylians don't tend to spit out bones (they digest them, only regurgitating hair, feathers and other keratinous tissues that are difficult to break down). That may not have been true for fossil crocs, of course.
|Rhamphorhynchus vs. Aspidorhynchus. I guess we should call this one a draw? From Frey and Tischlinger (2012).|
Among the most remarkable Rhamphorhynchus fossils are five instances where it is preserved alongside the predatory fish Aspidorhynchus acutirostris, a long-bodied species that is often much larger than its Rhamphorhynhus prey (Frey and Tischlinger 2012; Weber 2013). These fossils are palaeoecologically notable for three reasons. Firstly, large Solnhofen vertebrates are hardly ever associated, and yet we have five instances of this same pterosaur and fish species being found in touching, or near touching, proximity. Secondly, all five are exquisitely preserved - one example includes a 'mummified' pterosaur with wing membranes, and all are completely articulated. Thirdly, the Rhamphorhynchus are invariably positioned around the skull of the fish, as if a specific, repeated behaviour saw these animals preserved together. These particulars make chance association of these animals unlikely and imply Aspidorhynchus sought out Rhamphorhynchus as food, probably hunting live specimens rather than scavenging floating corpses (as indicated by the excellent preservation of the individual pterosaurs). Frey and Tischlinger (2012) provide a plausible scenario for the deaths of these animals: they reason the Aspidorhynchus tackled prey that became entangled in their jaws before accidentally entering the toxic bottom waters of the Solnhofen waterways. In these anoxic depths the tangled pair would die pretty quickly (if the pterosaur wasn't already dead, of course), leaving us with perfectly preserved bungled predatory acts. The icing on the cake of these specimens is that one of these Rhamphorhynchus specimens has already been mentioned here - that individual with a fish in its throat (Frey and Tischlinger 2012). In this specimen at least, we can assume the pterosaur ate a fish shortly before being attacked itself: a rare instance of a fossil food chain.
The bigger picture of Rhamphorhynchus palaeoecologyCollectively, we have 10 specimens of Rhamphorhynchus telling us something about its position in Mesozoic food webs. That's not bad going for a pterosaur, a famously rare type of fossil, and is actually a pretty good palaeoecological record for any fossil vertebrate. 10 specimens is not enough to tell us everything about the lifestyle of a fossil animal, but does allow us to paint a general picture. They show us that Rhamphorhynchus was adapted to foraging on pelagic prey - often small, probably live fish - and that it must have spent a good amount of time in or around water, as it was clearly an attractant to aquatic predators. These specimens gel neatly with general models of Rhamphorhynchus lifestyle interpreted from their functional anatomy. It's generally thought that Rhamphorhynchus was adapted for life along shorelines - basically a Mesozoic gull. It's not uncommon to be suspicious of such claims nowadays, it being realised that the 'Mesozoic seabird equivalent' almost became a trope, or at least a tremendous over-generalisation, of pre-21st century pterosaur science. But in this case, a gull-like lifestyle is a cogent hypothesis based on studies of wing shape, flight style, tooth and jaw apparatus, and limb function (e.g. Wellnhofer 1975; Hazlehurst and Rayner 1992; Witton 2008, 2015; Ösi 2011). Perhaps research on Rhamphorhynchus was involved in creating the stereotype of pterosaurs as Mesozoic seabirds, but we should not regard it as a victims of this stereotyping itself.
But we should ask ourselves why Rhamphorhynchus palaeoecology is comparably well-represented in the fossil record. It might be something as simple as preservational conditions, but there are plenty of pterosaur Lagerstätten, some of them containing close relatives of Rhamphorhynchus in reasonable abundance, which provide no information about dietary preferences or interactions with predatory species. Is there something intrinsic to Rhamphorhynchus which makes it special? I find several reasons to wonder if Rhamphorhynchus was an atypically aquatic species, not only flying and feeding above water but actually routinely entering it. Firstly, Rhamphorhynchus has a hatchet-shaped deltopectoral crest (the process on the humerus which anchors the flight muscles), a small (or at least narrow) torso and short legs: these are features which Habib and Cunningham (2010) link to routine and efficient aquatic takeoff. Secondly, tests of pterosaur swimming suggest that Rhamphorhynchus had a pretty stable floating posture - not something that can be said for all pterosaurs (Hone and Henderson 2014). Thirdly, it also has comparably large but delicately constructed feet, which might suit paddling, as well as a slender set of forelimb bones (Witton 2015) which recall the streamlined arm bones of swimming and diving birds (Habib and Ruff 2008). Prolonged bouts of swimming might also account for its general abundance, excellent preservation and all-round good fossil record: being immersed in water puts it a step closer to being preserved than other, less aquatic species. Who knows: perhaps it even dived into Solnhofen's toxic bottom waters on occasion, explaining why so many specimens are excellently preserved? Hmmm.... perhaps this warrants further investigation.
Coming soon: could dinosaurs - gasp - lie down on their sides? My take on the greatest of palaeoart debates.
Rhamphorhynchus is supported by fish; this blog is supported by PatreonThe paintings and words featured here are sponsored by the finest human beings on the planet, those folks who support me at Patreon. Backing my blog for as little as $1 a month helps me churn out researched and detailed articles and paintings to accompany them, and in return you get access to bonus blog content: additional commentary, in-progress views and high-resolution artwork, and even free prints. Accompanying this post, we're going to look at the bigger picture of pterosaur palaeoecology: azhdarchids and Rhamphorhynchus are just two lineages with palaeoecological records - what about the rest of Pterosauria? Sign up to Patreon to join that discussion!
|Background: Javelina Formation forest. Mid-ground: the 4.6 m wingspan, super-famous azhdarchid pterosaur Quetzalcoatlus sp. Foreground: lunch.|
As a consultant, the pterosaur I get asked about more than any other is the azhdarchidQuetzalcoatlus. In recent weeks I've been speaking to two completely independent media producers about this animal, and I think just about all my prior TV and film work has involved it somehow, even if not prominently. I suppose Quetzalcoatlus is so popular because it's not just the most famous azhdarchid pterosaur - which are now more popular than ever - but the first animal most people think of as the biggest ever flying creature.
All the pictures, museum exhibitions, sculptures and animations of Quetzalcoatlus suggest it must be a well-understood animal, but it's actually very difficult to provide consultancy on, for several related issues. The first is that the science on the animal itself is unfinished, largely unpublished, and the existing body of work is decades old. The second is that our general understanding of azhdarchid pterosaurs has moved on considerably in the last two decades, and largely without a good grounding of what Quetzalcoatlus actually is. The third, and final, issue is that most parties think Quetzalcoatlus is better understood than it really is, to the point where whole media projects are locked in around it, and consultants are asked to make calls that have little scientific backing. That third point is an important one: 'Quetzalcoatlus the media concept' is a very different beast to 'Quetzalcoatlus the scientific entity'. This can create difficulties when creating programmes, games or artwork of this animal, as the expectations for what can be achieved with Quetzalcoatlus are often beyond what scientists can provide.
In the interests of helping out those who want to use Quetzalcoatlus in their projects, I thought it might be useful to show how 'common knowledge' about Quetzalcoatlus differs from its actual, objective status within 21st century pterosaur science. An important caveat before we go further is that scientific work on Quetzalcoatus is ongoing. A full description and functional assessment is rumoured to be in the works (as, er, it has been for 40 years...) and this will change the way we view this animal tremendously. It can't not do this: the data available on this animal are minimal, so publication of any new details will augment the current situation. In all likelihood this post will be moot, at least in part, when this document is finally published. This piece is being written in May 2016, so please bear in mind that things might have changed if you're reading this at a later date.
The concept.Quetzalcoatlus is a giant azhdarchid pterosaur from Texas, known from substantial remains.
The science.The popular view of Quetzalcoatlus is really a conflation of two taxonomic entities, Quetzalcoatlus northropi and Quetzalcoatlus sp. Both occur in the Late Cretaceous (Maastrichtian) Javelina Formation of southern Texas*. Q. northropi is currently the only 'officially' named species of Quetzalcoatlus, and is the reason we think this animal was so huge. It's also only known from bits and pieces of a gigantic left wing and cannot be regarded as a well known animal. Do not, if you're a TV producer or whatever, expect to film a room full of real fossils for this thing - any skeleton you see of a giant Quetzalcoatlus is almost entirely reconstruction - still impressive, but nearly all calculation and extrapolation.
*It's worth mentioning that Quetzalcoatlus has been identified outside of Texas, scraps of azhdarchid bones from both North America and Europe being allied to this genus. I suspect that most of these should not be referred to Quetzalcoatlus proper, as they're fairly 'generic' azhdarchid bones and, moreover, we have no criteria for what constitutes Quetzalcoatlus within Azhdarchidae itself (see below). I don't want to discuss these now, however, and only mention them for the sake of completeness.
Q. sp., by contrast, is much better represented. Several incomplete skeletons are known (an example can be seen below) that collectively give a near complete picture of Q. sp. osteology. Its this material that gives us our familiar image of Quetzalcoatlus:the long neck, the oversize pointy face, the long limbs and so on. Almost all discussions about the detailed anatomy of Quetzalcoatlus pertain to this material, not the giant wing. The Q. sp. fossils are also a key source of the proportional data used in calculating the 10 m wingspan for the giant Q. northropi animal, even though Q. sp. is much smaller - the complete wing metrics of one specimen give a wingspan of 4.6 m (Unwin et al. 2000).
|Q. sp. partial skeleton figured by Kellner and Langston (1996).|
How the two Quetzalcoatlus species are related to each other, and other azhdarchids, remains critically unexplored and uncertain. It is no exaggeration to say that taxonomic considerations of this important, well-known genus comprise no more than a few sentences in the entirety of technical pterosaur literature. The name Q. northropi was not even erected in a descriptive paper, but as an aside in a brief comment on the likely wingspan of the giant wing specimen (Lawson 1975a). This gave us the northropi name and designated a type specimen (the big wing), and suggested that the smaller specimens were just diminutive, presumably immature versions of the giant species. However, other elements key to species creation - diagnoses, specimen inventories, supporting description or illustrations were not provided, the best alternative being a very short 1975 science paper (Lawson 1975b). Nessov (1991) provided an attempt to diagnose the genus (along with other azhdarchids) but his characters are not useful. Later, Kellner and Langston (1996) suggested that the smaller Quetzalcoatlus skeletons were not juveniles of the giant species, but a distinct species that would be named at a later date. It was this paper that created the 'Q. sp.' moniker, a place-holder for a name we'll perhaps see published in time. Alas, Q. sp. was also created using drive-by taxonomy without justification for separating sp. from northropi, or providing characters to unite these species in a distinct genus among other azhdarchids.
This might all sound like tedious detail irrelevant to reconstructions, media portrayals etc., but the upshot is that the pterosaur community is still largely in the dark about Quetzalcoatlus. We can't really comment on what makes it unique, whether all these bones from Texas should be considered one or two species, how accurate it is to scale up the smaller Quetzalcoatlus to the size of the big wing and so on: that information has been made public yet. Some specific folks might be able to provide those details, but they are not peer-reviewed 'common knowledge'. Therefore, most researchers (including myself) can only talk about Quetzalcoatlus in terms of the few details that have been published, and fill the rest in with 'generic' details of azhdarchid pterosaur palaeobiology.
The concept. Quetzalcoatlus was like all azhdarchids: a long-necked, long-skulled creature with long limbs.
The science. As alluded to above, we have a basic idea of Quetzalcoatlus sp. appearance, even if the vast majority of it remains unpublished. The core aspects of this animal can be built from data titbits gleaned from different papers: a good description of the skulls and mandibles was provided by Kellner and Langston (1996); Witton and Naish (2008) and Steel et al. (1997) gave some details of the cervical vertebrae, and Unwin et al. (2000) provided measurements for nearly all major limb bones. From this, we can be confident that Quetzalcoatlus sp. is the long-necked, long-faced, toothless, short-winged and gracile-limbed creature we have traditionally associated with the Quetzalcoatlus name. I've attempted a skeletal reconstruction of this 4.6 m wingspan species below using these data: some of the bone anatomy is 'generic azhdarchid', but the basic proportions, skull and anterior neck vertebrae should be OK. This skeletal is the basis for the painting at the top of the post.
|Quetzalcoatlus sp. skeletal, using data from Kellner and Langston (1996); Witton and Naish (2008), several other sources of azhdarchid neck data, and Unwin et al. (2000). Yes, it was that long-necked and long-legged.|
A question I have much more trouble answering is what Q. northropi looked like. When we see a giant long-necked Quetzalcoatlus in TV shows or comics, we're seeing a hybrid of the two Quetzalcoatlus animals - the anatomy of sp. crossed with the size of northropi. This approach is not without merit: it's consistent with the existing taxonomy of this animal (such that it is), and other pterosaur fossils confirm that some giant azhdarchids were long-necked, perhaps Q. sp-like creatures.
On the other hand, we only have an incomplete northropi wing skeleton to work from. It's widely recognised that pterosaur wings are among the more conservative aspects of their anatomies - great for identifying pterosaurs to specific groups (we have characterised azhdarchid wings, for instance) but above a basic level of taxonomy they don't tell us much about life appearance. It wasn't always this way. When Quetzalcoatlus was found in the 1970s the smaller Q. sp. skeletons provided our only comprehensive insight into azhdarchid anatomy, and thereafter we assumed that Q. sp. typifies the group. However, azhdarchid pterosaur science has progressed considerably in the last two decades and the group can no longer be considered anatomically uniform. Their skulls can be short and broad, long and narrow, and have deep or slender lateral profiles (Witton 2013). They can have cranial crests (Kellner and Langston 1996), but they might not (Cai and Wei 1994). Their necks can be extremely long, or of more typical pterodactyloid lengths (Vremir et al. 2015). Some had stilt-like limb bones, but others had short forelimb anatomy (McGowan et al. 2001). Such variation seems present in the giants as much as their smaller cousins. I don't think we know what an 'average' azhdarchid looked like yet, but Q. sp. should be viewed as representing only one, relatively exaggerated take on azhdarchid anatomy. It historically seemed safe to make Q. sp. a giant version of this form, but that cannot be regarded as the only option today. For all we know, Q. northropi could be a short-armed, short-necked species with a truncated, deep jaw - quite the opposite of Q. sp..
**I'm expecting people to wonder if Quetzalcoatlus taxonomy has been looked at in detail via cladistic methods. The most complete published assessments I'm aware of are those by Brian Andres (e.g. Andres and Myers 2013) which use seven azhdarchid OTUs, including the two Quetzalcoatlus taxa. The results of such studies remain ambiguous about the affinities of Quetzalcoatlus (Q. sp. and northropi form a polytomy with Arambourgiania). I'd like to see an analysis with more azhdarchid taxa, including some of the more unusual types such as Hatzegopteryx and Montanazhdarcho.
I don't have any real answers or insight on these points. Rather, I'm getting at the fact that our 21st century understanding of azhdarchids and other flying reptiles is becoming complicated, and with our current, superficial insights into what Quetzalcoatlus is and how it's related to other azhdarchids, there may not be one 'right' way to restore northropi. We might be correct to represent it as a giant Q. sp., as per tradition, but we might not.
The concept. Quetzalcoatlus was the biggest animal to have ever flown, even larger than other giant azhdarchids
The science.As with modelling the size of most giant extinct animals, it's difficult to say what giant azhdarchid was the biggest. Q. northropi was certainly up there, recent estimates of its wingspan being in the region of 10 m and predicted body masses of 200-260 kg. But other giant pterosaurs are predicted to be about the same size (see Witton and Habib 2010 for a recent discussion)... and that's about all we can really say. Every giant azhdarchid is represented by scrappy material, so the error bars on any size estimate are large and the calculations themselves are highly sensitive. We would be foolish to use them as anything other than ballpark figures. We can say that Q. northropi was one of the biggest flying animals of all time and, along with other giant azhdarchids, it dwarfed other flying species including most pterosaurs, and all birds and bats. I appreciate some folks will find this lack of clarity frustrating, but that's just how it is: we can't say any more until we understand all the giants - not only Quetzalcoatlus - in more detail.
The concept. The outstanding flight capabilities of giant azhdarchids allowed Quetzalcoatlus to be a continent-hopping animal that occurred in Europe as well as the USA, although the European bones were given a different name: Hatzegopteryx. Some chap called 'Witton' suggested this.
The science.Thanks, I think, to Wikipedia, I've been confronted several times about suggesting the Romanian giant azhdarchid Hatzegopteryx thambema should be synonymised with Quetzalcoatlus. I feel a bit misquoted on this. Yes, I (and colleagues) mentioned this as a qualified possibility in a 2010 abstract and conference talk (Witton et al. 2010), but as part of a broader, detailed discussion about the need to tighten up giant azhdarchid taxonomy. Specifically, we discussed the three named giant azhdarchids - Arambourgianiaphiladelphae, Quetzalcoatlus northropi, and Hatzegopteryxthambema - and stressed issues with their current taxonomy. These issues - hitting some points already tackled here - included the lack of a description and diagnosis for Quetzalcoatlus; the uncertainty over the relationships between Q. northropi and Q. sp.; the scrappy nature and general incomparability of giant azhdarchid fossil remains; their representation by anatomies generally considered unnameable by pterosaur workers, and the identification of several alleged autapomorphies of giant species in other azhdarchid remains.
So... how can Quetzalcoatlus be used in art, film, games etc.?
The take-home here, then, is that Quetzalcoatlus might be the 'best known' giant azhdarchid and the one that everyone wants to feature in their TV shows, films and games, but be forewarned that the scientific status of this animal is rather different to what popular depictions suggest. Moreover, there are alternatives which might be (at time of writing) better understood and just as interesting. If you're planning a TV show, video game or artwork of a giant azhdarchid, remember that there are choices other than the obvious.
This post on the soul-crushing reality of giant pterosaurs is sponsored by Patreon
|Three Sinornithoides youngi, one standing, one sitting, one sunbathing. But would these animals really have adopted resting poses like those of modern birds, as shown here, or would they have relaxed in completely different postures?|
A necessary caveatAsking general questions about how extinct dinosaurs did anything is increasingly difficult to answer in a succinct, concise manner. Dinosauria is an enormous group of animals with huge diversity in body size, gait, proportions, soft-tissue anatomies and so on. These are all things which impact the way an animal might sit or lie down, and in all likelihood there is no one answer to this inquiry. What works for a troodontid may not work for an ankylosaurid, and what works for these may not apply to a sauropod. While there's some merit to taking a general approach to this discussion (and that's what we'll be doing here), this point is something to bear in mind as we go through. The actual answer to this question will be multifaceted, and found through dedicated study of specific dinosaur groups.
What the fossil record tells usCrouching dinosaur traces attributed to bipedal theropods and ornithopods are known from the track record (e.g. Lockley et al. 2003; Milner et al. 2009 and references therein), and these are often used as evidence for dinosaurs generally adopting bird-like, crouched resting postures. Such impressions cannot be regarded as common, but are easily identified by the elongate footprint impressions where the long metatarsal bones and ankle are impressed into the ground behind the toe prints. That at least some of these crouching traces show stationary behaviours, and not crawling or stooping, is evidenced by the symmetrical position of the footprints and impressions of an ischial callosity (the soft-tissue covering the posterior prong of the dinosaur pelvis). These pelvic traces show that the body was in contact with the ground when these traces were made, and that it was not being dragged forwards. Clearly, these animals were, at least partly, letting the ground take some of their weight.
We don't just have to look to trace fossils for evidence of crouching behaviour. On rare occasions, remains of dinosaurs are found that were more-or-less entombed alive in ash or sediment, revealing details of their postures at time of death. Famous examples of such occurrences include several troodontids (Russell and Dong 1993; Xu and Norell 2004; Gao et al. 2012) and protoceratopsids (Fastovsky et al. 1997). These also consistently show dinosaurs resting on their bellies in crouched postures, legs folded up either side of their bodies in a very avian manner.
Secondly, it's interesting that we only sometimes see hand prints associated with crouching traces (Milner et al. 2009). When we do, we tend to see evidence of the palms and digits, not of whole forearms, as we might expect from a fully resting, lying animal. So are these animals actually lying down, or just sitting? Have they crouched down to truly rest, or are they performing some other behaviour (e.g. foraging, preening etc.)? I find it interesting that crouching traces can occur multiple times within trackways (Lockley et al. 2003), and that others show evidence of animals shifting weight and changing direction. Such instances seem to record sitting, but still 'active' individuals. Studies of modern animal behaviour are relevant here. When researching bird sleeping postures, I found Almaner and Ball (1983) had similar misgivings about the idea of immobile birds being 'inactive' or merely 'resting'. Based on their observations, they divided avian 'loafing' behaviour (that is, behaviour adopted when the bird is generally immobile) into multiple types of activity, of which only one is resting. Looking through their categories of loafing behaviour (below), none seem outlandish when applied to dinosaurs and I wonder what those prints made by stationary, crouched dinosaurs really represent: resting is really only one option. It may be that further examination of 'resting' traces can turn up more information. That said, I'm aware of slightly frustrating experiments with modern emus where even optimal substrates for track formation do not record additional trace evidence of activities like feeding from crouched positions (Milàn 2006). But, hey, we can still be optimistic that more data and insights will come in time.
|What it means to be a stationary bird. Clearly, being crouched and immobile does not always mean 'resting'. From Almaner and Ball (1983).|
On a related note, I also wonder how we would identify a dinosaur that died deliberately resting on its side rather than being moved into that pose by taphonomic processes. Most animals require effort to remain vertical, be it crouched or otherwise, and it's obvious when we find crouching dinosaurs that their pose reflects something of their final behaviours. But how do we distinguish a dinosaur preserved having a nap on its side from one that simply died and fell over, or was washed up on a riverbank or whatever?
All this considered, my point here is not that these data are meaningless when it comes to discussions of dinosaur resting postures. They clearly show that many Mesozoic dinosaurs did naturally crouch in an avian-like manner, and there's no problem with assuming this has some bearing on resting poses. But I do not think this data is without complications, nor that it is complete enough to tell us the whole story here. We probably need to look elsewhere for additional information.
The search for modern analogues
|Torvosaurus tanneri in controversial 'reclining on a recline' pose.|
But what about other species? We might look to other reptiles for further insight here. Lizards, turtles and crocodylians are like birds in that they rest on their bellies, although they tend to be less fussy about the placement of their limbs (I often find my own pet reptiles looking like they just flopped down mid-step, legs and arms at all sorts of angles. It doesn't look comfortable, but I guess it must be). But do these animals really have an alternative? Their bodies are very broad but shallow, and their limbs project laterally from the torso. It's hard to imagine them achieving a stable resting posture by doing anything other than lying on their bellies.
The body shapes of living reptiles are pretty distinct from those of sauropods or many ornithischians, and I don't think these animals provide much assistance with our inquiry. For these groups, a case can be made for their basic form being more akin to those of modern mammals than any living reptile. Like mammals, they tend to have deep, narrow chests, (see illustrations in Paul 2010 and Goldfinger 2005), and many lack the rigid structural bracing and expansive chest muscles that we see in birds. For some dinosaur groups, the limbs of large land mammals are better models than the light, flexible limbs of birds, and the fact many mammals are quadrupedal is also of utility here. The relative weight of mammalian heads, and flexibility of their necks, may be more comparable to some dinosaurian bauplans than avian ones too, and mammals are also our best (and only) modern analogue of larger Mesozoic dinosaur body masses. The latter is important to this discussion as shifting weight around between standing and reclining, as well as considering weight bearing during the rest phase, are factors here.
All these points considered, maybe the body shapes and masses of mammals offer some of the most useful analogues for non-bipedal dinosaur resting poses and related mechanics? Mammals are, of course, far more flexible in their approach to resting than reptiles. Even large mammals like elephants, hippos, rhinos and large bovids are capable of crouching and lounging on their sides, and even modest-sized species will sometimes rest on their backs. I imagine this is because deep-chested large animals are top-heavy when crouched, so flopping over to one side is likely to be far more relaxing and stable. The fact that our largest land animals can spend hours on their sides without dying of asphyxiation is a good indication that this may not have been a concern for large dinosaurs, either. A big elephant is going to weigh as much as many big dinosaurs and, while the biggest hadrosaurs and sauropods were likely heavier, it's useful to have confirmation that 5-6 tonne creatures can lie down for extended periods without problem. I often wonder if the idea of animals crushing their lungs and other organs when lying down is a bit of a myth, or at least overstated. Even large stranded whales, weighing many times more than our largest elephants, can survive for days on land before dying. The fact is most beached whales die of complications related to the injuries and diseases that led to their stranding in the first place, and this generally happens long before their lungs or other organs are crushed.
|To cheer everyone up after all that talk of dead whales, here's a male Asian elephant napping. D'aw. Photo by Wikimedia user Fruggo.|
|Resting postures of the Greater Rhea, depicted by Amlaner and Ball 1983. I recall seeing a rhea using the upper posture at Edinburgh zoo. It's... weird seeing a bird sitting like this in real life.|
Functional studies of dinosaur anatomyWe've looked at direct evidence of reposed dinosaurs and their modern analogues, which leaves functional considerations of dinosaur skeletons as our last main area of consideration for this topic: is there anything about their anatomy to suggest resting on their sides or using other postures might be prohibited? The fusion of some dinosaur vertebrae is often mentioned as a problem here, particularly the ossified tendons common to many ornithischian dinosaur groups. These are suggested to have limited the motion of the vertebral column and limited dinosaurian abilities to shift their mass/wiggle out of lounging postures. Such suggestions are probably overstating the stiffening effect of ossified tendons. As a general point, it should be mentioned that ossified tendons are common across animals of all kinds, and occur in many places in their bodies. For example, they occur in the bodies of fish, in bird and human legs, along bird backs, in sauropod necks and in pterosaur forearms (e.g. Bennett 2003; Organ 2006; Organ and Adams 2010; Klein et al. 2012). Moreover, they are not necessarily anything to do with restricting skeletal motion. Sometimes the opposite seems true: they may be something to do with storing and releasing energy to increase arthrological efficiency, or simply reduce strain on musculature. Their functional roles are still being worked out, but it seems well grounded that their role varies with their position in the skeleton and their associated musculature. We also know that their histological composition varies, and this likely affects their mechanical properties too (Organ and Adams 2010).
In dinosaurs, ossified tendon distribution along the vertebral column is quite varied. As a general rule, ossified tendons occur around the hip and tail base, but they can cover many of the torso vertebrae in things like hadrosaurs. Studies suggest that their effect is to reduce vertebral motion in some planes, but they do not eliminate movement altogether (Organ 2006). The vertebrae can still move in all directions, and even relatively freely in some axes of motion, and that's likely all that was needed to enable animals to lift themselves from a non-crouching resting posture. We only need a few degrees of motion here and there to liberate a limb, or to gain better purchase on the ground, before the limb skeleton can take over in levering the body into a standing pose. For the sake of completeness, it's worth mentioning that the trunks of other dinosaurs - those without ossified tendons - were probably mobile enough for this job, too (e.g. Mallison 2010a, 2010b).
Finally, a practical consideration
|From the new ITV show "Abelisaurs do the Darnedest Things".|
So, in summary...Putting all these lines of evidence together - the limited direct fossil data, our ability to interpret that fossil data, the anatomy and behaviour of modern animals, and what we know of dinosaur anatomy - I still don't see any reason to think Mesozoic dinosaurs were constrained to crouched resting poses. I stress my use of the word 'constrained' there: as mentioned above, there is good reason to think crouching was utilised by dinosaurs for a variety of reasons, and I'm sure many of them rested in this way. Moreover, we can probably assume that most dinosaurs entering or rising from repose would have assumed a crouched position during that process. This seems fairly true of modern animals, after all. But there seems no reason to think they were incapable of other resting in other attitudes as well, such as reclining in classically 'mammalian' poses, using some of those strange ratite or galliform postures mentioned above, or doing something else entirely. It seems almost certain that different dinosaurs were suited to different poses, and different ranges of poses, when resting: maybe this is something to explore in future art.
Coming next: this:
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|Two giant azhdarchids, Arambourgiania philadelphiae, attempt to portion a troodontid. The troodontid objects.|
Many readers will be aware that these aren't the only giant azhdarchids, however. The record of these animals cannot be described as extensive, but it is sufficient to indicate that they were present across most of the world and probably not particularly rare in Late Cretaceous ecosystems. But most fossils of giant azhdarchids are unnameable on account of being too fragmentary, being represented by parts of undiagnostic anatomy, or being too poorly preserved. This makes it all the more surprising that the third named giant azhdarchid doesn't get much attention: the Maastrichtian species Arambourgiania philadelphiae, known from several bones from phosphate mines in Jordan.
I'm not sure why we generally overlook this giant. Perhaps it's because Arambourgiania - 'Arambourg's giant' - is one of those old-fashioned names which works better in translation than the original Greek. It certainly doesn't sound as evocative or exotic as Quetzalcoatlus or Hatzegopteryx. Moreover, it's the least known of the three named giants, being primarily represented by a long - 620 mm - cylindrical neck vertebra, and not much else. The other named giants are not well represented either, but we have more than a handful of bones for them, and they're represented by intuitively intriguing anatomies: giant wing skeletons, bits of skull and jaw and so on. But whatever the cause, there are reasons to consider our relative neglect of Arambourgiania as unwarranted. It may not be as well-known as Quetzalcoatlus, or as immediately intriguing as Hatzegopteryx, but if you're interested in giant azhdarchids (and, hey, who isn't?) you this animal deserves your attention just as much as the other species. Here are just three reasons why.
History has been unkind to Arambourgiania
Despite his misidentification, Arambourg made one thing very clear in his reports: his animal was big. In both his 1954 and 1959 works he wrote that this bone, fragmentary as it was, clearly indicated an animal vastly superior in size to the 7 m wingspan Pteranodon, then considered the largest flying animal of all time. This is important: as early as the 1950s Arambourgiania was being interpreted as evidence that pterosaurs with wingspans rivalling small planes once existed.
|Arambourg's (1954) illustration of the Arambourgiania vertebra as a wing metacarpal.|
Other authors missed the significance of Arambourgiania too. For instance, when writing about giant pterosaur flight in 1974, Cherrie Bramwell and G.R. Whitfield stated that Pteranodon was the largest flier ever. Ross Stein's (1975) work on a similar topic provided the same fact, and Wellnhofer's (1978) review of Pterosauria made no mention of the size of Arambourgiania. It wasn't until the 1980s and 1990s that Arambourg's interpretations finally penetrated the pterosaur research zeitgeist, but by this time a flurry of media and scientific attention had made Quetzalcoatlus 'the' giant pterosaur. Arambourgiania would eventually get more dedicated scientific treatment - including wingspan estimates - in the mid 1990s (Frey and Martill 1996; Steel 1997; Martill et al. 1998), but this did little to elevate the status of Arambourg's work and his giant in the story of giant azhdarchid research.
|Predicted size and neckage of Arambourgiania next to a Masai giraffe and a human wife. C. Arambourg predicted this 20 years before anyone else, yet we rarely give him any credit for his insight.|
Arambourgiania is more than just a neck boneIt's rarely mentioned that Arambourgiania is known from material other than just a gigantic neck bone: a smattering of other bones from the same Phosphate mines might - probably- pertain to the same species. These were re-discovered and outlined by Frey and Martill (1996), and comprise the proximal and distal end of first wing phalanx (below), and a heavily eroded bone interpreted as a second cervical vertebra. Given the uncertainty about their association with the holotype - remember that the circumstance of its collection are lost to history - Frey and Martill classified these as cf. Arambourgiania.
The wing phalanx elements however, are more interesting. For one, they're enormous, and look proportionate to the holotype vertebra when juxtaposed in a skeletal reconstruction (below). If they're not from the same individual, they must be from a very similarly sized one. Frustratingly, the wing phalanx ends are broken in a way that hints at the bone shaft bone surviving to the modern day as well, but being lost in recent times.
|Arambourgiania (known elements in white, restored, hypothetical neck length of 2.6 m indicated by grey vertebrae) compared to Quetzalcoatlus sp. Note the chunky wing finger bones.|
It might be difficult to understand why these scraps of a wing bone are exciting, but they inform us of some fundamental aspects of giant azhdarchid anatomy and wing structure. There aren't many giant pterosaurs where we have recognisable wing and neck material from the same species so, however scrappy it might be, this is already useful material for building a picture of their proportions and appearance. From a functional perspective, they are interesting in showing that wing finger of Arambourgiania articulated with the metacarpal in exactly the same way as it did in smaller pterosaurs. This is good to know, as it confirms the notion that understanding the smaller azhdarchid species is our best route to fathoming the bigger ones. And of further mechanical note is that these elements show the wing finger as proportionally robust, with a big articular surface for the metacarpal/phalanx joint and a wide space for insertion of ligaments pulling the wing open in flight. Increased robustness is a sign of greater resistance to stresses and strains, and a good indication that Arambourgiania had scaled its wing bones to be flightworthy. This is an important counterpoint to proposals from some researchers that the extreme size of giant azhdarchids rendered them flightless. Of course, these scraps of wing bone don't tell us much about flight performance or style, but they are a good indication that flight of some kind was happening in these forms.
The neck of Arambourgiania was a high point of tetrapod evolution, and we need to learn more about it
So counter-intuitive as it seems, making a neck out of tubes is a good way to produce a strong, long, lightweight skeleton, especially if it has to support heavy loads like a huge head. Pterosaurs used the same tactic to enhance their wings, and it seems azhdarchids - especially Arambourgiania - transferred some of these mechanical properties to their vertebral column. We can only guess at the exact proportions of the Arambourgiania head, but adaptations of its neck bones indicate it might have been just as large as those of its smaller cousins. While assessments like this are very basic and clearly only the tip of the iceberg as goes azhdarchid neck mechanics, they demonstrate that Arambourgiania is, and will continue to be, a critical species for understanding the neck proportions, mechanics and scaling of giant azhdarchids.
So, what I'm saying is...
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Finally, my long promised palaeoart book Recreating an Age of Reptiles is available from online retailers! Conceived as a short, 'how long can it take to publish a print-on-demand book where I have full control?' sort of project, today marks the end of the year of design, illustration and writing work it actually took to take this broad, palaeoart-led look at various parts of the Mesozoic. The result is a Letter page-sized (that's 21.59 x 27.94 cm) full-colour paperback with 108 pages of text and imagery, and over 90 bits of artwork. About 20% of the artwork has not been published anywhere before, at least not in entirety, and virtually none of the pictures have been featured in other publications. So if you're after some new entries on your palaeoart bookshelf, or hard copies of images of mine that you've seen around the internet, this might be the book for you. You can access a preview of the book interior via its page at Lulu.com.
|The opening spread of the azhdarchid pterosaur section. This is one of three sections featuring flying reptiles.|
|Brontosmash! needs a double page spread.|
So, where can you buy it from, and how much is it?The cover price for Recreating an Age of Reptiles is £26, and it's available now, direct from Lulu.com (below). You can also buy it at all major online book stores (e.g. Amazon, Barnes and Noble etc.). But before you click the Amazon link, note that Lulu.com is, and will always be, the cheapest place to buy Recreating an Age of Reptiles. I've set a 5% discount at their store which means it's retailing for £24.70, not £26. I'll be honest about why I've set this incentive: major retailers take 50% of sale profits before the rest can be divided up among printers, publishers and authors, which means book authors are not left with much from their sales. Lulu offers the same shop service as anywhere else online (and you can pay with Paypal, too) and their service, in my experience, is swift and efficient - you should have the book within a week from ordering.
support me on Patreon, a copy of the book being a reward for the highest support tier. This copy will be signed and doodled on if requested. If you have any requests for a small sketch in the front pages, please let me know when you place your order!
The final way is to buy a signed and doodled copy through my website store. These are a bit more expensive than the unsigned copy, because there's two sets of shipping to factor (once to me, and then again to you) but hopefully not too steep at £30. These will be on sale any day now. As above, if you have any requests for a small sketch along with my signature please let me know when you place your order!
I'll have more info and promotional material for the book here in a few days - in the meantime, if you have any comments or questions, be sure to ask them in the comment field below, on Facebook or Twitter (#RecARep is the Recreating an Age of Reptiles hashtag). And for those who buy the book, I hope you enjoy it!
If you'd like a more in-depth introduction to the project and enjoy the experience of disembodied voices narrating over slides, why not make a cup of tea and watch this 24 minute book launch video? It features some of the new art, explains why the book has such an old-timey title, and outlines some of the palaeoart philosophising that takes place therein.
Minor update (06/07/16): Thanks to Andrea Cau, a few additional citations and points of discussion have been made below - the thrust and arguments of the post are the same, but the context is improved. Thanks Andrea!
|Hypuronector limnaios restored as a glider. Have palaeontologists been smoking something of variable legality, or is there some basis to this?|
Because the Triassic was evolution's drug-fuelled, rebellious college days, it can't be considered shocking to learn that there's a drepanosaur species which is to drepanosaurs what they are to everything else. This distinctive, strange, and controversial species is Hypuronector limnaios (above). Reasonably good fossils of this small (c. 12 cm long) animal have been known for decades from upper Triassic deposits of New Jersey, but it received its name only relatively recently (Colbert and Olsen 2001). Hypuronector is often regarded as a swimming creature because of its dorsoventrally expanded, 'leaf-shaped' tail which lacks a hooked or prehensile termination (Colbert and Olsen 2001). Its tail is remarkable for the enormous chevrons (prongs of bone projecting downwards from the underside of tail vertebrae) which extend far below and behind their vertebra of origin to create the majority of the tail depth and its 'leaf-like' profile. Some authors have likened the outline of the tail skeleton to the body shapes of gymntoid or gymnarchid fish and suggested that it propelled Hypuronector through the deep, freshwater lakes its fossils were buried in, perhaps in a newt- or crocodile-like fashion (Colbert and Olsen 2001). Although possessing unusually long legs relative to other drepanosaurs and swimming animals, it's been argued that these were also related to an aquatic lifestyle. Specifically, it's suggested that they held the long, deep tail off the ground during terrestrial bouts, the tail apparently being incapable of elevation at its base (Colbert and Olsen 2001). This aquatic Hypuronector hypothesis has been around for some time. The animal was informally known as the 'deep tailed swimmer' in the 1980s (Fraser and Renesto 2005) and this moniker was transferred more or less entirely to its scientific name in 2001: loosely translated, Hypuronector means 'deep-tailed lake swimmer'.
|Hypuronector limnaios skeletal reconstruction, from Renesto et al. 2010. Scale represents 10 mm.|
The aquatic Hypuronector hypothesis under scrutiny
|Holotype of Hypuronector limnaios, a partial skeleton with the 'paddle tail' (left), disarticulated torso and bits of limb and limb girdle. From Colbert and Olsen (2001).|
It stands to reason that Hypuronector would have swum like a crocodylian, newt or swimming lizard, where waves of lateral undulation in the tail generate forward thrust (Colbert and Olsen 2001). This requires tail anatomy which can accommodate a lot of lateral motion, and it's here that Renesto et al. (2010) suggest we hit a major issue. The caudal vertebrae of Hypuronector seem to permit some movement at the base and tip of the tail, but the mid-tail was pretty stiff. This is because the zygaopophyeses - processes of bone that overlap neighbouring vertebrae to guide their motion - are very long and have steep articular surfaces (below). In simple terms, they seem to have 'clamped' their adjacent vertebrae rather than - as expected for an undulatory tail swimmer - provided flat, horizontal surfaces for the vertebrae to slide over.
Further rigidity is provided by those amazing chevrons (Renesto et al. 2010). These rearward-projecting bones underlie the articulations of the adjacent 7-8 vertebrae, meaning any lateral motion at the vertebral joints had to overcome the stiffness of the 7-8 bony rods hanging beneath them. Although thin bones are somewhat compliant and the Hypuronector chevrons may have been flexible to a degree, it's difficult to see their arrangement as optimised for sculling habits: they may made the tail more paddle shaped, but to obvious detriment of tail flexibility and sculling potential. Indeed, we have to note that this configuration is very similar to biological structures adapted to resist bending. Tetrapod wings are a good example: the arrangement of bat fingers, pterosaur structural fibres and bird feather shafts with respect to the wing bones echoes the chevron distribution in Hypuronector. By contrast, deep-tailed swimmers, like crocodylians and newts, have chevrons which are short, robust, and do not significantly underlie neighbouring vertebrae. They are ideal structures for anchoring tail musculature, increasing tail depth and not interfering with tail motion. I have to agree with Renesto et al. (2010) that the potential of the Hypuronector tail as a swimming organ seems limited.
|Hypuronector limnaios posterior trunk (left) and tail base (right) - note elevation of the latter with respect to the former, and the significant overlap of the zygapophyses. From Renesto et al. 2010, scale represents 10 mm.|
Maybe Hyperonector isn't 'the weirdo drepanosaur 'after all?Taken collectively, these points about tail shape, tail arthrology and limb size must be viewed as problematic for the aquatic Hypuronector hypothesis, and maybe we should see if there are other interpretations of Hypuronector lifestyle which are more in tune with its anatomy. A good strategy for understanding strange fossil animals is putting the controversial, weird bits of anatomy to the side and first focusing on the more reliably interpreted components. With that said, let's ignore the controversial tail of Hypuronector for a moment and look at its limbs, limb girdles and trunk anatomy. As with all drepanosaurs, the shoulder and hip bones of Hypuronector are very tall and somewhat reminiscent of the limb girdles of chameleons (Renesto et al. 2010). It is thought both limb sets were highly mobile, although the drepanosauromorph fusion of the pectoral girdle into one solid structure, as opposed to having two separate halves like chameleons, would limit forelimb reach somewhat. The limbs were likely held in a sprawling pose and, because the femora and humeri are greatly elongated, Hypuronector likely had a wide, stable base to walk and stand on.
|Bits and pieces of AMNH Hypuronctor specimens, including the only known cranial material (mandible, A-C) and the ventral view of a trunk and pectoral skeleton. Note the huge, curving ribs. From Renesto et al. 2010.|
It can be seen that Hypuronector trunk and limb anatomy matches pretty well with what we see in other drepanosaurs: powerful torsos and mobile limbs that seem well suited to walking and climbing. We might view its limb elongation as an adaptation to climbing, the increased length of the upper limb segments simultaneously increasing stability and enhancing reach while also keeping the centre of mass close to the substrate. Perhaps more surprisingly, Hypuronector is also similar to other drepanosaurs in certain aspects of tail anatomy. Although its tail has a different overall shape and lacks the derived tail-tips of true drepanosaurids, it shares the specifics of drepanosaur tail motion - flexible base and tip, rigid mid-length - with the rest of the group (Renesto et al. 2010). So perhaps the tail of Hypuronector was just a simpler, oddly-shaped variant on the drepanosauromorph tail and used for similar purposes: stability when climbing (a simple prop can aid traction, balance and recovery from accident), a brace when rearing to dig and feed, or simply for showing off (Renesto et al. 2010).
Putting these lines of evidence together, several authors have started to interpret Hypuronector as a more 'typical' drepanosaur, albeit a less-specialised species that lived like a modern arboreal lizard rather than a reptilian tree pangolin or pygmy anteater (Spielmann et al. 2006; Renesto et al. 2010). If this is true, we might view the shape of its tail as a mechanical red-herring, something which seems more important to Hypuronector behaviour than it actually was. Perhaps it had no more significance to locomotion and behaviour than do the cranial ornaments of dinosaurs and pterosaurs, structures which most now agree were more to do with communication and display than the mechanics of day-to-day life.
Yes yes yes, but we're here for the gliding stuff
|Which might have been handy if the initial glide trajectory was what glider pilots call 'less than ideal'|
Of course, it's worth stressing that any gliding drepanosaur is hypothetical at this stage, but we should not take this as reason to dismiss the idea out of hand. In addition to the evidence mentioned above, consider that many, perhaps all drepanosauromorphs seem to have been climbers of one kind or another, and we know from extant faunas that the step from climbing to gliding is often a short one (Renesto 2000). It's really not crazy to think extinct lineages were any less able to develop gliding forms than our modern ones, and drepanosaurs were exapted for gliding flight in many ways. Their skulls had large brains and overlapping visual fields (Renesto and Dalla Vecchia 2005) (ideal for judging distance and processing flight data); they were generally small animals with hollow limb bones (lightweight); their torsos were stiffened and reinforced (aids stability); their limbs were powerfully muscled and highly mobile (control of aerofoils) and their deep, strong tails might be ideal rudders and stabilisers. And as bizarre as it may seem to be discussing the possibility of gliding in an animal only known from bones, recall that pterosaurs were identified as flying animals in the early 1800s long before we discovered fossil remains of their wing membranes: we can identify flying animals if we look carefully enough at their bones. The challenge now is to see if we can test these ideas, perhaps carefully comparing the limb anatomy and myological signatures of Hypuronector with other drepanosaurs, modelling the effects that crazy tail has on a falling animal and so on. We can also look for Renesto et al.'s membranes on Hypuronector fossils, examining them with UV light and being extra-careful when preparing future Hypuronector specimens: experience with other delicate reptile specimens shows that it helps to know where to expect soft tissue when removing matrix.
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|Pteranodon longiceps, Pteranodon sp. or something else entirely? In recent years one of our most famous and abundant pterosaurs has been carved up into multiple species, but is this overzealous taxonomic splitting, or is there more to it than that?|
A series of papers documenting Pteranodon anatomy, variation and stratigraphy, all penned by pterosaur expert S. Christopher Bennett during the 1980s-2000s, have made this pterosaur one of the best understood of all flying reptiles (perhaps the most important entries in this series are Bennett 1992, 1993, 1994, 2001a, 2001b). These publications are the result of examining several hundred Pteranodon specimens and are among the most significant and comprehensive contributions to pterosaur literature in modern times. I recommend them to any students of vertebrate palaeontology: even if you don't agree with their conclusions, they're great examples of clear writing, of hypotheses being established and tested, and of large amounts of data being presented clearly and logically.
|Skeletal restorations of P. longiceps male (the larger animal) and female morphs, based on Bennett (1992). Illustration from Witton (2013).|
But then things got a complexGiven the established status of Pteranodon taxonomy it came as something of surprise when, in 2010, a counterargument to Bennett's interpretation of Pteranodon was published. Another big name in modern pterosaur research, Alexander Kellner, proposed that Bennett's Pteranodon was in fact a 'complex' of at least four species (perhaps five) in three genera (Kellner 2010). Kellner's alternative scheme suggested that the giant, swollen-crested sternbergi was different enough from longiceps to warrant a separate genus, and resurrected the 'subgenus'Geosternbergia for this purpose (giving us the rather daft name Geosternbergia sternbergi). A second Geosternbergia species was proposed for a partial skull referred to P. longiceps by Bennett (1994), which Kellner named G. maiseyi.Another skull, this one with a broken crest but the best preserved rostrum of any giant Pteranodon specimen, was said to represent a third pteranodontid genus, the deep-snouted Dawndraco kanzai. Finally, although not naming a new taxon, Kellner (2010) singled out another P. longiceps specimen as being distinct from this species, arguing that this long-crested specimen has a crest which is too upright to be referred to longiceps: he referred this simply to Pteranodon sp. for now. You can see these skulls, and how they contrast with Bennett's older scheme, below.
|Differing interpretations of some important Pteranodon skulls. Blue text and panelling reflects the Bennett (1994) interpretation of Pteranodon skull taxonomy, green text shows where Kellner (2010) differs. Skull images borrowed from Bennett (1994).|
I've been asked about the 'Pteranodon complex' several times and thought it was time to share my thoughts here. I normally avoid talking about detailed taxonomy because I'm aware how dry it can be, but the Pteranodon controversy is pretty interesting. There are lot of strands of data to consider, some philosophising about palaeontology itself, and - if nothing else - the reality about the fossils behind Pteranodon might be of interest. This is only a summary of course - if you're interested, you really need to check out the papers cited below for the full details.
How understanding hundreds of Pteranodon specimens hinges on a handful of important ones
|The holotype skull of Pteranodon longiceps, the only Pteranodon specimen which can be objectively referred to the genus. This skull is from a small (presumed female) morph. From Eaton 1910.|
Bennett's characterisation may seem quite broad, maybe even simplistic, but there's a reason for that: no two Pteranodon crest specimens are entirely alike and none of our better, larger skull specimens are complete (below). We have some excellent and complete smaller skulls (above), and several incomplete large specimens, but any visage you see of a long skulled, long-crested Pteranodon fossil is an interpretation of fragmentary specimens. Bennett's (1994) taxonomy reflects this, using relatively broad characters to separate the species because the material ultimately offers limited scope for detailed comparison or augmentation with other characters. The fact that the crests differ somewhat within Bennett's species is explained by their likely role in visual communication rather than biomechanics (Bennett 1992; Tomkins et al. 2010): such structures are often far more variable in appearance, and sensitive to factors like ontogeny, than strictly 'functional' anatomies.
It's not just taphonomic and diagenetic effects which are of concern: there are palaeobiological trends to consider, too. For example, Kellner (2010) uses the breadth of the crest base as a diagnostic feature for both Dawndraco and G. maiseyi, noting that the former has a crest base located largely behind the eye socket, while the latter is expanded to erupt well in front of the orbital region. But Bennett (1994) gives reason to think that crest base size is linked to growth and size, not taxonomy. As can be seen above, there's a steady correlation between crest base size and skull size: larger skulls have much thicker crest bases extending far in front of the orbit than smaller skulls (Bennett 1994, 2001a). Although Kellner (2010) mentions that Dawndraco is a relatively mature specimen, and thus maybe unlikely to change its crest size, there's no discussion of the fact that the Dawndraco skull is quite a bit smaller than some other 'large'Pteranodon skulls (below). The fact this small skull has a smaller crest is, of course, consistent with Bennett's crest scaling hypothesis. Similarly, the wide-crested maiseyi skull meets Bennett's predictions that it should - as a big individual - also have a relatively large crest base.
|The Dawndraco skull compared to fragmentary Pteranodon sp. jaw tips. Note how the subparallel dorsal and ventral margins and (predicted) Dawndracro overbite are present in other Pteranodon fossils. Note that some small Pteranodonhave overbites too. Drawings after Bennett (1994).|
Pteranodon stratigraphy and the significance (or not) of geological boundariesBoth Bennett's and Kellner's taxonomies consider Pteranodon distribution through the Niobrara Formation and neighbouring rock units, but there are fundamental differences in how they treat this data. Bennett's (1994) approach sees morphology trump stratigraphy in that the ranges of his species are dictated wholly by specimen anatomy. This is essentially the approach typically taken by biostratigraphers, where it is considered (and relied upon) that species distribution is not linked to our designation of rock units. In this scheme, it doesn't matter where the specimen occurs, but what it looks like that matters. The fact that all the 'sternbergi morphs' occur at the base of the Smoky Hill Chalk Member, and all the 'longiceps morphs' occur at the top (and somewhat beyond - see below) is the basis for Bennett's (1994) idea that our Pteranodon sample is a single, evolving population which entered the fossil record as sternbergi, and left as longiceps. The fact that these species do not overlap can be viewed as helping the verify the Pteranodon chronospecies hypothesis.
Kellner (2010) makes specific mention of the fact that neither the Dawndraco or maiseyi skulls are from the same horizons as other Pteranodon type material (below). Particular attention is drawn to maiseyi, which comes from the Sharon Springs Formation: a unit two formations above the Niobrara Formation and its glut of Pteranodon material. Of this, Kellner states: "One could argue that the morphological differences of Geosternbergia maiseyi might be due to ontogeny, individual variation or even sexual dimorphism, but there is a considerable time gap between these [pteranodontid] species that never co-existed." (Kellner 2010, p. 1078). The implication here is that there is a stratigraphic limit to when similar-looking animals might be considered conspecific, and that morphological similarity is eventually overruled by provenance.
|Pteranodons in time - click to embiggen and see full details. Grey lines show distribution of key Pteranodon|
More specific concerns with the 'Pteranodon complex' approach to stratigraphy is that its perceived issue with Pteranodon ranges are not mirrored by those who work on other Niobrara Formation vertebrates. From fish to marine reptiles, it's widely thought that many Niobrara species persisted through big chunks of the three million year period recorded by the Smoky Hill Chalk Member and Pierre Shale Group (e.g. Everhart 2005; Carpenter 2008). If large swathes of the Smoky Hill Chalk fauna can survive over long periods of time, why can't Pteranodon species? It is noteworthy here that Hargrave (2007) identified new, potentially diagnostic Pteranodon longiceps bones from the Pierre Shale. If so, this bolsters older suggestions that longiceps occurs above the Niobrara Chalk (Kellner (2010) was unconvinced of their referral to longiceps, however). We might also note that the 'Pteranodon complex' taxa accord less with stratigraphy than alternatives, in that Geosternbergia disappears during the interval represented by the upper Smoky Hill Chalk and Gammon Ferruginous Formation, only to reappear in Sharon Springs beds. This is despite there being a higher number of skulls the upper Smoky Hill than any other Pteranodon bearing interval (Bennett 1994). This isn't an insurmountably complex distribution of course, but in terms of parsimony, Bennett's (1994) scheme must be seen as simpler and more congruent with stratigraphic data.
'Pteranodon complex', or Pteranodon simple?
It would perhaps be remiss to outline all this without giving my own take on this shake up of Pteranodon taxonomy. In my 2013 book I said I preferred Bennett's (1994) scheme and followed it accordingly and, revisiting this debate several years later has not changed my mind. I stress that I'm not 'against' the idea of more Pteranodon species, just that - in my opinion - the evidence points to Pteranodon containing longiceps and sternbergi, and that these species are each others closest relatives and might as well stay congeneric in Pteranodon. For reasons outlined above I find the stratigraphic arguments about separating these taxa unconvincing, and I don't think the morphological arguments are developed enough yet to overturn those for synonymy.
Concerning the specific taxa, the Dawndraco skull seems to be about right for a small 'male morph'P. sternbergi, and probably mostly seems atypical because of it's relatively completeness. Most large Pteranodon probably have those big rostra (you'll note that all my paintings of large Pteranodon, like that above and here, have this feature). What I've seen of its postcrania is extremely Pteranodon-like too, right down to its peculiar, highly characteristic tail (see Kellner 2010, p. 1074). I can appreciate why some folks might consider the maiseyi specimen a different taxon because of its seemingly unusual crest. However, the fact the leading crest edge is relatively complete but does not swell forwards means it is not particularly sternbergi-like, despite Kellner's (2010) suggestion that the maiseyi specimen is more closely related to sternbergi than anything else (Kellner 2010). Indeed, as preserved, the maiseyi crest meets the criteria of longiceps provided by Bennett (1994) as well as his predictions that it should have a huge crest base because of its large overall skull size. Moreover, the posterior and dorsal crest margins are broken: there is greater potential for the complete maiseyi crest to be more longiceps-like (longer, posteriorly directed) than sternbergi-like (tall, expanded forwards).
As for the large longiceps crest referred to Pteranodonsp., the specimen is not only (and obviously) very incomplete but the crest base is badly deformed, and I find it difficult to orientate the specimen against other skulls to determine the crest angle. There are suggestions that the crest base is too tall over the orbit to be longiceps (Kellner 2010) but, again, this region seems to change a lot with size and this specimen seems to have belonged to a big skull (judging by the orbit proportions): this needs to be considered carefully. The crest shape itself is generally longiceps-like, of course, and I suspect this specimen is just a big, mature version of this species.
|So cheer up matey, you might not be a 'sp.' after all.|
This blog post on the 'Pteranodon complex' was made less complex because of support from PatreonThe paintings and words featured here are sponsored by a most excellent group of people, my Patreon backers. Supporting my blog from $1 a month helps me produce researched and detailed articles with paintings to accompany them, and in return you get access to bonus blog content: additional commentary, in-progress sneak-previews of paintings, high-resolution artwork, and even free prints. For this post, we'll be taking a look at one of the most interesting, and barely ever mentioned parts of Pteranodon anatomy. If you want to know what it is, head over to Patreon to get access!
|Giant, Oligocene rhinocerotoids Paraceratherium transouralicum engage in some early morning flirting. Because, in rhino speak, playing hard to get involves shoulder barges and head-butts.|
The obligatory note on nomenclatureIt almost seems tradition that any article or paper on indricotherines requires an aside on their confused taxonomy. As has been the case for decades now, the taxonomy and systematic nomenclature of these giant rhinocerotoids are a matter of ongoing discussion. It is widely appreciated that several giant indricotherine species from roughly contemporaneous Oligocene Asian sediments can be identified, but how many species they represent, and how they are related to each other, is not clear. At least seven generic titles and many more species names have been given to the largest of these animals over the years (Indricotherium and Baluchitherium are perhaps the most famous generic labels), but some authors (e.g. Lucas and Sobus 1989, Prothero 2013) tidy all or most of these taxa into three species of the oldest established genus, Paraceratherium. Arguments persist, however, that at least one other, perhaps slightly smaller genus existed, Dzungariotherium (Qiu and Wang 2007). Geologically older indricotherine genera such as the Eocene Urtinotherium are also wrapped into these discussions as remains attributed to the Oligocene genera are sometimes argued as having greater affinity to these older taxa (Prothero 2013).
This confusion is sometimes framed as a 'lumper/splitter' philosophical distinction, but it does not help that the fossil record of these giant rhinocerotoids is far from exemplar: giant indricotherine specimens can be fragmentary, of starkly contrasting size with one another, and many suffer from distortion. The fact that 20th century indricotherine science developed with Asian and American teams working largely in isolation, with limited access to certain specimens and literature, has also contributed to the confused history of this group. Those interested in the history of indricothere taxonomy should check out Prothero (2013) for an overview. For now, it will serve us to simply state that the best known, biggest and most famous of these animals currently resides as the taxonomic address of Paraceratherium transouralicum. This is the species most of us think of as 'the' giant indriotherine as well as the taxon that has carried both the Indricotherium and Baluchitherium label at one time or another. It's also the focus of most artwork of giant rhinoceratoids, and thus forms our primary interest here.
Giant rhino, bulky giraffe or giant workhorse?One reason we see such variation in indricotherine appearance is that researchers have produced vastly different interpretations of its anatomy in the last 100 years. But unlike, say, dinosaurs, where older reconstructions have been (for the most part) abandoned in favour of newer, more accurate interpretations, educators and researchers continue to publish skeletal reconstructions published in the 20s and 30s despite our improved knowledge of indricotherine anatomy, documented criticisms of these older works, and the availability of more modern, theoretically better-informed reconstructions.
Many readers may be aware that the first reconstruction of Paraceratherium, published by Osborn (1923a),showed a form not too far off a giant rhinoceros - a heavyset, short-necked animal with a deep torso and short legs. Osborn published a revised version almost immediately after his first effort, which had a much longer neck and longer legs thanks to data provided by additional fossil material (Osborn 1923b). A shorter-necked version was then produced by Granger and Gregory (1935, 1936), who scaled the remains of numerous, differently-sized individuals from a range of collections to create their robust, gigantic take on indricotherine anatomy. Although this reconstruction has been quite influential, Fortelius and Kappelman (1993) have been critical of the scaling methods used by Granger and Gregory, calling their interpretation 'a highly speculative creation indeed'.
|Paraceratherium has been variably reconstructed over the years, with particular disagreement over how long the neck was compared to the body. So far as I can tell, a consensus on the life appearance of these animals has yet to be reached.|
And so we turn to another indricotherine skeletal reconstruction, produced by Paul (1997). This restoration incorporated data from the same specimens used in the efforts above and came out somewhat 'averaged' between the more heavyset restorations of the early 20th century and the gracile interpretation of the 1950s. It looks, in overall form, more like a giant workhorse than it does a giant rhino or bulky giraffe. Paul (1997) provides some discussion of the reconstruction process - this is worth a read if you're interested in the life appearance of Paraceratherium and its relatives. Paul's interpretation has, to my knowledge, escaped criticism to date and, to the contrary, Larramendi (2016) described this reconstruction as 'accurate', although did not elaborate on why it should be considered superior to older efforts.
The million dollar question here is obvious: which one of these different takes on Paraceratherium is 'right'? To be honest, I'm not sure. The situation is compounded by the fact that a lot of indricotherine literature is obscure, that the specimens fragmentary and that many of them await description. I was hoping that Donald Prothero's recent (2013) book Rhinoceros Giants, which is solely dedicated to Paraceratherium, would provide some insight on this matter, but it's not a great help here - it provides no real evaluation on the different reconstructions and does not even mention Paul's 1997 effort. My work above is primarily based on Paul's (1997) skeletal but this is largely because of principle rather than real insight. Paul's work is the most modern and, of course, he's made a career out of reliably reconstructing extinct animals. The brief endorsement from Larramendi (2016) helps here too, of course, but a longer discussion of the relative merits and detriments of each interpretation would be useful. Opinions from others with more insight into this matter are welcome in the comments below.
A tapir-like proboscis... on a rhino?Turning our attention to the face, did Paraceratherium and its relatives have relatively short-lipped faces like those of rhinos, or long, mobile proboscides like their more distant relatives, the tapirs? Despite mammal lips and nasal tissues being highly fleshly and thus only rarely entering the fossil record, this is a surprisingly easy question to answer. Whether rhino, tapir or anything else, a suite of osteological characters seem to correlate well with the presence of proboscides. Briefly summarised, these are: narrow snouts; retraction of the nasal openings towards the orbits; the presence of large muscle scars, bony knobs and other muscle attachment markers around the nasal opening (particularly in the dorsal region); retraction of the nasal bone (the 'roof' of of the nasal opening); deepening of the premaxillary bone (the bone making the jaw tip); anterior migration of the orbit; a large intraorbital canal (a foramen situated in the cheek region, just in front of the eye - it houses the nerves and blood vessels for our anterior face muscles); and strengthening of the posterior skull regions related to supporting the weight of the head on the neck (Wall 1980). Note that the criteria for elephant-like trunks are similar, but slightly different.
|Paraceratherium transouralicum (formerly Baluchitherium grangeri) skull in dorsal, lateral and ventral views. Note features around the skull anterior linked to proboscis development (see text). From Osborn (1923b).|
And big, elephant-like ears, right?Finally, let's tackle the component that everyone now mentions about indricotheres since seeing the Carl Buell's cover art for Donald Prothero's Rhinoceros Giants:
|Indiana University Press.|
"...indricotheres were larger in body mass than any living elephant and almost certainly had problems regulating their body heat at such large size. Elephants must do all they can to increase the surface area of their bodies to release as much excess heat as possible, which is why they have huge fan-like ears full of blood vessels that are essentially giant radiators. Given the huge size of indricotheres, it seems likely that they too should have had elephant-like ears, or at least very large ears of some shape, much larger than they are usually drawn."
The text continues to suggest that this appearance is not without anatomical support, the prominence of the mastoid and paroccipital processes (projections of bone situated behind the ear opening, adjacent to the posterior surface of the skull) being similar to the condition in certain elephants and mastodonts, and therefore indicative of large, flappy ears (Prothero 2013).
I have mixed feelings about this reconstruction. I like it for two reasons. The first is that it's nice to see indricotheres being distanced from their depiction as giant, long-necked rhinoceroses - again, it's not unreasonable to think they may have looked quite different in to modern rhinocerotids in many aspects. I also like these ears for being an All Yesterdays-style speculation on soft-tissue adaptations in extinct species. If we can use this as an excuse to give fat stores to desert sauropods or fuzzy hides to Arctic ceratopsids, then we can give large ears to giant rhinoceratoids.
On the other hand, I'm not convinced that they're as likely as Rhinoceros Giants suggests. It's clear from our modern fauna that ear size does not correlate with body mass in terrestrial mammals. By this logic many rhinos and giraffes should have proportionally large ears too, which they evidently do not. We also have to consider that even larger animals than indricotheres, dinosaurs, almost certainly got by without giant ears to help lose heat. And yes, while dinosaurs may have used different metabolic strategies to mammals, one inescapable consequence of giant size is a constant high body temperature. At least some investigations into the proportions of large dinosaurs suggest that development of their features - such as sauropod necks - were not driven by thermoregulatory pressures (Henderson 2013).
We should also consider the unusual nature of elephant thermoregulation: they are not typical mammals when it comes to controlling body heat. For one, they're atypically compact compared to other large mammals because they have extremely short necks, giant, round heads, and big, rotund torsos. This is a suboptimal bauplan for thermoregulation because it minimises surface area with respect to volume, and thus reduces the available area for elephants to dump excess heat. Moreover, unlike most mammals, they lack sweat glands (Wright and Luck 1984), do not pant, and they live in climates which are so warm that for much of the day they cannot shed heat through simple convection, big ears or not (Weissenböck et al. 2012). Elephants can, of course, regulate their temperature, but they need to employ different strategies to the rest of us mammals. These include maintaining moist skin with mud bathing and trunk spraying (Wright and Luck 1984), maintaining a sparse set of body hair to aid thermal escape (Myhrvold et al. 2012), using heterothermy (Weissenböck et al. 2012), the development of 'thermal windows' in their skin (Weissenböck et al. 2010), having loose and highly wrinkled skin to boost surface area and - of course - fanning their blood-vessel rich ears to help lose heat, when ambient temperatures are low enough for this to make a difference.
So...Putting all this together, it seems that there might be less need for uncertainty about indricothere appearance than our various artworks suggest. We should be saying 'yes' to some sort of proboscis, and 'probably not' to big ears (or, at least, 'there's no reason for them'). The elephant (or, giant rhino, if you prefer) in the room is the proportion issue, and it would be good to see folks who really know rhinocerotoid anatomy pore over those various reconstructions to ascertain which (if any) are the best representation of indricotherine form.
Next time: either the Next Big (but also kinda small) Thing in pterosaur research, or another trip to the Triassic.
Big rhinos need big support - thank goodness for PatreonThe paintings and words featured here are sponsored by another group of (metaphorically) giant mammals, my Patreon backers. Supporting my blog from $1 a month helps me produce researched and detailed articles with paintings to accompany them, and in return you get access to bonus blog content: additional commentary, in-progress sneak-previews of paintings, high-resolution artwork, and even free prints. For this post, we'll be taking a further look at the anatomy of the Paracertherium in my painting, above. Why do they have little manes and stripy faces? Are those child rhinos at the back a bit fuzzy? And why do the main animals look like they're fighting? Head over, and sign up to Patreon to get access to this and the rest of my exclusive content!
As the Cretaceous fossil record enters its final two stages - the Campanian and Maastrichtian - several unusual things seem to happen in the world of flying reptiles. Firstly, we see the end result of a steady drop off in pterosaur diversity leaving only azhdarchids - those often long-necked, long faced animals that we cover here with some regularity - with a strong, widespread fossil record. It's known that nyctosaurids and (thanks to recent discoveries) perhaps pteranodontids survived until the very end of the Mesozoic in at least two locations, but azhdarchids are globally distributed and dominate the pterosaur fossil record at this time. The overwhelming precedence of azhdarchids in the Late Cretaceous is an anomaly: at no other point in the pterosaur fossil record does one clade feature so prominently.
Secondly, Campanian and Maastrichtian pterosaurs are, without exception, pretty big animals. Many species from this time are renowned for their gigantic size: it's these stages which give us the famous 10 m wingspan, 250 kg colossi like Quetzalcoatlus,Arambourgianiaand Hatzegopteryx, as well as a number of other giant azhdarchids which are too poorly known for generic titles. Coinciding with the evolution of the giants is a loss of small pterosaur taxa - those animals less than 2.5 m across the wings which are present, more-or-less, throughout the rest of pterosaur history. This shift in body size is sometimes interpreted as pterosaurs demonstrating 'Cope's Rule', the somewhat controversial proposal that species evolve towards large body size over time (Hone and Benton 2007; Benson et al. 2014). It's argued by some that competition from birds may be the driver behind this trend, as early avians fought small flying reptiles for ecological space and ultimately forced pterosaurs into larger sizes (e.g. Benson et al. 2014). Note that this concept is not without its detractors, including myself - I won't go into my reasons now but I plan to outline them here eventually.
Whether you agree with the bird-pterosaur competitive displacement hypothesis or not, we can't disagree that the end of the Cretaceous is almost entirely devoid of small pterosaur remains. Only a handful of specimens record small pterosaurs in the Campanian and Maastrichtian, and they're all tricky to work with. Aside from being highly fragmentary, some are controversially identified (such as Piksi barbarulna, an alleged small pterosaur from the Two Medicine Formation - see Agnolin and Varricho 2012 for the pro-pterosaur case) and others represent probable juvenile individuals (Godfrey and Currie 2005). Whatever it signifies, the lack of diminutive pterosaur specimens from the close of the Mesozoic is a real phenomenon of our fossil record, and any new specimen of a small, latest Cretaceous flying reptile has to be something to get excited about.
Enter: a new small, latest Cretaceous pterosaur specimen to get excited about
|Title slide of my SVPCA 2016 talk, discussing the findings of Martin-Silverstone et al. 2016, out today. If you don't get the reference, you clearly get out too much, have too many friends and aren't watching enough crap TV.|
|RBCM.EH.2009.019.0001, a fragmentary azhdarchoid pterosaur from the Campanian Northumberland Formation, British Columbia. It's, er, not the prettiest pterosaur specimen you'll ever see. Combination of figures from Martin-Silverstone et al. 2016.|
We've identified the Hornby specimen as an azhdarchoid, and noted several features indicative of, but not conclusive to, an azhdarchid ID. We suspect the specimen is an azhdarchid because of its provenance and its basic anatomical characteristics, but the specimen does not contain the right bits to confirm an azhdarchid identity. Nonetheless, narrowing the specimen down to Azhdarchoidea allows us to estimate its body proportions and confirm that the specimen was indeed a small animal when it died. We estimated its wingspan using two methods factoring both the humerus and vertebrae, and each pointed to a wingspan between 1.4 and 1.6 m. That puts our pterosaur at a comparable size to a good sized-seagull and, while these are respectably-sized modern birds, this is small for a latest Cretaceous pterosaur. Rather than poking giraffes in the face, our little chap would only just be beyond predation risk from an average housecat (below). The only contemporary pterosaur competing with the Hornby azhdarchoid for size is Piksi, a poorly known possible pterosaur from the western US. Our new study lists a number of reasons why the pterosaurian characterisation of Piksi is problematic however: in short, its morphology is all wrong for a flying reptile and we suspect a non-pterosaurian ID is more likely. The Hornby specimen is thus a contender for the smallest latest Cretaceous pterosaur currently known.
|A 1.5 m wingspan azhdarchoid next to one (SI) MrTiddlesmetre. From Martin-Silverstone et al. (2016).|
|What's inside the RBCM.EH.2009.019.0001 humerus? A mix of things, but among them are features indicative of late-stage juvenility/subadulthood. Please see the paper for details of this figure. From Martin-Silverstone et al. 2016.|
A small pterosaur amongst the pigeons
|...except when pterosaurs stole their eggs. Our PR art for the new paper, where a group of Hornby azhdarchoids perform guerrilla raids on shore-living Campanian bird nests. Take THAT, birds.|
With all this said, the most important message of the paper has to be this: we need more data on small pterosaurs in the latest Cretaceous. The specimens we have are scrappy, hard to work with and offer limited scope for analysis. Thus, any small Late Cretaceous pterosaur material is significant, and whether they're lying unnoticed in museum collections or pulled straight out of the field, they are noteworthy specimens which need to be put on record. Curators and researchers, please keep your eyes peeled!
And that, in a nutshell, is our new paper: be sure to check it out if you want more details. You can also read Liz's take on the study over at The Conversation and other experts have been chiming in at news sites covering the story. With a bit of luck, this is not the only news you'll be hearing about Late Cretaceous pterosaurs from these quarters this year - more on these projects as they move along. All that's left to do is to thank Liz and Victoria for inviting me to collaborate with them on the new specimen - I learned a huge amount trying to get my head around this challenging material and its histology, and had a blast working with them.
This blogpost, paper and artwork are sponsored by PatreonRegular readers will know that this blog and its art are sponsored by a suite of awesome Patrons, but this post is proof that this support goes further than mere internet tomfoolery and contributes to papers and outreach, too. Supporting my blog from $1 a month not only helps keep this blog ticking over, but helps me contribute thoughts, words and illustrations to scientific research. In return you get access to bonus blog content: additional commentary, in-progress sneak-previews of paintings, high-resolution artwork, and even free prints. For this post, we'll be talking about the PR art I've done for this research: how was the azhdarchoid reconstructed from that
|Two Garjainia madiba decide who gets the table scraps. The reconstructions here are modified from the life reconstruction I provided for Gower et al. (2014).|
Alas, erythrosuchids don't get as much love from palaeoartists or outreach projects as they deserve. Their marriage of a proportionally huge, sharp-toothed skull with a crocodile- or lizard-like body is unlike anything around today and it's difficult not to wonder how they functioned as living animals. Closer inspection of their anatomy reveals more sophistication than we might assume from the few illustrations of these animals available online or in books, and it seems that their role in Mesozoic ecosystems and reptile evolution was an important one. These were a successful, abundant group of predators with an evolutionary run spanning the Early and Middle Triassic (12 million years in total) and a near cosmopolitan distribution. Moreover, they remain important species for understanding the early evolution of archosaur-line reptiles. They really do have a lot going for them, but they just haven't quite caught public imagination.
A few years ago I was commissioned to reconstruct the small(ish), early erythrosuchid Garjania madiba for David Gower and his colleagues for their 2014 descriptive paper (below). The brief was for a straight illustration of the animal rather than a restored scene, and I promised the team I would put this reconstruction in a landscape one day. Two years later, I've finally got around to it: the results are above. Posting this painting seems like as good an excuse as any to lavish some much needed attention on these most encephalised of reptiles, so let's get stuck in.
|G. madiba reconstruction from Gower et al. (2014). Note prominent bosses on the face, a characteristic feature of this species.|
What, exactly, is a erythrosuchid?You can find erythrosuchids in Triassic rocks on every continent except North America and Antarctica and, although relatively complete specimens are not common, many species are represented by large inventories of bones. Despite this relative glut of material, the classification of erythrosuchids - from the fine anatomical characteristics of the group, to their position in the reptilian tree and the number of species contained in the clade - has been the subject of long-standing, ongoing discussions among palaeontologists. Older erythrosuchid literature is confused by a multitude of different classifications which entwine erythrosuchids with other large-headed, carnivorous archosauriforms such as raisuchians and proterosuchids. Researchers have long realised the problems with these schemes, but unpicking the relationships of these groups and other early archosaur-line reptiles has been tricky. With the arrival of extremely detailed and well sampled cladistic analyses of archosauromorphs (e.g. Nesbitt 2011; Ezcurra 2016) we might be moving towards greater consensus on the systematics of these animals, however. In modern schemes, erythrosuchids are recovered as non-archosaur archosauriforms close(ish) to the base of Archosauria. More specifically, they are the sister clade to the the Eucrocopoda, the large clade that contains the likes of Euparkeria and proterochampsids, as well as the true archosaurs(Ezcurra 2016).
|Erythrosuchus africanus skull, restored by Gower (2003). Note the extremely robust construction of the bones and expanded areas for neck muscle attachment.|
Although erythrosuchid skulls were almost certainly pneumatised in some areas, the largest opening in the skull is not, as we might expect in such large headed animals, anything to do with a pneumatic cavity. Rather, it's the lower temporal fenestra, an opening typically associated with allowing bulges of the jaw adductor muscles. This, as well as the presence of a small sagittal crest between the superior temporal openings (which overly the same muscle block) and the depth of the posterior mandible likely betrays the presence of massive adductor muscles in temporal region of the skull. Eryhtrosuchid skull bones certainly look sufficiently robust to withstand powerful biting, the bones forming the temporal fenestra, jaw and orbital margins being extremely massive and thick and tightly interlocking with complex sutures between each bone. Interestingly, Shansisuchus has the same partly invaded orbit shape that Henderson (2003) linked with reinforcement against heavy bite forces in theropod dinosaurs: perhaps similar buttressing was taking place in these Triassic reptiles
|The dorsal extent of the occipital face in Eryhtrosuchus africanus, posterior view. The rounded flanges at the top poke above the rest of the skull, and perhaps indicate expanded neck muscles in this and other species. From Gower (2003).|
Behind the skull we see a fairly typical Triassic archosauriform body (below). The neck is short, and especially so in some of the larger species, and the majority of the vertebrae are adorned with tall neural spines: these almost certainly provided anchorage for axial musculature related to supporting the head and back. The pectoral elements, which are also employed somewhat in neck musculature, are also robust. Their tails are moderately long, with deep chevrons in the anterior region likely related to hindlimb musculature. Behind these, the tail becomes rather slender. Gower (2001) proposed that Erythrosuchus vertebrae possessed pits and depressions possibly related to the development of post-cranial pneumaticity, the first found outside of pterosaurs and dinosaurs. This would be a significant find, telling us something of erythrosuchid lung structure as well as the early evolution of postcranial pneumaticity in archosaur-line reptiles. However, both O'Connor (2006) and Butler et al. (2012) argued against this interpretation, noting that the features in question were not associated with internal cavities, thus failing to meet criteria for structures of pneumatic origin. An important caveat to this, however, was raised by Butler et al. (2012): the phenomenon of pneumatic tissues invading vertebrae and other postcranial bones almost certainly did not evolve in one swoop. Its earliest stages may have simply been pneumatic tissues 'pushing' against external bone walls, forming pits and cavities, rather than invading them entirely. If so, the sort of thing Gower (2001) found in Erythrosuchus might be what we'd expect of early stage, postcranial pneumaticity. So while we have to concede that these structures do not meet our current definition of a postcranial pneumatic structure, perhaps we also need to learn more about the early evolution of postcranial pneumaticity before this hypothesis can be ruled out entirely.
|Mounted Garjainia prima skeleton as mounted at the Paleontological Institute, Moscow. Certain aspects of this skeleton are reconstructed or sculpted, so take some details with a pinch of salt. From Ivakhnenko and Kurochkin (2008).|
A point of contention among researchers is whether or not erythrosuchids had osteoderms. Two examples of such structures have been found in association with a specimen of Erythrosuchus, but they show no consistency in their morphology (Gower 2003). Moreover, the extensive inventory of Erythrosuchus and other erythrosuchids have yet to show additional evidence of dermal bones (Ezcurra et al. 2013). The safe bet, for the time being at least, is to assume these reptiles did not have osteoderms, and that those previously referred to the group were a fluke association from another animal.
The life and times of Triassic big-headsWe have much to learn about many aspects of erythrosuchid palaeobiology: details of their dietary preferences, locomotor mechanics and likely habitats remain only provisionally researched. Much of what we've learned about their lifestyles comes from 'bigger picture' assessments of Triassic diversity and faunal turnover, so we can only paint a broad-brush picture of their ecology at this time. That's not to say we have no specific palaeobiological insights into these animals, however. For instance, there is consistent histological evidence that erythrosuchids grew quickly, perhaps at rates comparable to pterosaurs and dinosaurs, until they reached reproductive maturity (de Ricqlès et al. 2008; Botha-Brink and Smith 2011; Ezcurra et al. 2013). Given that this trait is not limited to erythrosuchids among Early and Middle Triassic reptiles, this is one reason it's thought that archosaur-line reptiles may not be ancestrally ectothermic. Whatever the cause, rapid growth may have played some role in the success of erythrosuchids and other reptiles as ecosystems were rebuilt in the early Mesozoic (Sookias et al. 2012).
Erythrosuchid ecology remains only lightly investigated, but they have been considered arch terrestrial predators by some (Sennikov 1996 - see below). Interestingly, their size puts them among the largest terrestrial animals known from their respective faunas (Sookias et al. 2012). This is unusual: in post-Middle Triassic ecosystems we generally find herbivores are the largest animals in terrestrial ecosystems, so what's going on here? It's thought that physiological distinctions between large Early-Middle Triassic reptiles and the synapsid herbivores they coexisted with may explain the size difference (briefly summarised, archosauriform growth rates and respiratory anatomy may have permitted larger overall body size than therapsids - see Sookias et al. 2012), but how did this translate into ecological balance? Energy is lost as it is transferred between species in food webs, so how did populations of relatively 'giant' top-tier erythrosuchids sustain themselves on consistently smaller prey? Perhaps they were simply comparatively rare, or very energy-efficient, or maybe they supplemented their diet with non-terrestrial food items - did they also take food from aquatic realms, perhaps?
|An Early Triassic terrestrial food web, reconstructed for the Yarenga Formation by Sennikov (1996). In this scheme, most things ended up in the bellies of erythrosuchids or rausuchians.|
In recent years, however, erythrosuchids seem to have been perceived as more terrestrial animals (Sennikov 1996; Botha-Brink and Smith 2011; Ezcurra et al. 2013). Their thick bone walls are explained as being a consequence of their large size rather than aquatic habits (Botha-Brink and Smith 2011) and the deficit of obvious aquatic adaptations in their skeletons has been noted by several authors (Botha-Brink and Smith 2011; Ezcurra et al. 2013; Gower et al. 2014).
|Aquatic, semi-aquatic or fully terrestrial? This guy's meant to have taken a dip in the water, but was it intentional or accident? We may not have the data to say exactly what erythrosuchids did for a living yet.|
I love it when a bauplan comes togetherPerhaps one of the most interesting things mentioned recently about erythrosuchids is how little their postcrania differs from those of other archosauriforms, despite their substantial cranial modifications (Ezcurra 2016). This is something we see again and again in Triassic reptiles: relatively conservative bodies with highly localised outlandish anatomy, and is true even for the weirdest Triassic creatures. For example, Tanystropheus isn't that strange aside from its incredible neck, and (what we know of) the body of Sharovipteryxis not that atypical in spite of its leg-wings. I wonder if Triassic animals get the short shrift in popular circles because they're viewed as boring 'also rans' taxa which evolved strange, untenable anatomies but without moving too far from a typically 'reptilian' visage.
But perhaps what we're seeing with these animals is far more interesting than it first appears: a display of the intrinsic adaptability of the archosauromorph bauplan, and how applicable it was to many lifestyles with only localised modification. We can be particularly impressed with erythrosuchids because of their rapid evolution so early in the Triassic: they very quickly and successfully jumped into the niche of large, hypercarnivorous apex-predator after the end-Permian extinction event, and then held that niche worldwide for 12 million years. The fact they did so without much additional modification to the postcrania is evidence that their success was not a fluke, and that the basal archosaur-line body plan was a strong one. Perhaps instead of looking at erythrosuchids and other Triassic archosauromorphs as those strange, but ultimately dull animals that struck it lucky before the more successful ones took over, we might view them as some of the earliest evidence that the archosaur-line bauplan had real potential, and a sign of what was to come.
Big blog posts about big headed reptiles need big support - thank goodness for PatreonThe paintings and words featured here are sponsored by a group of tetrapods with more modestly proportioned skulls, my Patreon backers. Supporting my blog from $1 a month helps me produce researched and detailed articles with paintings to accompany them, and in return you get access to bonus blog content: additional commentary, in-progress sneak-previews of paintings, high-resolution artwork, and even free prints. For this post, we'll be looking at the history of the painting up top, documenting its long 2-year journey from illustration to, er, a more detailed illustration. I'll also share the bizarre, sausage piglet monster version of Garjainia that you were never meant to see. Sign up to Patreon to get access to this and the rest of my exclusive content!
|Bear-sized gorgonopsid Inostrancevia latifrons. Sabre-teeth? What sabre teeth?|
Many words – mostly published at blogs, online mailing lists and social media - have been typed to discuss the credibility of lipless palaeoart, but the subject has traditionally received only cursory attention from academics. Happily for artists, this is starting to change. A small set of literature exists which debates the presence of extra-oral tissues in dinosaurs (e.g. Ford 1997; Knoll 2008; Morhardt 2009; Keilor 2013; Reisz and Larson 2016), and most this agrees that some sort of soft-tissue - at least 'lips' - covered their teeth. However, a running theme of these works is that reliably inferring soft-tissues of the face is not a simple task, and we really need more data to be sure of anything. Work on more recent fossil mammals shows more reliable inferences (e.g. Wall 1980; Antón et al. 1998), obviously benefiting from soft-tissue data from a range of extant, close relatives. New insights on the evolution of mammal cranial nerves are helping to understand the development of sensitive lips and cheeks in stem-mammals (Benoit et al. 2016). It's still early days for understanding fossil facial tissues, but at least it feels like we're off the line.
Collectively, there seems to be recognition among the academics interested in this topic that understanding the tooth coverage of fossil animals lies largely in understanding living animals. Attempts to understand tooth exposure from skulls alone - through making inferences about tooth size, jaw closure and speculations on how extensive soft-tissues can be before they become untenable - do not consider all necessary data. For example, Prehistoric Times palaeoart adviser Tracy Ford (1997) looked solely at the skulls of predatory dinosaurs to infer the absence of lips, suggesting their teeth were so long that they would pierce lip sheathing once the jaws were closed. This study assumed that predatory dinosaurs closed their mouths to the extent that the teeth of the lower jaw contacted the roof of the mouth, and that the preserved tooth configuration was the condition in life. These points are common issues raised against lipped dinosaurs, but there are several major problems. Dissections and CT scans of reptile heads show that jaw muscles and other soft-tissues have a major influence on mouth closure, to the extent that reptile jaw skeletons are typically loosely closed under their skin, even when the mouth is fully sealed. Taphonomic studies show that teeth slip readily from their sockets after death and often fossilise in far more vampiric states than they were in life. And undermining this further is that no extant taxa with lipped jaws were used to calibrate a limit for oral soft-tissues. Arguments about tooth coverage based on simply looking at skulls, without detailed consideration of modern animals and their anatomy, border on being arguments from incredulity : "I don't believe the anatomy could do that."
Modern animals and their tooth coverageFor an upcoming project, I've been trying to crystallise my approach to restoring ancient animal facial tissues, and deciding whether to cover their teeth or not is an important part of that discussion. I've been deliberately broad in this assessment to attempt to try to sort the wood from the trees: discussions of oral tissues can sometimes get lost in the minutiae of tissue types, uncertain osteological correlates and so on - and many of these discussions result in the same answer: they can't be resolved with current data. That's not to say they aren't important discussions, but it's helpful to step back to see if we can answer the simpler questions as well: what gauge of teeth can be covered by oral tissues? When are teeth actually exposed? And what questions should we, as palaeoartists, be looking to answer when restoring facial tissues?
Reviewing literature and galleries of modern animals, we can see that overwhelming majority of living tetrapods have covered teeth, including all amphibians, most mammals and most reptiles (excluding birds, naturally. Hey, if they wanted to be involved they shouldn't have lost their teeth). Exposed teeth are actually really rare, and a character completely absent in many major clades. The soft-tissues involved in covering the teeth are variable, but 'lips'– either slightly fleshy margins of skin, or skin overlying true muscle - are so universal among tetrapods, as well as living relatives like lungfish, that we might assume lip tissues of some kind were ancestral to the group, and breaching these with large teeth is a derived condition evolved independently in a minority of lineages. Crocodylians are the only living tetrapods with fully exposed teeth, but it's increasingly obvious that they're also pretty specialised/derived/downright weird (Grigg and Kirshner 2015). Far from being 'living fossils' frozen in evolution, they have so many anatomical nuances and specialisations that their use as model organisms for other extinct taxa is increasingly questionable. This applies to aspects of their facial anatomy too - we’ll discuss this in more detail below.
We owe many of these surprises to animal lips, which are generally much more extensive than we casually assume. Large teeth can slide into soft-tissue sheaths located between gums and lips, and these are quite visible in the open mouths of some species. Amphibians, lizards and many mammals have upper and lower lips of similar size which meet over the teeth and sheaths can form on either jaw, but some mammals – including most carnivorous forms - have very large, fleshy upper lips over thinner, tightly-bound soft-tissues of the lower jaw (Antón et al. 1998). In these species, the canine teeth overbite the lower lip but the upper ‘over-lip’ is large enough to obscure the fact that the tooth is outside the lower mouth tissues. I am unaware of a reversed situation with the lower lip covering a thin upper lip: this may reflect the fact that overbiting dentition is much more common than underbiting. Regardless of the specific configuration, it is clear that we should not underestimate the capacity for facial tissues to obscure even very large, sharp and ferocious-looking teeth. The assumption that all conspicuous teeth of fossil animals were on display in life is thus problematic and does not agree with what we can observe in modern animals (below).
What's up with crocodylians?The elephants – or rather large semi-aquatic reptiles – in the room here are crocodylians: why do they have exposed teeth when all other tetrapods have largely covered mouths? Their teeth are not overly large, nor acutely angled. Some (Reisz and Larson 2016) have argued crocodylian dentition is only possible because of their semi-aquatic habits. The (unpublished, currently conference abstract only) Reisz and Larson hypothesis is that exposed teeth – specifically their enamel component – are at risk from desiccation and breakage without constant hydration from saliva or environmental water (Reisz et al. 2016). This is an interesting idea which potentially gives artists a useful, practical guide to restoring prehistoric animals: anything living outside water with enamel-covered teeth must have covered them with soft-tissue. Despite its unpublished status, this idea has already chimed with some quarters of the online palaeoart community who're restoring anything with enamel-covered teeth with full sheathing.
|Musk deer, Moschus, canines in lateral and medial view. Note the (white) enamel layer on the lateral surface, but dentine (grey) on the medial. From Hillson (2005 - the scale bar is likely erroneous!).|
Furthermore, there are important caveats about crocodylian facial tissues that we have to factor into any discussion of their lipless configuration. Crocodylian faces are far more specialised and unusual than they first appear, and this may factor into their lipless mouths. Their highly keratinous facial skin undergoes a developmental pathway unlike that of any other amniote (their facial skin is essentially have one, highly 'cracked' scale) (Milinkovitch et al. 2013) and their heads are riddled with hyper-sensitive Integumentary Sense Organs (ISOs). ISOs are another unique crocodylian feature and are attuned, among other things, to sensing tiny vibrations in water (Soares 2002, see Grigg and Kirshner 2015 for a recent overview). In at least some parts of the crocodylian skull ISOs are situated over tiny foramina, presumably housing nervous tissues, and the overlying epidermis is thinned, with a reduced keratin component, to enhance their sensitivity (Soares 2002). We can thus see that ISOs do have a role to play in configuring crocodylian skin, and they present many questions that palaeoartists should be interested in. Are ISOs an important reason for crocodylian faces having such tight, contour hugging and lipless skin? Do the major functional and developmental distinctions of croc faces explain the lack of crocodylian lips? It might explain why virtually no other aquatic tetrapods have abandoned lips - aside from the the odd (and perhaps only) exception like the South Asian river dolphin*, there are no whales, snakes, seals or otters with crocodylian-like, fully exposed teeth. And given that no other lineages have osteological correlates for ISOs, should we put huge caveats around using crocodylians as models for facial tissues in anything other than their own ancestors? I don't know if anyone has answers to these questions yet, but they're food for thought when using crocodylians as ammunition for lipless reconstructions of fossil animals.
*Thanks to Ádám Lakatos for pointing out the toothiness of some river dolphins!
It's still very early days for the enamel/oral covering hypothesis, but modern animals suggest that interpretations of enamel precluding extraoral teeth are definitely more complicated than they first appear, and may even be flawed. If so, the simple presence of enamel on the teeth of fossil organisms may not be as useful to artists as some are currently suggesting. But this conclusion is preliminary, and we need to wait for this idea to mature before it's shot down entirely. We know, for instance, that there's more than one type of enamel among vertebrates. Reptilian enamel, for instance, is both thinner and of different microstructure to mammalian enamel, and these clades have rather different approaches to tooth longevity. This may mean something for enamel desiccation and long-term tooth exposure, and we may think differently on this matter once this research has been completed.
Predicting tooth exposure in fossil species
|Fully 'lipped' gorgonopsids and theropods: maybe not be as exciting as their toothy variants, but are they more credible? Well... if modern animals are anything to go by, probably.|
If this is so, only especially long teeth which project a considerable distance from the margins of the skull and lower jaw should be considered strong candidates for permanent exposure. Select examples might include the canines of certain mammalian carnivores (e.g. Smilodon and other machairodont felids), the tusks of fossil elephants and their relatives, and the larger tusks of dicynodonts. We should also note those fossil reptiles – such as certain crocodyliformes, pterosaurs and marine reptiles – where entire toothrows are composed of dentition so long that their tips extend well beyond the margins of the jaw skeleton. Such extensive dental apparatus would seem to preclude the development of any sheathing tissues, at least akin to those exhibited by from modern animals, and these animals probably had fully exposed toothrows in life. Of course, this conflicts with the observation that food-processing teeth are almost always covered in the modern day. However, we can defend this approach by arguing that their morphology gives a strong reason for ignoring this guideline: it answers the "why we shouldn't give them lips?" question.
Dunae Nash's recent discussions about sheathing Smilodon: given that this rests heavily on enamel being a no-no in exposed teeth, I'm unconvinced for the reasons explored above.
The concluding caveatOf course, it must be reinforced that these are just guidelines - and guidelines based on my own qualitative studies, nonetheless, your mileage with them may vary - and there are exceptions to the suggestions made above. As is well known, for all the suggestion that restoring sabre-toothed cats with exposed teeth is reasonable, one living cat species – the clouded leopard – does cover a set of long upper canines in a lower lip sheath. We would not predict this based on other cat species and, if known only from fossils, clouded leopards would probably be restored with a slightly exposed canine. Likewise, the exposed tusks of some deer are not especially massive, and if we followed the suggestions above we'd probably cover them up in a reconstruction. But palaeoart is ultimately a game of prediction and probability, attempting to restore what is most likely to fill gaps in our data, and any game of odds will have some failures. That’s not to say we shouldn’t ignore these exceptional examples - they show that guidelines can't be trusted all the time - but it makes sense for us to know where the guidelines are in the first place. As with all aspects of palaeorestoration, all of us stand a chance to be proved wrong about our artistic decisions: if and when that happens, the best we can hope for is to have been wrong for the right reasons.
This blog post was covered by PatreonThe paintings and words featured here are sponsored by a group of animals which also have sheathed dentition, Patreon backers. Supporting my blog from $1 a month helps me produce researched and detailed articles with paintings to accompany them, and in return you get access to bonus blog content: additional commentary, in-progress sneak-previews of paintings, high-resolution artwork, and even free prints. Sign up to Patreon to get access to this and the rest of my exclusive content!
The best holiday of the year is just around the corner: Halloween! It's the season to celebrate the macabre, the weird, the dark and the terrifying. It's the best excuse to watch all your favourite horror movies. And it's the time to spend hours making costumes that you can't really see out of or eat or drink in, but that's OK because you're doing this for the art, not the practicality. Yes, it's Halloween: king of the holidays.
This year, an impending honeymoon and my attendance at Dinosaur Days 2016 (a palaeontology/palaeoart event being held at the WWT Wetland Centre, London, 28-29th October - it's going to be awesome, and you should come along) means I can't celebrate Halloween as normal. But dammit, I'm going to do something, even if that means just celebrating a little here by sharing some off-topic art.
Sometimes, very rarely, I take a break from painting and writing about palaeontology and turn my attention to vintage science fiction, producing paintings of some of my favourite stories, characters or monsters, and the creatures of H. P. Lovecraft are a frequent subject. With Halloween being just around the corner and Lovecraft's tales of sinister cults, strange creatures and other-worldly horrors being pretty note-perfect fodder for this time of year, I'm going to take the blog off-road with a short gallery of my Lovecraft paintings. Although we're going to be pretty palaeontology-lite for this post (folks here for coverage of extinct creatures may be pleased to know we'll be back to normal very soon) we're not abandoning the concepts of biology and evolution altogether. One of the things I find appealing about Lovecraft's work is the frequent nods to biology, geology and evolution, and creating biologically plausible(ish) versions of his creatures was a primary goal of the work shared here. We're not quite in the territory of full-on speculative evolution with this post, but I've tried to make my discussion at least a little informed. Right, enough preamble, let's get stuck in. (Oh, and a major SPOILER WARNING for those of you who haven't read Lovecraft's most famous stories and books.)
The InnsmouthiansFirst up is a take on some of my favourite Lovecraftian creations, the residents of the decrepit fishing town Innsmouth, as described in The Shadow Over Innsmouth. They're among the few Lovecraftian creatures which stand a chance of being depicted well in art because they're real, physical beings rather than elemental or transmaterial whosermerjiggers that are meant to drive people mad simply by violating the laws of physics.
|Deep Ones and their allies search Innsmouth for the narrator. The one in the middle seems to have forgotten what he was doing.|
The Deep Ones, the hybrid humans and their devious human counterparts are terrific, enigmatic villains and they feature in one of the most exciting of Lovecraft's stories. The Shadow Over Innsmouth is one of his few tales with a sustained action sequence, and it was this that forms the focus of the painting above where men and inhuman, bactracian beings pursue the narrator. I approached illustrating the Deep Ones using both Lovecraft's brief descriptions as well as keeping some basics tenets of biology in mind. In the novella, these creatures are described as sharing ancestry with humanity and retaining a capability to breed with us too, the resultant hybrid phenotype passing through a human stage before attaining Deep One characteristics. It's hard not to see this as a nightmarish variant on peramorphosis, the evolutionary process where growth is accelerated or extended to produce exaggerated features (it's the opposite of paedomorphosis, a more familiar evolutionary phenomenon where growth slows or ceases so that juvenile features are retained to adulthood).
I wanted to keep my Deep Ones fairly 'grounded', looking like beings that up until their latest growth stages passed for strange looking people, as well as sharing some of the basic tetrapodiness that we might expect of clade we have recent ancestry with. Thus, they still have anthropoid proportions and faces, with the exception of a certain tall froginess about the head, and a further exception being elongate hindlimbs to permit more effective swimming and bounding, as described in the novella. Their feet are also large to aid their swimming potential. I took inspiration from early tetrapods and tetrapodomorphs in removing some of the distinction between the head and shoulders and widening the oral tissues to create an amphibian-like mouth instead of a cheeked human face. The gills were kept relatively subtle, as they appear to be in Carboniferous tetrapods, rather than wacky fin-like structures that recall the designs of Ray Harryhausen. My hope is that creating a set of more grounded creatures rather than slimy-finny-tentacle-beings makes them a little creepier, too. My own responses to horror imagery are that distortions of real life are much scarier than all-out fantasy entities.
It also seemed important to show some of the creatures wearing clothes, something we rarely see in artwork of these creatures but mentioned several times in the story. I think this helps show that they are meant to be intelligent creatures on par with humans in terms of civilisation and culture, even if one of them - the bounding individual on the right - only wears a dirty, ill-fitting human shirt as a remnant of its former life (note the shirt is now incapable of buttoning properly around its fattened, gilled neck). The figure on the left wears a tiara and robes, another nod to specific references in the story and suggesting some sophistication in this species. A few normal-looking people are in the scene too, nodding to the fact that the whole town is associated one way or another with Innsmouth's peculiar goings-on. I think this is why the Innsmouthians are great villains: even those who aren't tainted with 'the Innsmouth look' are in on the game, and those who have lost their humanity remain man-like abilities, intelligence and malevolence. At the heart of The Shadow over Innsmouth is a story about how corrupt and nasty real people can be when they have things to hide.
Dagon: benthic whale wrestlerMoving on, the next image shows another famous Lovecraft creature, one we've come to know as Dagon, from the story of the same name. How Dagon fits into the rest of the Lovecraft universe is a bit murky. Some do not count it as part of the Cthulhu Mythos (indeed, Call of Cthulhu can be seen as a elaborate, Mythos 'canon' retread of Dagon) and the creature in Dagon is never explicitly identified as 'Dagon' itself. We assume it is the titular beast because of its prominence and because several aspects of its nature correspond with the popular, if erroneous, fish-god interpretation of the near-eastern deity also known as Dagon, but confirmation of this is not provided in the story. But something known as Dagon is continually referred to throughout other Lovecraft stories however, and we might assume that - as with his other in-universe references - these are nods to the creatures and scenarios outlined in his earlier work. My work and discussion here assumes that all references to 'Dagon' in Lovecraft's work point to the same entity, including all references to beastly creatures in the Dagon tale itself.
|Dagon, imagined as a giant, facultatively-bipedal, whale-murdering member of the benthos, here taking a trip over land to visit his favourite monolith.|
With a human-like bauplan not being terrific for swimming, I assumed Dagon is a member of benthic communities and gave it large, weight-dispersing feet and hands to facilitate walking on soft marine oozes at the bottom of the sea. It's meant to be a facultative biped, something which can locomote like a man if needed but probably spends more time moving like a gorilla. Its limb girdles and musculature are small and on account of it being a bulky creature mostly living in and supported by water, and we could see this being a sluggish being on land. I don't recall any references to Dagon being a particularly intelligent creature in Lovecraft lore, and think this design conveys a slightly more animalistic, rather than humanistic, creature than the Deep Ones illustrated above. I quite like the idea that this thing may be a figure of worship for the Deep Ones not because its wise or divine, but simply because it's a giant monster that they fear. Sort of the Lovecraft equivalent of King Kong, I suppose. Now that's a movie I'd pay to see.
Echinoid Men from Beyond the Moon!
|Echinoid Men from Beyond the SpaceMoon. Is that the best caption I've ever written?|
Yes. Yes it is.
Painting the Elder Things was challenging because it is a little tricky to make them look, well, sensible and viable. I think this is partly because their appearance - based though it seems to be on living species - is pretty out there and grinds against creature designs that we're more familiar with. I mean, how many illustrations or movies show creatures that look the same from five different angles? I've done my best to honour Lovecraft's description here, the only omission from his overview being the absence of wings. However, these are mentioned as being retractable in the novel and thus consistent with all large flying animals to have ever evolved on Earth: wings, frankly, get in the way unless you're flying, so it makes sense for them to be stowed away until needed. Thus, although you can't see them in this illustration, the wings were considered and would be hidden between the bulges of the test (this also solves the problem of how to draw an animal with five wings). The bioluminescence is an exercise of artistic license as it is not mentioned in the novel, but I figure it adds both a sense of sophistication and eeriness to these figures. It's also in keeping with Lovecraft's echinoderm sources, several species of this clade having developed bioluminescent body parts. More by accident than design, the patterning created by the bioluminescent channels reminds me of body painting and masks of some human tribes, which seems appropriate for a race of super intelligent beings... even overgrown echinoids.
And finally...OK, we're just about done scratching this Halloween itch scratched for this year - I hope you've enjoyed it, or at least tolerated my indulgence. If this sort of thing is appealing let me know in the comments below and I'll consider posting similar post in future. I'm also making these images available as prints at my website shop should you want some Eldritch horrors for your own home. But enough seasonal fun: back to dinosaurs next time!
Except for one more thing... how could we have a Lovecraft Halloween special without a picture of Cthulhu?
|"In his house at R'lyeh, dead Cthulhu waits dreaming. And singing '100 bottles of beer on the wall'. He loves that song."|
Folks interested in the development of this picture, including a previous version, should check out this post at Matt Wedel's (yes, he of SV:POW! fame) blog Echo Station 5-7.
This blog (but not this post) is haunted by PatreonThe paintings and words that make up my blog posts are sponsored by a group of sentient, intelligent, non-echinoderm beings: my Patreon backers. Supporting my blog from $1 a month helps me produce researched and detailed articles with paintings to accompany them, and in return you get access to bonus blog content: additional commentary, in-progress sneak-previews of paintings, high-resolution artwork, and even free prints. There's no bonus content or charge for this post because it's so far off my normal topics and not what people have signed up for, but, all the same, sign up to Patreon to get access to past and future exclusive content!
Palaeoartistry is not a science. Even a conservative reconstruction requires artists to stretch data and evidence further than would be allowed for any scientific study and the whole process relies more on inference and speculation than many of us would like to admit. Yes, palaeoart is data-led and evidence-based, but only in rare circumstances do we have enough data to bring us to a single, reliable interpretation of a fossil species. Most of us would agree that there are some aspects of reconstructions that we can and should be getting 'right' for many species - basic proportions and musculature being top of the list - but beyond these science can often only narrow our choices, not present definitive answers. In lieu of clear scientific guidance, what guides these decisions may be our personal preferences, logical thinking, the demands of a project, or the penchants of our consultants. This means that, odd as it may seem, vastly contrasting reconstructions can be construed equally credible. A weird, alternative take on a fossil species might be just as ‘accurate’ to our knowledge as another preferred or familiar one. When evidence is equivocal for two or more states, we have to concede that one interpretation can be just as 'correct' as another.
With this in mind, I thought it might be pertinent to talk about the above reworked reconstruction of Plateosaurus engelhardti with a filamentous coat, and why – at time of writing at least - it’s perhaps neither ‘right’ or ‘wrong’ to depict this animal in this way. I could have covered it with scales as an alternative and not necessarily been ‘correct’ or ‘incorrect’, either. The question of whether sauropodomorphs were wholly scaly has not escaped discussion in many quarters - it was even mentioned at this blog briefly back in 2013 - so, for a change, and perhaps to mirror the sometimes antagonistic way that similar matters are discussed on social media, I’m going to present my thoughts here as a conversational debate between… myself. The idea is that it will allow for fuller discussion of opposing points, but I suspect it really just reflects the amount of time I spend alone at home with no-one but some chickens and various squamates for company. Whatever, hopefully the 'conversation' below will be balanced: both ‘pro-filaments’ and ‘pro-scales’ have important points to make, and I’m not strongly advocating one or the other here: the point is that both sides have valid points to make, so warrant an equal platform. Over to, er… me, then.
Me¹, meet Me²Me¹ (filaments, opening statement). Should we restore Plateosaurus and other sauropodomorphs with filaments? Maybe. The evolution of dinosaur integument is an increasingly complicated area of study, and the idea that scales alone were the most likely ancestral condition for the major dinosaur lineages is no longer certain. As is well known to many, in the last decade we’re discovered filaments occurring in not only theropods but also in disparate parts Ornithischia too, and detailed new studies are suggesting that filaments in the likes of Psittacosaurus are structurally similar to those of other ornithischians as well as extant and extinct theropods (Mayr et al. 2016). They may even be similar enough to suggest true homology (Mayr et al. 2016), which strongly implies dinosaur skin may have been at least partly fuzzy in its ancestral form. Indeed, with pterosaurs thrown into the mix as well, an ancestrally-filamentous Ornithodira remains not only a valid hypothesis, but one that has passed several important tests in recent years. This being so, a filamented Triassic sauropodomorph is a sensible extrapolation of modern data.
Me² (scales, opening statement). Should we restore Plateosaurus and other sauropodomorphs with filaments? Maybe not. Firstly, studies have shown that our reconstructions of the ancestral ornithodiran integument type remains highly sensitive to the condition of its basalmost species, and we lack fossil data on these forms (Barrett et al. 2015). The 'ancestrally filamentous hypothesis' is enjoying some invigoration from new discoveries and research, but the game is not over yet. Virtually all of our dinosaur skin samples stem from derived species that had plenty of time to modify their integument from the primitive condition, and we have to concede that - whatever we think about the ancestry of dinosaur skin - they were very plastic in integument types. Thus, an important test of this hypothesis will be the recovery of good fossil skin samples from Triassic dinosauromorphs and pterosaurs, and their close relatives. Until we find these, or a fuzzy sauropod fossil, the recovery of scales from all three major dinosaur clades means the argument for 'ancestrally scaled' remains valid.
Me¹. Three points in response here. Firstly, admittedly playing Devil’s Advocate, a <10% chance of sauropodomorphs being filamented is still a chance, right? A filamentous Plateosaurus may not show what is most probable, but it still shows something that science shows is ‘possible’.
Secondly, and more constructively, the fact that skin impressions are not known outside of true sauropods means we may want to question what that the sauropodomorph stats of the Barrett et al. (2015) study really tell us. Does it reflect the condition for all sauropodomorphs, or just Sauropoda? The same probability assessments gives a 50% chance of filaments being ancestral to Saurischia, so the the first sauropodomorphs must have a somewhat higher chance of being filamentous, or at least being closely related to filamented species. Presumably, that 50% chance of filaments doesn’t just plummet the moment we steer evolution to the sauropod line: it’s a long evolutionary road from a basal saurischian to the sorts of sauropods we have with skin impressions, and we have no idea if or when filaments were abandoned on that road. We have a data vacuum of skin at the base of Saurischia: after sauropods, the next closest saurischian with skin impressions to Plateosaurus is the abelisaurid theropod Carnotaurus - hardly a close relative at all. Our absence of skin impressions around the phylogenetic neighbourhood of Plateosaurus, and our data about the likelihood of filaments in saurischians as a whole favours open-mindedness about the life appearance of these animals.
The third point is that if recent claims about dinosaur filament homology are correct, we have to assume that these structures were present in some form in the stock that gave rise to all major clades. Seeing as theropods retained filaments after the theropod/sauropodomorph split at the base of Saurischia, we should probably assume that sauropodomorphs lost their filaments after that divide. If so, a fuzzy Triassic sauropodomorph is not a far stretch.
Me². But - even assuming homology of filaments - if Carnotaurus is scaly, and so are sauropods, we can contrarily hypothesise that saurischians were secondarily-scaly ancestrally. This might even be the most objective reading of the data we have.
Me¹. Perhaps, but is the data supporting that interpretation really reliable? Carnotaurus is actually a weird outlier among theropods, it being the only theropod known with extensively scaly skin impressions. We have to wonder how significant this is against the wider backdrop of extensively filamented coelurosaurs sitting just a little higher up the theropod tree. As the rootward-bracket of the theropod integument bracket it's almost irritatingly important - it has a lot of sway in our reading of dinosaur integument evolution - but we still have to view it as a single outlier against the wider picture of theropod integument. As with any outlier, we have to be cautious about over-interpretation, or thinking one datum can give us the whole picture. As with so many palaeontological issues, we need more information.
Me¹. The flip side of this is that ornithodiran integument has been proved complicated and surprising often enough that assuming variation in the poorly known areas is justified. Who expected Kulindadromeus and Psittacosaurus, or Tianyulong? Who, for that matter, would have predicted the first fluffy pterosaur fossils among - at that point - entirely scaly relatives? The point about exploiting unknown data is an important one, but we have a strong precedent for filaments in poorly sampled areas of ornithodiran evolution now. This is less exploiting a loophole than admitting we don’t have a full picture yet, and simply portraying one of the two more likely options of integument form.
Furthermore, Kulindadromeus and Psittacosaurus are great examples of how dangerous our approach to integument reconstruction is when we only have scraps of soft-tissue. It’s only because of their extensive soft-tissue preservation that we know they mixed scales and filaments in different body regions. And it’s not just these dinosaurs that show us that. Pterosaurs have scaly feet to counter their fluffy bodies (Frey et al. 2003), and the extinct mammal Spinolestes is known to have had scales, bristles, and variably long and short fur (Martin et al. 2015). Andrea Cau has even cast doubt on our presumed reasonable knowledge of Carnotaurus skin, pointing out that its skin impressions all pertain to the underside of the animal and that the dorsal surface could be entirely different. We thus have to ask what we really know about sauropod skin: are the bits we have representative of whole animals, or the group as a whole? The most extensive set we have - those from a diplodocid that might be Kaatedocus, described by Czerkas (1992) - show a lot scaling on the body, which meets the predictions we’ve made from smaller pieces of skin found with other sauropods. But it might be naive to think this offers a significant insight into these species, or rules out the chance of localised filaments on some sauropodomorph species.
Me². But where do we draw the line here? There has to be a point where we can say ‘we haven't seen evidence of filaments yet, and we should factor this into our science’ without someone going ‘you don’t know the whole animal yet!’. Some artists take this to an extreme, restoring animals like Edmontosaurus with large filamented regions despite this species being known from several well-studied and extensively-scaled mummified individuals. These have no evidence of filaments whatsoever, despite preserving scales down to millimetre resolution, and yet some folks are still unconvinced, speculating that filaments were poking through gaps between scales and so on. Palaeoart like this Plateosaurus reconstruction almost holds palaeontology to a standard of knowledge that it’s unlikely to ever attain: no, we don’t have skin impressions from every species, we don’t have good skin impressions from many species at all and fossils are never perfect records of animal appearance. But we have to use what we have: science does not work on a philosophy of 'assume whatever until proven otherwise'.
Me². It must be said that it would be easy to construct this conversation around a scaled version of this animal, and discuss why it doesn’t have filaments. Our base expectation for dinosaur integument and life appearance is in a state of flux, no matter what we personally prefer or assume.
Me¹. I think a point often lost on viewers of palaeoart is that these artworks are not, and cannot, be definitive, incontrovertible renditions of these animals. There are some animals so well represented in fossils that they lend themselves well to ultra-detailed reconstructions which are hard to quibble over to significant degrees - the awesome Bob Nicholls Psittacosaurus model being a great example (Vinther et al. 2016) - but for lesser known animals like Plateosaurus we are only painting hypotheses, not fact-based reality. This painting is one possible reconstruction of Plateosaurus as known in 2016, a time when interpretations of dinosaur skin evolution remain in flux. Time will tell if it's the product of over-interpretation of fossil data, or a lucky gambit later borne out with fossil evidence. I don’t mind getting stuff like this wrong: I’m more interested in painting and exploring credible possibilities of what we know now, not being ‘right’. We may never know what is ‘right’, so there’s not much point worrying about it. There are a couple of essays on this topic in my new book,Recreating an Age of Reptiles (Witton 2016).
Me². You’ve seen RecARep? I hear it’s awesome and that everyone should buy a copy.
Me¹. Wow, that’s desperate. Any actual final points?
Me². In a previous post on the role of pterosaurs in interpreting dinosaur filaments I concluded that: “Forcibly arguing for either scales or filaments at the base of Dinosauria seems premature at this stage, and, whatever our personal hunches are, it seems sensible to accept some ambiguity in this situation for now.” I think that’s true here too. There are certainly arguments to be had on both sides, some stronger than others, but neither side has knock-out data or evidence on the table yet. It’s the same old frustrating cop-out, but we need more fossils, and fossils of the right sort, to resolve this. Specifically, we need early saurischians or dinosauromorphs with good skin preservation, as well as that Triassic sauropodomorph with excellent skin remains. It must be said that these animals are not generally found in fossil Lagerstätten conducive to good soft-tissue preservation, so I’m not advising anyone to hold their breath for this one. But new techniques for detecting soft-tissues and increasing awareness of soft-tissue preservation in lithologies once thought to only preserve bone are reasons to be optimistic that we'll have insight on these matters one day.
Me¹. And ‘frustrating’ is the right word here, too. It seems like dinosaur science has made sufficient headway on understanding integument evolution and predictive methodologies that a reasonable, if provisional answer to the ancestral integument of the three major clades is close. But the puzzle piece needed to get our first good look at the broad picture is still out of reach.
|Awkward facial expression, bad fashion sense and a hygiene problem. No wonder no-one likes to paint early sauropodomorphs.|
Me¹. Pfft... Good… bad… I’m the guy with the graphics tablet.
Me². Movie quotes in scientific blog post don’t make you look clever, you know. You just cheapen the whole act.
Me¹. There is no fate but what we make for ourselves.
Me². What...? that doesn’t even fit our context.
Me¹. It wasn’t the airplanes. It was beauty killed the beast.
Me². Sigh, why do I hang around with you? I think we're done here.
So long everyone - I'm away from my computer for the next few weeks so I'm going to be pretty quiet in blog comments, social media and so on. Things will pick up again come December when we'll be addressing the sauropods in the palaeo-outreach room: has the popularity of dinosaurs above other fossil animals become a problem?
This blog post was inarguably supported by PatreonThe paintings and words featured here are sponsored by an excellent group of animals with regional variation in integument, Patreon backers. Supporting my blog from $1 a month helps me produce researched and detailed articles with paintings to accompany them, and in return you get access to bonus blog content: additional commentary, in-progress sneak-previews of paintings, high-resolution artwork, and even free prints. Later this month (much later - around the 28th/29th) I'll be uploading a video version of the presentation I gave over the Halloween weekend at Dinosaur Days 2016, entitled Palaeoart and the Never-Ending Quest for Accuracy. Here's the title slide to whet your appetite:
|"Oh, I see you're putting movie easter eggs in this post now too. This is why no professional blogging platform will pick you up."|
|Whether it's a giant armoured thyreophoran like Panoplosaurus mirus (thanks to the Empress of Ankylosauria, Victoria Arbour, for advice on this restoration) or a svelte theropod like Chirostenotes pergracilis, everyone likes dinosaurs and we - palaeontologists - like using them in our outreach. But are dinosaurs really universally popular and appropriate for the wide range of outreach we use them in?|
The success of dinosaurs in outreachExactly why dinosaurs occupy such an important and influential space in popular culture remains largely mysterious. On paper, dinosaurs are a group of extinct reptiles which are not - superficially at least - so different from other long-dead sauropsids, and yet they have somehow gained global fame and many dedicated followers. My suspicion is that dinosaurs uniquely combine obviously amazing, ‘high impact’ anatomy - large size, fantastic skeletal structures such as horns, huge teeth and so on - with bauplans that are easily understood by the general public, without being so familiar that they’re pedestrian. For instance, everyone can appreciate Allosaurus as an active, large bodied predator even if just looking at its skeleton in a museum, but - as bird-like as it is in detail - the overall form is somewhat alien and intriguing. Other fossil groups, such as ancient carnivorans or whales, are impressive enough but perhaps also too familiar to inspire our imaginations in the same way. At the other end of the spectrum are extinct creatures which are just too unusual for widespread appreciation. Perhaps their anatomy is too strange or their life histories are too obscure and difficult to relate to familiar biology. This applies to many extinct invertebrates, as well as several types of weirder vertebrates. Dinosaur biology is thus near perfect for outreach material: they’re visually impressive, anatomically and biologically accessible, but different enough to warrant interest. Whether this is the actual basis for dinosaurian appeal or not, museum staff, educators and merchandisers have realised for over 150 years that dinosaurs are an excellent way to interest the public and make money, and given them prominent roles in outreach. Aiding any intuitive draw we have to dinosaurs is a lot of social inertia, and part of the enduring appeal of dinosaurs is a long history of ingraining them into popular culture.
For those of us interested in science education, dinosaurs are one of the most important and potent tools at our disposal. We see them as not only fascinating subjects in their own right but as a way to introduce ‘bigger picture’, perhaps fundamentally more important, scientific concepts to lay audiences. Dinosaurs are gateways to discussions of evolution, adaptation, anatomy, biological diversity, extinction, geological time and the changing nature of the planet. They provide, as charismatic and fantastic creatures, perfect characters to maintain interest in discussions of these sometimes complex concepts, and well-known Mesozoic dramas - the breakup of Pangea, formation of the Deccan Trapps, the Chicxulub Impact - offer rich backgrounds to stage our conversations. Dinosaurs are more than just awesome animals: they’re public ambassadors for science, facts and intelligent thinking.
We cannot ignore the economic value of dinosaurs, too - and not just to Hollywood movie makers and toy manufacturers. Dinosaurs provide academia and its satellite industries with vital income because of their easy marketability and merchandising potential. Public interest in dinosaur news, books and artwork keeps authors and palaeoartists in work, while the pull of dinosaur exhibitions in natural history museums not only keeps turnstiles spinning but brings essential revenue - in the form of gift shop purchases, entry fees and cafe visits - to these underfunded venues. I don’t know that anyone has ever attempted to work out the net worth of dinosaurs to education, but, globally, their appeal must bring millions of pounds into venues that perform outreach every year.
Too much of a good thing?So hurrah for dinosaurs, then, and their role as not only fascinating subjects for research and art, but as bankable, relatable and demanded elements of modern culture. But the popularity of dinosaurs does have an impact on other aspects of palaeontological PR, and in some conversations at our workshop ‘dinosaur’ almost became a bit of dirty word. No-one will deny the positive aspects of dinosaur popularity, but their dominance in popularised palaeontology influences outreach strategies, merchandising and public expectation, and not always in a positive way.
Some of the problems caused by dinosaurs were outlined in detail during talks at our workshop. We heard that a large portion of natural history museum visitors are exclusively concerned with seeing dinosaur exhibits, challenging natural history museums to use the rest of their collections in a meaningful, impactful manner. This is despite many museum goers being unable to distinguish dinosaur remains from those of other animals without the aid of helpful signage. It seems that, for some museum visitors, dinosaurs act like a brand label, or justification for interest, rather than an excuse to visit a museum for a rounded educational experience.
We also heard that bringing attention to non-dinosaur groups can be extremely difficult, and the less dinosaur-like they are, the harder it is. Groups like pre-Cenozoic synapsids, extinct invertebrates, fossil fish and so on struggle for attention and require highly creative outreach tactics to receive any interest. One of the commonest strategies - used frequently for semi-technical books on fossil animals (below) - is to make sure dinosaurs remain prominently mentioned even in those events or products which are focused on completely unrelated groups of animals. We just don’t trust most non-dinosaur clades to draw crowds or revenue on their own and have to spin them as being relevant to dinosaurs in some way. Tellingly, the only groups to escape frequent dinosaur namechecking are those which are already somewhat ‘dinosaur-like’. Giant fossil mammals, pterosaurs and Mesozoic marine reptiles share aspects of size and gross appearance with Mesozoic dinosaurs and might be seen as ‘honorary dinosaurs’ by the public, and perhaps mistakenly interpreted as the genuine article by many. Both dinosaur-targeted museum visits and our resistance to promote palaeontological topics without a dinosaurian safety net questions whether dinosaurs are a genuine ‘gateway’ to wider scientific education, and perhaps suggests a rather narrower interest in prehistoric life among the public.
|Just some of the non-dinosaurian textbooks coming your way in 2017. Probably.|
The general expectation that dinosaur-related events or products skew towards children presents a complex set of challenges. Firstly, it can lead to older audiences deciding a priori that they cannot take anything away from dinosaur outreach because the event - whatever it is - is ‘just for kids’. I’m sure many of us have seen how ‘switched off’ parents of young dinosaur fanatics are when visiting outreach events, even though the people their children are speaking to may be expert scientists, experienced fossil hunters or world-renowned palaeoartists. Secondly, mismatched expectations of outreach events can be frustrating for both outreachers and audiences: attendees may wonder why a dinosaur event is pitched above the level of their children, while outreachers may feel over-prepared or over-invested in their activity programme when confronted with only young audiences. Perhaps the most concerning issue is that many outreachers and merchandisers use young demographics as an excuse for low scientific standards and sensationalism, promoting outdated, erroneous and sometimes idiosyncratic views of palaeontology because their audience is too young and insufficiently educated to know otherwise, or ignoring scientific data where it might curb child appeal. I am sure most readers can think of numerous examples of products - many labelled as ‘educational’ - which show evidence of this, and it’s easy to see how this attitude may play a major role in perpetuating outdated and erroneous ideas about the past.
One of our final discussion touched on perhaps another issue faced by dinosaur outreach: the schism between public and palaeontological appreciation of what dinosaurs are. For palaeontologists, dinosaurs are a constantly - and sometimes rapidly - evolving set of hypotheses and ideas, and this is what we generally try to present to the world in our outreach. But certain dinosaur concepts outgrew palaeontologist-steered media long ago and now occupy their own place in popular culture, one almost entirely divorced from developments of dinosaur science and instead orbiting their portrayals in film, TV and popular literature. Most of these products - even those produced in the last few years - stick to now long-outdated 20th century interpretations of dinosaur biology and, divorced from guiding hands of scientists, solely emphasise marketable aspects such as their size, perceived ferociousness, and unusual anatomy. The result is a public largely familiar with dinosaurs in a scientifically-distanced, simplified and monstrous form rather than the animals reconstructed through biological and geological sciences, and with little appreciation for their evolutionary context, the scientific techniques used to understand them, or their relationship to wider, ‘core themes’ of scientific outreach. Recent studies partly vindicate this view in showing that the public are generally unaware of even the most basic aspects of dinosaur science, such as the near 50-year old revision from the classic ‘tail-dragging’ posture to an elevated tail and horizontal body attitude (Ross et al. 2013). This is despite museums, artwork, documentaries and some of the most successful blockbuster movies of all time showing the latter since at least the 1990s. This being the case (and with an added caveat that the study in question was relatively small), perhaps our issue with dinosaur education is more severe than we thought: are people really engaging with dinosaur media at all, or are our subjects of research, artwork, and hallowed gateways to other sciences little more than time-fillers and distractions?
|Despite the best efforts of many scientists, the public at large seem to associate dinosaurs with considerably outdated interpretations and monstrous creatures. Reviewing recent successful entries into one of the most widely-accessed sources of popular dinosaur culture - Hollywood movies - is this surprising? Perhaps the most visually progressive rendering in this set are the sparsely feathered dromaeosaurs from Pixar’s The Good Dinosaur (bottom right). However, the state of their integument still recalls dinosaur palaeoart from the mid-1990s, and not the extensive feather body covering shown by fossil evidence and now commonly restored over certain dinosaur species. Image sources, from top row down; King Kong (2005); Godzilla (2014); Transformers: Age of Extinction (2014); Toy Story (1996 - onwards); Jurassic World (2015); The Good Dinosaur (2015).|
So, are dinosaurs as useful as we think for outreach purposes?The points raise a simple but significant question: how effective is dinosaur-based outreach, really? As noted above, many decisions about outreach are shaped around dinosaur science and resources are poured into promoting dinosaur science itself. But are we right to regard dinosaur outreach as highly as we do?
Trying to balance the positive and negative points raised above, my take is yes, dinosaurs are an effective means to bringing science to people… but probably only certain people. Specifically, they seem to work very well among those who are already tuned into palaeontology, natural history and general science, an audience composed mostly of adult enthusiasts and children. Beyond this, their effect seems to tail off quickly and they may actually be a barrier to effective outreach. Audiences with preconceived expectations of dinosaur-themed content may ignore anything dinosaur related, which is a concern with us giving dinosaurs such privileged consideration in educational material. Are we limiting our promotion of other topics that could engage these uninterested people? And is one of our challenges of popularising palaeontology making dinosaurs and related topics universally attractive, and not just subjects with appeal to specialist audiences or younger people?
Of course, your opinion on this matter may differ. But even so, I think most of us would agree that our wider education about dinosaurs and related matters could be more effective, or at least more nuanced and reflective of more topics, than it currently is. I am optimistic that a groundswell of suitable movements towards this goal may already be underway. Many modern curators, scientists and artists are attuned to matters of science communication and interested in identifying outreach issues, sharing best practise, evolving public engagement methods and reaching new audiences with new topics. The fact that this article is being written as output from a workshop dedicated to popularised palaeontology is evidence of these practises actually occurring, and it feels like the right questions are being discussed. How can we, and when should we, shift focus from dinosaurs? How do we make other forms of life/parts of museum collections of wider interest? How do we more effectively impart new science to publishers, movie makers and other non-educational bodies making palaeontologically-themed media? It’s also pleasing to see more discussions about the once largely backgrounded industry practises of palaeoartistry in both scientific and popular media. Realising the important role that palaeoart has for communicating science, many involved in its production are vocally distancing themselves from the ‘popularised’ image of dinosaurs to more nuanced, scientifically-validated and interesting portrayals of dinosaurs, as well as other forms of prehistoric life. We are still on the uphill part of this journey to revising our outreach approach, but it’s reassuring to know that a body of professionals are looking critically at dinosaur outreach and its wider impact.
|Minor victories in recent palaeontological outreach involve effectively communicating to certain, interested audiences that Deep Time was not a dinosaur theme park, and that fossil creatures did not spend all their time battling and roaring at one another. Evidence that this message has hit home with at least some audiences is reflected in the broadening depth and nuance of palaeoart being posted across the internet. Shown here: my take on Jurassic stem-mammals, a gorgonopsian, gliding drepanosaurs, a goniopholidid crocodyliform, Cretaceous albanerpetontid, erythrosuchids, and... Longisquama, whatever the heck that is. Not shown here: dinosaurs in premier view, or roaring. The challenge is getting scenes like this, and subjects like this, to wider audiences.|
The risk of failure is what prevents many of us, and our employers, from straying too far from tried and tested means of outreach. And yes, if we’re talking paleontology with the public, dinosaurs are an obvious safety net. But we should take advantage of the fact that we’re more enabled than any previous generation of educators to cooperate, create and promote the subjects we feel are important with only a little inventive thinking and technological knowhow. Individuals can now develop significant outreach resources without the need for expensive designers and developers; online promotion can be essentially free; and the increasing accessibility of printing - both 2D and 3D materials - is lowering the financial risks tied into ‘real world’ outreach events. Any public enterprise involves a level of investment and risk, but resourceful thinking and shouldering the brunt of development ourselves can minimise these.
In closing, I want to stress that I’m not wailing on dinosaurs. As may be evident from my own output, I think they’re fantastically interesting animals with an important role to play in outreach. But for dinosaur outreach to be successful and support, not restrict, other outreach efforts we have to realise their limitations, as well as their strengths, as public ambassadors.
This piece of outreach was supported by PatreonThe paintings and words featured here are sponsored by folks who are certainly very popular in my house, my Patreon backers. Supporting my blog from $1 a month helps me produce researched and detailed articles with paintings to accompany them, and in return you get access to bonus blog content: additional commentary, in-progress sneak-previews of paintings, high-resolution artwork, and even free prints. For this post we'll be looking at my new angry nodosaur painting, discussing ankylosaurs in palaeoart and why they're so darned challenging to render well. Sign up to Patreon to be part of the discussion!
|In an ideal world, all blog posts would start with images like this one. (Edited talk title slide I used back at SVPCA 2013 - we've been working on the project discussed below for a while now.)|
A quick primer for those of you who aren't familiar with Hatzegopteryx. The first fossils of this Romanian, Maastrichtian pterosaur were announced in 1991 but, on account of their considerable size and robustness, they were interpreted as belonging to a large theropod, not a pterosaur. Eric Buffetaut and colleagues reassessed these bones some years later and made their azhdarchid pterosaur identity apparent (Buffetaut et al. 2002, 2003). As with all giant azhdarchids, only scraps of Hatzegopteryx are known. Bits of skull and a broken humerus from the Densuș Ciula Formation form the holotype, and a large femoral shaft from the same formation may belong to this animal as well. All these elements are remarkable for their size - wingspan estimates of 10-12 m seem sensible (Buffetaut et al. 2003; Witton and Habib 2010) - as well as an unusual degree of internal reinforcement. In addition to thick bone walls (4-6 mm, which doesn't seem much, but is impressive for a pterodactyloid pterosaur), both Haztegopteryx humeral and jaw elements possess large amounts of coarse spongiose bone. This reinforcement may be related to the evolution of some very substantial anatomy. Buffetaut et al. (2003) were able to make a compelling case for a 50 cm wide jaw for this animal, and even conservative extrapolation of that figure suggests Hatzegopteryx was among the longest-jawed non-marine tetrapods to have ever lived (Witton 2013). Such an unusual pterosaur seems fitting for its provenance, the Densuș Ciula Formation representing part of the ancient and peculiar 'Hateg Island' ecosystem. This setting will be familiar to many as an ancient, large Cretaceous island well-separated from the rest of Europe by deep seas, and populated by archaic, sometimes dwarfed or otherwise peculiar dinosaur lineages (e.g. Benton et al. 2010).
Since Hatzegopteryx was named in 2002 several Romanian sites of equal age and palaeoenvironmental setting have provided new fossils of giant pterosaurs. Some of them have a real Hatzegopteryx flavour (Vremir 2010; Vremir et al. 2013) and, although a complete specimen remains far from realised, a crude picture of this giant pterosaur is slowly being put together. These specimens are being worked on by different teams and, hopefully soon, we'll have a lot of new Haztegopteryx (or at least large azhdarchid) material to play with.
But that's not to say there's nothing new about Hatzegopteryx to discuss here. In fact, today Darren Naish and I published a new, open-access peer-reviewed form-function assessment of a Hatzegopteryx vertebra which takes us a step closer to understanding this enigmatic animal (Naish and Witton 2017). Long-term readers of this blog or Tetrapod Zoology will know that Darren and I team up semi-regularly to write about azhdarchid palaeobiology and may have played a role in shaping modern interpretations of these pterosaurs (Witton and Naish 2008, 2013). Our work this time focuses on a remarkable pterosaur bone known as EME 315, a giant azhdarchid cervical briefly described by Vremir (2010) and likely representing the first described axial element of Hatzegopteryx*. Our ideas about the proportions, structural properties and surrounding musculature of this bone are quite different to what has previously been said about Hatzegopteryx and other azhdarchids and, if we were sensible people, we would have kept quiet until today. However, our enthusiasm for the project and as well as a long, complex writing process has made for a particularly leaky embargo (artwork of our new interpretation of Hatzegopteryx made it into my art book, Recreating an Age of Reptiles, of instance) and many readers may be aware of our punchline: Hatzegopteryx may have a been a particularly powerful and 'short necked' azhdarchid, and maybe even a dominant predator of the topsy-turvy island ecosystem of ancient Hațeg. With the cat already somewhat out of the bag, let's take a look at our substantiation for what is a bold, counter-intuitive claim: could a pterosaur, even a giant azhdarchid, have been a formidable arch predator?
*EME 315 is from the Sebeș Formation, and thus not from the same formation as the H. thambema type, and does not overlap with our existing thambema inventory. However, it has the same characteristically thick bone walls, spongiose internal texture and stupendous size that we can recognise in the Hatzegopteryx type specimen. This, and its extremely close geographic and chronostratigraphic (Maastrichtian) occurrence, make referral to Hatzegopteryx reasonable, although we hedge our bets a little in not referring it to H. thambema itself. We settled on H. sp.
|Mighty EME 315 as presented in our paper. The scale bar represents 100 mm - for a pterosaur vertebra, this is a massive bone. Note the graph at the base of the image - for its size, EME 315 is a clear outlier to other azhdarchid cervical specimens. That's the Arambourgiania type cervical V for contrast. From Naish and Witton (2017).|
Estimating the neck length of Hatzegopteryx
Complete azhdarchid necks are rare, but we were able to track down data for six associated or reconstructed cervical series to plot their scaling regimes and predict the neck length for EME 315. These vertebral series also allowed us to make a predication for where in the neck EME 315 came from - we concluded that it likely represents a seventh cervical, one of the smaller vertebrae from the back of the 'functional' cervical skeleton. Our identification contradicts Vremir (2010), who suggested it was a third cervical, but there are good reasons to doubt this ID. Rehashing our long discussion of the vertebral ID here would be both tedious and unnecessary, especially given that interested readers can head to the paper for our full assessment. It will suffice to say that we're confident a cervical VII identification is much more likely than a cervical III, and this was the assumption we employed for the neck length estimate.
Our neck dataset predicted a cervical III-VII length of 1.5 m for EME 315, which sounds impressive, until you realise that the much smaller, 4.6 m wingspan azhdarchid i>Quetzalcoatlus
|Neck lengths in large and giant azhdarchids. A and B show Hatzegopteryx in lateral and dorsal aspect (B shows EME 315 and the holotype jaw bones only, but gives you an idea how chunky its neck was); C, shows Arambourgiania (known bones in white) with a reconstructed neck (grey elements); D and E, Quetzalcoatlus sp., lateral skeletal and dorsal view of skull and neck. From Naish and Witton (2017).|
Secondly, and perhaps of more general interest, this calculation adds to increasing evidence that azhdarchids may have differed rather dramatically in overall proportions. A number of workers have criticised the concept of azhdarchid anatomical uniformity in recent years (Vremir et al. 2012, 2013, 2015; Witton 2013), and our new paper adds further force to that argument: data for skulls, wing morphologies and now necks hint at a range of bauplans within the group. Their categorisation may not be as simple as 'robust' and 'gracile' forms as I've previously suggested (Witton 2013), but it's increasingly difficult to view Azhdarchidae as a parade of Quetzalcoatlus clones. This is of interest to not only researchers - differing forms might indicate differing behaviours and ecologies - but is something for artists to take note of too.
Arambourgiania vs. Hatzegopteryx: Neck Warssee the paper for details), but the TL;DR version is that the performance difference was consistently huge. OK, no-one was expecting the long, gracile Arambourgiania vertebra to outperform EME 315 in a bone strength competition, but the difference between the two is significant enough to indicate very different neck functions. Even comparing Arambourgiania's best bending performance against EME 315's worst, the latter is ten times stronger. We extrapolated our data to assess bending strength in the longest (and therefore weakest) neck bone in the Hatzegopteryx skeleton (a hypothetical cervical V) and it still outperformed its counterpart in Arambourgiania by several biomechanical miles. A larger cross-section, shorter vertebral body and thicker bone walls all contribute to EME 315's stellar bending performance, and we identify several additional aspects of reinforcement and strengthening of EME 315 in our paper.
It's therefore clear that the neck structure of Hatzegopteryx was in a different biomechanical league to that of Arambourgiania, and this implies vastly different neck functions in these species. We expect that one factor in this distinction is the wide, presumably heavy head ascribed to Hatzegopteryx, and infer that the weaker neck bones of Arambourgiania would require a narrower, gracile variant of the azhdarchid skull (maybe something a bit Q. sp-like). But the strength of the Hatzegopteryx neck seems high even accounting for its likely skull size, and we postulate that additional loads - big prey items, violent uses of the head and beak during foraging - may have contributed to its boosted structural properties.
Supporting this hypothesis are features indicative of large soft-tissue volumes around the neck of Haztegopteryx. Classically, the reduced features of azhdarchid neck vertebrae have seen them regarded - and depicted - with minimised cervical musculature and ligaments. We regard this view as problematic for a number of reasons. The first is that complete azhdarchid necks show that only the mid-series vertebrae lack complex anatomy indicative of muscle and ligament attachment. The complexity of their neck skeleton as a whole is not far off that of a 'normal' tetrapod, where the anterior and posterior vertebrae are relatively complicated to allow for greater volumes and intricacies of soft-tissues in these regions. Yes, azhdarchids do reduce their vertebral complexity further than most species, but not so far that we should assume their in vivo necks were little more than bony tubes covered in skin.
|Reconstructed cervical series and associated azhdarchid specimens show that their necks were not just made of bony tubes, but variably complicated bones in a pattern structurally typical of other long-necked tetrapods. What might this mean for soft-tissue development? One obvious implication is that at least the anterior and posterior neck regions were likely fleshier than often considered. From Naish and Witton (2017).|
Furthermore, assuming azhdarchid neck muscles and ligaments were basically homologous to those of living reptiles, some attachment sites must be regarded as expanded, not shrunken. These include particularly deep shoulder blades (for anchoring neck elevators and lateral flexors) and deep basins at the back of the cranium (for anchoring neck-skull extensors). While famously lacking vertebral processes on their mid-series cervicals, a suite of scars along the dorsal surfaces of azhdarchid cervicals betray long muscle or ligament attachments, while the vertebrae at the extremes of the neck have well-developed neural spines. Most startlingly, the expansion of their zygagpophyses take on new significance when we realise that these structures anchor numerous neck muscles in living sauropsids. So yes, azhdarchids certainly lost and reduced some areas of neck muscle attachment, but others were enhanced. The peculiar cervical anatomy of azhdarchids likely reflects an economising, rather than all-round loss, of neck soft-tissues.
Bringing this discussion of soft-tissue back to the giants, we have to look at Arambourgiania and Hatzegopteryx as once again reflecting very different types of animals. Our Arambourgiania cervical has much smaller areas for soft-tissue attachment compared to EME 315, which has immense, complicated anatomy in all the areas we associate with cervical soft-tissues in living sauropsids. This may partly be explained by EME 315 and the holotype Arambourgiania cervical being from different parts of the neck, but complete azhdarchid necks suggest these bones provide some general sense of neighbouring cervical skeleton anatomy - it would be weird if the Arambourgiania cervical V was juxtaposed with a massive, EME 315-type bone, for instance. We take this to indicate that EME 315 was not only a strong bone in a robust neck, but that the cervical skeleton of this animal was perhaps wrapped in large, powerful muscles and ligaments - exactly the sort of soft-tissues that can deliver those demands hinted at by our bending strength tests, and would be needed to wield that enormous head.
Ecological diversity of giant azhdarchidsThese results get most interesting when we plug them into the bigger picture of giant azhdarchid anatomy and lifestyles, because there seem to be a couple of different stories being hinted at here. For example, we can take the long neck, relatively low cervical bending strength and lessened areas of muscle attachment in Arambourgiania as placing restrictions on prey size as well as precluding violent, dynamic foraging strategies and other behaviours that would impart high stresses on its neck anatomy. Assuming the 'terrestrial stalker' model for azhdarchid lifestyles (Witton and Naish 2008, 2015) applies to the giants, we might imagine Arambourgiania as preferring smaller prey and relatively lightweight foodstuffs: smallish animals, the eggs of larger reptiles and birds, and generally anything that wouldn't put up too much of a fight. These would still be formidable animals - remember that they stand 4-5 m tall - but all indications are that they represent the 'lightweight' end of the azhdarchid palaeoecology spectrum, and likely behaved accordingly.
|Giant azhdarchid pterosaurs, diet edition. What we know of Arambourgiania implies they preferred smaller prey, such as diminutive dinosaurs, which may have been caught using relatively undemanding means.From Naish and Witton (2017).|
|The Hatzapocalypse: a group of foraging Hatzegopteryx find a chunky, subadult rhabdodontid Zalmoxes. Rather than pursuing baby sauropods or raiding nests, our interpretation of Hatzegopteryx implies it was a dangerous predator of mid-sized or larger animals. Whether it used the catchphrase "Hatze la vista, baby" after each successful hunt remains a matter of debate among scientists. From Naish and Witton (2017).|
Further work on new Romanian pterosaur fossils, as well as new discoveries, will show if this view is correct or not. Moreover, they'll help answer the many, many questions that remain concerning giant azhdarchid anatomy, evolution and palaeobiology. For me, among the most significant of these questions is what Hatzegopteryx signifies in the context of Late Cretaceous pterosaur disparity, ecological diversity and their eventual extinction. The latter is something we discuss briefly in our paper, as we've classically interpreted Maastrichtian pterosaurs as a biologically conservative group living on borrowed time. But our new work on Hatzegopteryx, as well as the potential recovery of a small-bodied pterosaur from Campanian sediments of Canada (Martin-Silverstone et al. 2016), and ongoing work on non-azhdarchid pterosaurs found near to the K/Pg boundary from Morocco (these being presented at SVPCA 2016 by Nick Longrich and colleagues) complicates that picture. It's looking more and more likely that our perception of the last pterosaurs as a low diversity, dying group has been distorted by sampling biases, and they may have actually been doing just fine until the end of the Mesozoic. Perhaps pterosaur extinction was a more significant event than previously realised.
But these questions will have to wait. For now, it's satisfying to finally be talking about these new data on what was clearly one of the coolest animals in the pterosaur canon. I'll leave you with a thought echoed from our paper: whether the ideas discussed here are right or wrong, the fact we can discuss 'the Hatzegopteryx arch predator hypothesis' without laughing is a real sign that interpretations of azhdarchids - and pterosaurs generally - have moved on considerably. Could our colleagues of 50-60 years ago have imagined pterosaurs - considered lame, underweight, creaky-winged gliding things - would be discussed in this sort of context? I imagine not.
(We're not done with pterosaurs, or new papers, at the blog just yet: stay tuned for more pterosaur news in the very near future.)
This paper, blog post and paintings are made possible by PatreonThe content featured here is sponsored by another group of short-necked tetrapods, my Patreon backers. Supporting my blog from $1 a month helps me produce researched and detailed articles with paintings to accompany them, as well as peer-reviewed papers on which to base them. In return for being a Patreon backer you get access to bonus blog content: additional commentary, in-progress sneak-previews of paintings, high-resolution artwork, and even free prints. For this post, we'll be looking the four years of development that went into the Hatzegopteryx painting shown above, revealing the earliest versions up to the final, published version. Sign up to Patreon to get access to this and the rest of my exclusive content!
A few years ago I wrote about how the 21st century is a terrific interval for palaeoart because of the wealth of information, discussion of palaeoart theory and diversity of talent we presently enjoy. Never before has so much data on this topic been available to practitioners of the trade, to scientists and historians, or to curious members of the public. The increase in palaeoart talent, a movement of artists exploring the outer regions of palaeoart science and artistry, and hints of wider interest in art of fossil animals are all traceable to these recent developments.
Any palaeoartist you speak to will tell you that there are honed practises and processes that should be applied when executing a palaeoart study. Several decades worth of influential artwork and writing by the likes of Knight, Hallett, Paul, Antón, Conway et al. and others send a unified message: reconstructions of fossil animals should be produced through close study of animal anatomy, both fossil and modern. They demonstrate that palaeoartworks must pass some basic, almost objective tests to be considered scientifically credible, successful examples of the medium.
In these artworks, even errors which scientists can objectively veto (such as proportions and bone articulations, elements of form such as skull or tooth shape, well-studied soft-tissue anatomies like feathers arrangements on dinosaur wings) are ignored. The result is that these pieces perpetuate errors that were realised as problematic years ago: under-muscled, 'shrink-wrapped' animals; 'bunny handed' theropods; feathered maniraptorans with three free fingers extending from their wings; ichthyosaurs with visible giant eyes; pterosaurs with enormous torsos and so on. The worst offenders show no grasp of basic aspects of animal anatomy, fossil or modern, with outlandish ideas of muscle distribution or proportions which are falsified by the most cursory glance at reference material. It is no exaggeration to say that some recent scientist-led palaeoartworks would not look out of place if produced in the 1830s.
And we - educators, scientists, palaeoartists - should feel ticked off about this. Scientist-led palaeoart should be the best there is: carefully-executed, evidence-led syntheses of research conclusions in compelling artworks. It should convey to people how the subject appeared and behaved based on both new, cutting-edge research and the best of the science which preceded it. There is no reason not to take the same attitude to our palaeoart that we do to the rest of our studies. It is frowned upon to take half-measure approaches to descriptions, statistical analyses or cladistic methodology, so why is palaeoart exempt? Making crass, basic errors in animal reconstruction is no different to executing a flawed study or analysis. Both ignore data, advice and theory documented in palaeontological literature, and both show little regard for the techniques developed by pioneers of the process. Moreover, when they make it to publication, both imply that half-baked approaches are worthy of equal consideration to more carefully executed examples. Scientists will know the feeling of frustration when work directly relevant to a paper is not cited: lousy palaeoart is guilty of ignoring the theory and development of an entire field.
A baffling aspect to this problem is that scientists routinely seek expertise lacking on research teams. Need a fossil prepared but lack the skulls? Seek assistance from a preparator. Need to crunch some stats but not sure how? Contact a colleague with statistical expertise. What we don't do with our science is assume our intuition and instincts about a topic are enough to guide us alone: we defer to those with the training, specific knowledge and experience to do the jobs we can't. And we would never employ an equally inexperienced individual and guide them through a process we lack all experience of ourselves.
But this is exactly what we do with palaeoartistry. Executing a palaeoart study requires a grasp of anatomy (and not just bones!), an ability to reconstruct/interpret fossil remains, a healthy grasp of living animal form, and an ability to translate all this into an artistic creation. These are not skills that everyone has, or that even all palaeontologists have. There are numerous specialisms in palaeontology, and not all of them are associated with the expertise ideal for consulting on palaeoartworks. Fossil bones do not exude a radiation which means those who work with them automatically know everything about palaeoart methods and theory. And yet it seems some scientists think it does, resulting in ill-founded advice for naive artists and approval of poor, flawed work. I am not the first person to raise this point (it has been mentioned in palaeoart literature since the 1980s), but it seems to fall on deaf ears.
Some readers may be wondering if this matters - so what if we have the odd wobbly looking reconstruction every now and then? Consider these points. Firstly, if scientists are so relaxed about palaeoart that they have no regard for even getting fundamental aspects correct, then what, really, is the point of the art in the first place? What can art of that quality really add to our field? It can't be held up as an accurate representation of the animal itself, and knowledgeable educators will avoid it or abandon it the moment a superior alternative becomes available (which, given the popularity of palaeoart online, is normally a couple of days after a new discovery. Indeed, awful PR palaeoart normally spurs more alternative versions, and with faster turnaround times). Badly produced palaeoart is basically destined to be ignored by those in the know, reflects poorly on those involved in its production, and ends up being an embarrassing aspect of the publication.
Lastly, it is widely known that the palaeoart industry has a problem maintaining employment for even its most talented individuals, and in this context hiring non-specialists, especially if the research team is not palaeoart savvy, is ludicrous - why not hire the right people for the job? There are many early-career palaeoartists available if tight budgets are a concern, as well as numerous veterans who can offer highly polished art and rapid turnaround times if time is tight. Finding these people is as easy as opening modern palaeoart books, asking colleagues for recommendations or even a Google search. The wealth of easily-accessed palaeoart talent makes it inexcusable not to bring specialist artists on board for palaeoart projects.
And 'inexcusable' sums up my feeling on this topic pretty well. The fact that many scientist-led artworks are really amazing shows that high quality palaeoart of this nature is achievable if scientists care enough about its production. But the availability of palaeoart-relevant information, the growing body of literature on palaeoart theory, the willingness and accessibility of talented artists, and the demands of modern scientific standards make academically-driven, scientifically-rotten palaeoart inexcusable in the modern day. I'm not arguing that scientist-led palaeoart has to be perfect. I'm not arguing that scientist-led palaeoart has to conform to specific conventions of style, or to constrained ideas of life appearance. But I am arguing that scientist-led palaeoart should look like someone gave a damn about the final product.
|Jurassic plesiosauroid Plesiosaurus dolichodeirus with a controversially dipped left hindfin. Nothing like a little drama to start a blog post.|
Despite their popularity among artists, the theory we apply to our plesiosaur reconstructions has not been significantly 'modernised' in the way that it has for other prehistoric species, most obviously Mesozoic dinosaurs, pterosaurs or fossil mammals. A number of authors and artists have produced solid foundations for the reconstruction of the latter animals - libraries of skeletal references, assessments of gait and stance, heightened awareness of common soft-tissues, etc. - and their life appearances are now more uniformly reconstructed and prone to fewer obvious errors. This has yet to happen for plesiosaurs, however. Modern skeletal reconstructions are few, references for muscle layout and soft-tissue data are fewer, and discussions over aspects of their life appearance are rare.
I was recently commissioned to produce two studies of two Early Jurassic plesiosaurs - one of the plesiosauroid Plesiosaurus dolichodeirus (above) and another of the pliosaurid Attenborosaurus conybeari (below). I cannot claim any expertise in plesiosaur science, but when reviewing art-relevant literature on these animals it struck me that many familiar elements of plesiosaur palaeoart oppose our soft-tissue data, modern muscle studies and flipper arthrology, as well as the generalities of vertebrate anatomy. I'm sure others have noticed these issues before me, but their prevalence in contemporary plesiosaur art suggests they are not as widely known as they could be. In the interests of stirring conversation on restoring plesiosaurs, I thought I'd share my findings and thoughts here.
Flipper shape and motionOne of the ‘classic’ elements of plesiosaur reconstruction is their distinctive flipper shape: a tight, oar-like profile which hugs the contours of the fin skeletons. However, both muscle studies and soft-tissue data indicate that their limb morphology was quite different to the underlying osteology, and our 'oar-like' depictions are problematic.
Firstly, reconstructions of plesiosaur forelimb musculature show that they were likely powerfully muscled around the shoulders, especially ventrally. Reconstructions of plesiosaur forelimb musculature have been around for almost 100 years and several alternative ideas on the exact configuration are available. They vary from sparingly muscled reconstructions where those massive, plate-like pectoral elements are left mostly free of muscle anchorage (e.g. Carpenter et al. 2010), to models where the entire girdle is swathed in huge muscle attachment sites (Araújo and Correia 2015). The latter seems to reflect the most phylogenetically-informed hypothesis (using data from lizards, crocs and turtles, which seems sensible given on-going uncertainty about plesiosaur ancestry) and - from a purely intuitive perspective - an extensively muscled limb girdle seems more likely than a lightly muscled one. Why develop those huge coracoids if they aren't going to anchor anything?
If the more extensive models of pectoral musculature are correct, we need to consider how the proximal regions of plesiosaur forelimbs would have looked like in life. One key consequence is that, once we link all the pectoral muscles to their insertions on the limb and body, the 'shaft' of the 'oar-shaped' flipper disappears: muscles running along the anterior and posterior region of the humerus fill the pinched, concave regions so that the proximal region is almost as thick as the bony paddle. Much of the proximal humerus becomes buried in muscle dorsally and ventrally too, to the extent that we might imagine the shoulder region was quite bulky in life.
|Hydrorion brachypterygius and its soft-tissue forelimb impressions (the dark, grainy textures behind the fins). From von Huene (1923).|
Aspects of the neckMy experience with the mass-economising, lightweight long necks of terrestrial or volant tetrapods means the extensively developed vertebrae of longer necked plesiosaurs are of great personal interest. Freed of the constraints of mass reduction, their numerous neck vertebrae are short, highly developed elements with long, robust processes - the exact opposite of the long, simplified structures I'm used to dealing with. Assuming plesiosaur necks were constructed like those of other amniotes (below), they likely anchored powerful muscles along their lengths. In particular, their neural spines are very tall and we can assume they bore enhanced musculature associated with lifting and turning the neck - useful features for long necked animals living in a dense fluid medium. Myological reconstructions suggest that the axial column would bear muscles connecting to the pectoral girdle, producing a deep set of tissues at the neck-torso junction (Araújo and Correia 2015, see pectoral myology diagram above). Artists should equip these animals with chunky, powerful 'reptilian' necks rather than svelte, bird-like variants. I do wonder if thick muscles along the neck might have impacted their neck mobility somewhat - another reason to assume long-necked plesiosaurs were only capable of bending their necks into simple curves (e.g. Zammit et al. 2008).
Trunk shape - cross section and lateral profilePlesiosaurs are often restored with a generic, 'barrel-shaped’ trunks. This is appropriate for some taxa, but not all. It must be said that plesiosaur torso shape is an area of on-going research. I recently spoke with a number of plesiosaur experts on this matter and found aspects like rib and gastralia articulation, the vertical position of the pectoral girdle and so on were somewhat contentious (thanks to Richard Forrest, Aubrey Roberts and Mark Evans for their thoughts). The crux of the issue is that, unlike some reptiles (such as birds or pterosaurs), plesiosaur torso skeletons don't slot neatly together in a single, incontrovertible manner, as is evident to anyone who's seen more than one plesiosaur mount in a museum. Understanding their torsos requires precise appreciation of their vertebral rib articulations, knowing their rib and gastralia curvature in three dimensions, and the benefit of fully articulated fossils for reference. This is quite a list of requirements, and one that is only currently met by a fraction of plesiosaur taxa.
Despite this, detailed reconstruction attempts provide reason to think not all plesiosaurs had tubby, barrel-shaped torsos. Close inspection of vertebral rib articulations and the shape of three-dimensionally preserved plesiosaur torso skeletons allowed O’Keefe et al. (2011) to reconstruct some cryptoclidids with tall, barrel-shaped bodies, and others with dorsoventrally compressed ones (below). In some genera, like Tatanectes, this is augmented further by almost flat dorsal ribs. It is difficult to gauge torso cross sectional shapes from just looking at a typical, half-prepared and flattened plesiosaur fossil, but artists should be mindful that not all species will have circular torso sections. Given how important torso shapes are to a reconstruction, we should check research literature carefully to make the most informed call we can on this aspect of restoring their life appearance.
|Cryptoclidid torsos in cross section, with (over conservative) soft-tissue outlines. Modified from O'Keefe et al. (2011).|
|Attenborosaurus conybeari, Jurassic equivalent of those top-heavy gym users who forget about working their legs.|
A recurrent theme in this post has been the idea of plesiosaur skeletons being deeply buried in soft-tissues of varying kinds. One of the most amazing plesiosaur fossils known to date, recently described from Cretaceous deposits of Mexico (Frey and Stinnesbeck 2014; Frey et al. 2017), clearly vindicates this theory. This specimen is the holotype of Mauriciosaurus fernandezi, which preserves a near-continuous body outline to give us an unprecedented glimpse of its life appearance. Much of the soft-tissue includes belly and lateral body wall skin impressions (tiny, 12 x 2 mm rectangular scales arranged in rows along the animal), but even more surprising is how much soft-tissue there is: by gum, this was a tubby creature, particularly around the tail. Even the thinnest regions of the outline are a good 50 mm wide, and some parts are considerably deeper. Frey et al. (2017) ascribe much of this depth to fatty, subdermal adipose tissue, including the caudal mass. Many living reptiles have extensive fat deposits around their tails (as discussed for prehistoric animals in this post) and it would not be surprising if plesiosaurs used this adaptation to streamline their shape. As noted by Frey et al. (2017), the preserved torso shape is not dissimilar to those of highly pelagic turtles or penguins.
And finally... so long, shrink-wrapping
|Line drawing of Mauriciosaurus fernandezi holotype, redrawn from Frey et al. (2017). This specimen is extra special for reminding us of the finest Queen song of all time.|
As a final point on the Mauriciosaurus fossil, we can now add plesiosaurs to the list of fossil taxa with specimens directly opposing 'shrink-wrapping' palaeoartistic conventions. It joins fossils of dinosaurs (Mesozoic and beyond), pterosaurs, mammals, early archosauromorphs and many others in suggesting the soft-tissues of long extinct creatures were no less extensive than those of modern species. As with living taxa, their skeletons were mostly placed well inside their bodies, not just under the surface of a thin skin. There's no doubt that soft-tissue depth is going to vary across animal bodies and between species, but it's increasingly difficult to defend reconstructions where bodies tightly hug skeletal contours, where facial tissues are sucked into every skull cavity, and where the depth of fats and integuments are not factored into the restorative process. 'Shrink-wrapping' is one of the few aspects of palaeoart that is testable against fossil data, and it is not winning out.
And that's that, thenI'm sure there's a lot more we could say on restoring plesiosaurs, but this is where we'll have to leave this discussion for now - hopefully this post helps fill the deficit of detailed discussion on plesiosaur life appearance. I must admit that these recent efforts at restoring plesiosaurs have given me a newfound interest in the group, and I wouldn't be surprised if artwork these chaps and their relatives turn up around here soon.
Next time: sharks vs. pterosaurs - who will win? (Spoiler: not the pterosaurs)
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Last month I posted a complaint about poor scientist-led palaeoart - those artworks of extinct animals produced under direct control of scientists to promote research, without any interference from TV companies or book publishers, and yet still end up being objectively flawed at a scientific level. I focused a lot of my criticisms at scientists themselves, as they have final authority over factual aspects of palaeoartworks. That doesn't necessarily clear artists from all blame, but it's naive to think that every artist tackling palaeoart has specific training in palaeontological matters, unrestricted access to technical literature, or the anatomical knowledge required to restore fossil animals without instruction. A scientist's main role in a palaeoart collaboration is bringing rigour and information to the table and, when science-led pieces are objectively poor, we have to wonder what happened to those guiding hands.
Our instinct might be to assume that lack of scientific rigour reflects flippancy towards palaeoart and its impact, and I think that is true - in at least some cases. But in a comment posted after my article, Matt Bonnan proposed that scientifically poor artwork might reflect scientists struggling with their role in the palaeoart process - that is, not really knowing how to instruct an artist, or where the line between scientific and artistic considerations lies. I can believe this is true, too. Lots of people - including many scientists and artists - view science and art as incompatible concepts, and are unsure how to approach projects blending the two. For some folks the idea of contributing to an art project is pretty terrifying, perhaps because they're afraid of being seen as naive, or of their contribution letting a project down.
Whatever the reason, I want to follow my previous criticism with something more constructive: some pointers for how scientists might approach their role in producing palaeoartworks. The take-home message is that scientists concerned about getting paint on their fingers shouldn't worry about the artistic aspects of paleaoartworks. The primary role of a scientist is not to understand colour hues, choice of media, composition and so on, but to comment on objective, factual components of the work. Is the restored species the right size in relation to other species and the environment? Is its head the right shape? Has it been restored with the right soft-tissue anatomy? Answering these and other questions do not require artistic training, or any special training at all for that matter, just application of knowledge that most palaeontologists will already have.
This discussion mainly considers scientists involved in producing a novel palaeoartwork, but will also apply to those reviewing artwork before publication or exhibition. This includes peer review of papers with palaeoartworks, and I encourage editors to make sure these aspects are checked alongside other parts of a paper. After all, if an artwork is being presented as scientifically-credible enough to be included in a peer-reviewed publication, it should be held to the same standards as the rest of the publication. I don't want to beat a dead horse by bringing this up again, but we should recall that palaeoart components can remain in use long after the context of their original genesis has been consigned to history, and artworks associated with papers can be especially prone to long-term use. We should take all opportunities to steer depictions of the past in the most credible directions, hopefully influencing subsequent generations of artists in the best way possible.
So, what should scientists look to critique in artworks, and how might they go about assessing credibility? A perquisite of guiding palaeoart processes is having a concept of what the subject species looked like. This might seem like a patronising comment, with experts replying 'of course I know what [subject species] looks like!', but really think about it - do you really know what the proportions of your subject are, and what they look like when reconstructed against one another? As in, to the point where you could render a reasonable stick-figure version of it? Could you describe what it looks like outside of plain lateral view, and are these interpretations based on modern technical data, not treatments of the same subject by previous artists? Palaeoart is highly varied in scientific credibility and even those works produced by masters of palaeoart may have dated or contain errors. Ergo, palaeoart consultants should form their basic concepts of appearance from images of fossils, tables of measurements and other primary resources, not previous artistic interpretations. This need for caution applies to skeletal reconstructions too, as these become dated and require modernisation as much as any other reconstructions of prehistoric life. So before dusting off that copy of Romer's Vertebrate Palaeontology for another round of consultancy work, or digging out a skeletal from a century ago, consider how kind the last few decades of research have been to those familiar images. Anyone needing an example of how a well-known, seemingly 'safe' skeletal can become dated should check out Scott Hartman's new Dimetrodon skeletal. The animal we all 'know' as Dimetrodon is really Romer's 1927 skeletal - 90 years on, it's looking pretty different.
|Is palaeoart a reliable source of information about the appearance of a fossil animal? Sometimes yes, but oftentimes, no. Talk slide from my 2014 TetZooCon presentation on the cultural evolution of azhdarchids pterosaurs, showing some of the earlier, zanier attempts to restore these animals. There's so much incredulous anatomy here that artists and scientists should steer well clear of these as reference material and go back to primary sources - fossils, descriptions, measurements - to form the foundation of their artwork. (Psst - TetZooCon is happening again soon, details here)|
Because of this, palaeoart consultancy is not as arduous a task as it first appears, nor a total time sink. I'm not going to pretend that good palaeoart consultancy is a job you can do in seconds but, once you have basic references established, most comments simply pertain to nudging the reconstruction in the right direction. As with many academic projects, advising on palaeoart requires the most time investment up front, and then relatively little after. Needless to say, the more prepared you are at the start, the less time investment is needed down the line.
And these points - basic as they might seem - will see just about any palaeontologist able to guide and shape palaeoart production. It should be stressed how continued checking along these lines can make an amazing difference to a palaeoartwork, and thus its success at capturing a hypothesis and future legacy. Correcting a scientific goof not only makes a picture more credible, but it often marks a division between a picture being artistically lacking and coming together. There's a reason artists of living creatures (including humans) are so obsessed with the anatomy of their subjects, and that's because it's essential to producing good artwork. Palaeoart is no different, so don't be shy: help your artist get the information and understanding they need to make your science look great.
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|A female Pteranodon tries to explain the new Silverstone et al. (2017) paper on Pteranodon taxonomy to the Cretaceous shark Squalicorax. Unfortunately for her, the sharks quite liked the 'Dawndraco' hypothesis.|
With my paper now out (though sadly not open access, but I will eventually be able to post an unformatted version online next year) I thought it would be a good time to take a holistic look at direct fossil evidence of pterosaur lifestyles. What are some of the most interesting examples of pterosaurs interacting with other species? Which purported interactions stand up to scrutiny, and which ones are a little tenuous? And what do they tell us about the all important Big Picture of pterosaur palaeobiology?
Yes, some pterosaurs may well have been seabird mimicsA number of pterosaur specimens have been reported as being associated with the remains of their last meals. Several of these have been lost, found to be erroneously interpreted, or are simply too poorly preserved to interpret their gut content. However, examples of the Jurassic non-pterodactyloids Rhamphorhynchus and Scaphognathus, the Triassic Eudimorphodon, and the famous Cretaceous taxon Pteranodon show reliable insights into their dietary preferences (below). These are virtually all remains of aquatic animals - mostly fish - preserved in intimate association with pterosaur skeletons, either between their jaws, aligned with their throats or within the torso skeleton. One example of a coprolite is known, though it's difficult to say exactly what it contains.
|Pterosaurs and their last meals (shaded grey). A, torso of Eudimorphodon; B-D, various Rhamphorhynchus with gut content and coprolite (C), E, Scaphognathus; F, Ludodactylus; and G, Pteranodon. From Witton (2017).|
But we can't maintain the older view that these specimens, on their own, undermine the increasingly diverse and nuanced takes on pterosaur palaeoecology hinted at by form-function studies, biomechanics, and modern understandings of pterosaur habitats. We have thousands of pterosaur specimens in museums around the world, of which gut content is known from less than a dozen examples, and in four species. That's not even enough to demonstrate the full dietary range of the species in question, let alone tell us about the ecology of all pterosaurs. Indeed, the scarcity of pterosaur gut content agrees with some new predictions of pterosaur lifestyles in that non-aquatic food sources now suggested for pterosaurs - insects, wormy things, fruits, small tetrapods - have limited preservation potential, particularly outside of Lagerstätten. When factored against common agents of taphonomy and preservation, these hypotheses predict empty bellies in many pterosaur fossils, which is what we find virtually all of the time. It is, of course, difficult to be certain of anything concerning negative evidence, but it's nevertheless useful to note this predicted match between modern ideas and fossil data.
|A selection of pterosaur foraging traces - beak tip impressions and scrape marks - from Jurassic and Cretaceous sites. The black-filled elements are the feeding traces, dark grey are manus prints, and light grey are footprints. From Witton (2017).|
Pterosaur feeding evidence: the 'close, but no biscuit' specimensInferring palaeoecological details from fossils can be tricky, and it is unsurprising that some purported insights into pterosaur diets and lifestyles are contentious. One of these is the famous and perhaps darkly comic circumstances surrounding the holotype skull and mandible of Ludodactylus sibbicki, a Cretaceous, likely fish-eating Brazilian ornithocheirid found with a sharp, pointed leaf between its lower jaw rami (panel F in the image above). Much of the 2003 description of this specimen (Frey et al. 2003) discusses this association and concludes that ingestion of these plant remains led to the death of the pterosaur. According to this story, the pterosaur accidentally scooped up the leaf, having mistaking it for its usual prey, stabbed the plant material on its throat tissues, frayed the end of the leaf trying to work it loose, but starved to death before it could dislodge it.
I must admit a little scepticism about this scenario. This is not because animals getting things stuck in their mouths is implausible, but because the story presented by Frey and colleagues is pretty presumptive. It infers a lot about pterosaur behaviour, foraging strategies, throat tissue strength and so on that we can't confirm at present. Moreover, the hyoid apparatus - the skeletal support for much of the throat and tongue tissue - is preserved lying on top of the leaf, despite the suggestion that the plant matter was deeply imbedded in the throat tissues. How did that work itself loose with the leaf fatally stabbed between the jaws? The answer to that question - as with a lot of questions about this association - would easily fall into speculation and special pleading about all manner of unknown quantities, and thus has little value to understanding fossil animal palaeobiology. Boring and po-faced as it is, I don't think the unusual Ludodactylus holotype provides enough information to tell us much about pterosaur behaviour, or how this unlikely fossil association came to be.
A similar observation might be made about insect specimens - a dragonfly and lacewing - from the Jurassic Solnhofen Limestone that have torn wings, allegedly from a pterosaur attack (Tischlinger 2000). The logic goes that these otherwise perfectly preserved insects cannot have been attacked by aquatic predators, or else they would have been eaten after their wings were damaged. Failed attack from an airborne predator that would not pursue the injured insects into water is suggested as more likely. Solnhofen deposits do hold pterosaurs that were almost certainly aerial insect hawkers - such as Anurognathus (below, see Bennett 2007 and Witton 2013) - and these might be ideal perpetrators in this scenario.
|Anurognathus ammoni was an insect-hawking pterosaur that lived over the Solnhofen lagoon. Has it left feeding traces on fossil insect wings after a failed attack?|
Pterosaurs vs. dinosaurs, crocodyliforms and... the revenge of the fishThe fossil record gives us an insight on the question "did pterosaurs taste good?", and that answer seems to be "yes". Bite marks, embedded teeth and vomited pterosaur remains indicate that dinosaurs, crocodyliforms and fish all ate pterosaur flesh, at least on occasion (below). Among the more impressive examples of these interactions is a spinosaurid tooth, likely from the Brazilian spinosaurine Irritatorchallengeri, embedded in the cervical vertebra of an ornithocheirid (Buffetaut et al. 2004). Alas, no other evidence of their interaction was evident on the specimen (a series of pterosaur vertebrae) and it's not possible to ascertain much about circumstances that brought these species together.
read more about them in this post - some of the specimens are exceptional and there's lots to say about them. One of the more famous examples of piscine-pterosaur consumption - an Italian, Triassic pellet composed of alleged pterosaur bones (Dalla Vecchia et al. 1989) - has recently been reappraised. It's now more reliably interpreted as vomit ball made of bones from the tanystropheid Langobardisaurus (Holgado et al. 2015).
Lesser known, but pretty darned awesome examples of fishes eating pterosaurs are Pteranodon specimens that found themselves at the wrong end of Cretaceous sharks. Several Pteranodon bones reveal bite marks and even embedded teeth from two genera of sharks, the 2-3 m long 'crow shark' Squalicorax and the larger, 6 m long 'ginsu shark', Cretoxyrhina. The former seems to have eaten Pteranodon flesh on several occasions, while evidence of the latter is only currently known from a tooth closely associated with a cervical vertebra (panel F, above). Further work on the latter specimen is currently underway.
Feeding traces from these sharks are common in Western Interior Seaway fossils and those of Squalicorax are particularly abundant and taxonomically indiscriminate. Given that even giant marine reptiles are among the species consumed by this mid-sized shark, it's often assumed that this animal was a scavenger, biting into whatever free meat floated about America's continental sea. However, it is less certain that Pteranodon was scavenged by Squalicorax, as even a 2 m long specimen would vastly outweigh the largest Pteranodon. It is not inconceivable that an unwary Pteranodon could be grabbed and killed by a stealthy Squalicorax, though I stress this scenario is no better supported than the shark simply chancing acrossa Pteranodon carcass. Whatever the scenario, it's somewhat grounding to think of a weird extinct creature like a pterosaur being devoured by a fairly conventional-looking shark. It's a reminder, perhaps, that Mesozoic life was not a pantomime of exotic, giant reptiles and weirdo evolutionary experiments, and that much of our modern ecosystem was in place many millions of years ago.
The big picture
Looking at the pterosaur palaeoecological record holistically, what patterns emerge? If we look at where the record focuses phylogenetically (below), it's obvious that our records are significantly biased towards certain taxa - Pteranodon, Rhamphorhynchus, and azhdarchids. Even their close relatives, with similar anatomy and adaptations, preservational conditions and so on, don't get much of a look in. There's a few data points scattered here and there, but tumbleweeds run though the palaeoecological data stores for the majority of the group.
|Attempting to make sense of the pterosaur palaeoecological record in a holistic way mainly shows how paltry this record remains. It's improved a lot in recent years, but we await evidence of diet and consumer-consumed relationships in virtually all major pterosaur clades. The images at the bottom of this figure are takes on known examples of pterosaur ecology: Rhamphorhynchus ingesting fish, and azhdarchids being devoured by dromaeosaurs. From Witton (2017).|
My take on all this is that there must other factors at play here. We don't get evidence of pterosaur palaeoecology just by throwing more fossils, or better quality fossils, into the mix. I'm sure these factors have some role, but perhaps only in concert with special traits of certain pterosaur groups - maybe behaviours and anatomies - that allow them to have good records. We might have a good record of azhdarchids being consumed by dinosaurs and crocs, for instance, because their bones are often quite big and allow predators to bite them without destroying them. Perhaps we have good palaeoecological insights for Rhamphorhynchus and Pternanodon because of their habits and behaviour - both have strong aquatic adaptations (see this blog postfor ideas on that), and there is a bias towards preservation of aquatic animals in the fossil record. Perhaps this aids preservation of not only palaeoecological data, but also explains why these taxa are our most abundant pterosaurs (>100 Rhamphorhynchus fossils are known, >1000 Pteranodon).
The pterosaur palaeoecological record, then, is perhaps in a transformative state. Though vastly improved over its condition a few decades ago, it requires further augmentation to provide us with significant insights into pterosaur lifestyles, and to explain its biased nature. However, we should not be too pessimistic about the insight it offers into pterosaur palaeobiology: it still provides useful datapoints that can shape our interpretation of flying reptile ecology for several species. Cliched as it is, the take-home message of this project is that any palaeoecologically-relevant pterosaur fossils are worth putting on record. We still have a lot to learn about how these animals lived and behaved, and direct insights are the most reliable ways to do that.
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|Benjamin Waterhouse Hawkin's (1858?) sketch of amphibious marine reptiles, including a large shambling ichthyosaur. Image borrowed from Frank T. Zumbach's Mysterious World.|
Of course, art has a habit of imitating life and, a good 150 years after amphibious marine reptiles became unfashionable in palaeoartworks, Ryosuke Motani and colleagues (2014) published a new marine reptile suggested to be capable of locomotion on land as well as in water: the ichthyosauriform Cartorhynchus lenticarpus. This Chinese, Early Triassic species is anatomically remarkable in several respects. Although reminiscent of early ichthyosaurs in overall shape, it has a considerably reduced snout, seems to lack teeth, is just 20 cm from snout to vent despite indications of osteological maturity, and bears enormously long forelimbs. Though unique when first discovered, another, much larger Cartorhynchus-like species has since been found in the same deposits, Sclerocormus parviceps. Together, these animals form a clade at the base of Ichthyosauriformes known as Nasorostra, the 'nose beaks', referring to a defining feature where their nasal bones reach the jaw tip (Jiang et al. 2016).
|Holotype specimen of Cartorhynchus lenticarpus. Note the enormous forelimbs with their expansive unossified wrists, indicated by the distal phalanges being well posteriorly displaced from the upper arm bones. From Motani et al. (2014).|
The functional basis for an amphibious lifestyle in CartorhynchusMotani et al. (2014) present a fairly detailed argument in favour of amphibious habits in Cartorhynchus. The chief lines of evidence are those expansive forelimbs, but it's not just their size that matters: their enormous, unossified carpal regions are also significant. Several early ichthyosauriforms have poorly ossified carpal bones but the unossfied region in Cartorhynchus flippers is proportionally bigger by some margin. This would allow these ordinarily-rigid marine reptile flippers an unusual degree of flexibility and optimise them for terrestrial locomotion. Flipper-based terrestrial motion is surprisingly tricky because its users tend to be suboptimally designed for movement out of water and they almost always have to overcome drag forces acting on the body as well as shove themselves around. Moreover, substrates associated with coasts and waterways tend to be unstable, yielding under pressure and being challenging for even proficient terrestrial animals. These factors mean flippers can easily dig into substrate or slip across it rather than propel their owners about, and it's easy to see why beaching is fatal for so many specialised aquatic species.
Studies (using robot turtles!) suggest that rigid flippers are generally poor at terrestrial locomotion and may even be incapable of moving animals over some surfaces (Mazouchova et al. 2013). A bendy flipper, in contrast, works well, allowing the forelimb to flex before the substrate moves, spreading the weight of the animal over the distal limb and allowing the proximal flipper region to elevate and support the body (Mazouchova et al. 2013; Motani et al. 2014). The unusually expanded flexion zone in Cartorhynchus forelimbs would be well suited to this purpose, and certainly much better at this task than those of other ichthyosaurs. We might note, as an aside, that the lack of flexion zones in other marine reptile flippers, such as those of plesiosaurs, might be good reason to doubt their ability to crawl over land.
The downside of having lots of cartilage in a long flipper is that they are weaker against bending than a more ossified one, so their utility as a walking limb lessen as the forces involved in moving the body increase. It's here where the small size of Cartorhynchus comes into play. Small size equates to low body masses and smaller forces associated with lifting the body, less structural demand on the flipper, and reduced drag effects from the sliding belly. As is so often the case in evolution, small body size might be an enabler for evolutionary experimentation in Cartorhynchus, allowing it to perform feats that its bigger relatives just couldn't even if they were also equipped with giant, bendy fins.
The tail of Cartorhynchus is incompletely known but it's anatomical and phylogenetic proximity to the completely-known Sclerocormus suggests that its tail was long, flexible, and lacked any sort of fin or fluke (Jiang et al. 2016). A relatively simple tail lessens the risk of it dredging sediment or catching on debris during terrestrial locomotion and its flexibility might have permitted its use as a prop or even propulsive organ: fish such as the Pacific leaping blenny show how a long, bendy tail can be used to powerful effects in semi-terrestrial locomotion (Heish 2010, also below). Combinations of fin and axial motion in land-crawling fish can be surprisingly effective over a range of substrates (Standen et al. 2016) and we might assume similar options were available to Cartorhynchus.
Cartorhynchus in contextIt seems there's a prima facie argument for considering Cartorhynchus as equipped with some amphibious features. However, we should not get carried away - a suite of evidence for an aquatic lifestyle suggests it wasn't it a specialist denizen of shallow, partly-exposed habitats, but more of an animal able to exploit two realms. It has pachyostotic bones, true flippers rather than webbed walking limbs, and is adapted for suction-feeding: a mechanism where the combination of a small mouth and a large oral cavity creates a pressure differential during feeding, literally sucking small prey into the mouth if it's opened quickly (Motani et al. 2014). This foraging strategy cannot work outside of water so is strong support for Cartorhynchus foraging in fully aquatic settings.
Cartorhynchus also stems from the Nanlinghu Formation, a mudrock and limestone marine deposit rich in fossils of aquatic reptiles and marine invertebrates: ammonoids, bivalves and conodonts. We might take these data as signs that Cartorhynchus was quite happy in water and maybe spent most of its time there, visiting coastlines and beaches on occassion, rather than living there permanently. We should also regard it as a marine animal, not an inhabitant of rivers or swamps (though it would be extremely cool if one turned up in such deposits!).
|Holotype of Hupehsuchus nanchangensis, a marine reptile seemingly more closely related to the ancestor of ichthyosaurs than Cartorhynchus. These guys surely deserve their own blog post and painting at some point. From Carroll and Dong (1991).|
What about Sclerocormus?
|Holotype specimen of the larger nasorostran species, Sclerocormus parviceps. From Jiang et al. (2016).|
So, walking with ichthyosaurs?
|And finally, a painting: Cartorhynchus goes for a drag around a Triassic lagoon.|
Or maybe more robot turtles. Either is good with me.
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Reinforcing skin to make armour and skin projections
|Indian rhinoceros skin in all it's supercollagenous glory. Note the thick folding but otherwise sparse wrinkling, a consequence of poor elasticity in this skin type. From Wikimedia user Sanjay ach, CC BY-SA 3.0.|
|American white pelican with rostral crest, photographed by Travis Barfield. Photo from Wikimedia.|
Collagen-dense armoured dermis leaves relatively coarse (1-2 mm) rugose projections of bone beneath it, often of sufficient extent that they are discernible in photographs. You can readily see them on rhino skulls, for instance, as well as around the jaw tips of hippos and the rostral bosses of red river hogs. They have a corresponding histological signature, too: patches of obliquely-orientated metaplastically ossified dermal collagen fibres (Hieronymus 2009; Hieronymus et al. 2009). These patches of rugose bone cover large areas of the skull, and, in hippos, they even wrap into the mouth, betraying the presence of soft-tissue armour inside the jaws. This is something for palaeoartists to note as it shows dense, armoured skin can grow around complex structures, like gums and teeth, and also allows for lip-like structures that sheath teeth (so no, these tissues are not excuses for toothy prehistoric artwork). I assume the stiffness of armoured skin explains why the 'canine pocket' in the hippo upper jaw does not collapse when gaping, despite their lack of skeletal reinforcement.
|Business end of a hippopotomus skull - note the rugose textures around the end of the snout, characteristic of collagen-dense armoured skin. Cropped detail from a CC BY-SA 3.0 photo by Wikimedia user ContinentalEurope. From Wikimedia.|
Where can we find these structures in the fossil record?
|Spoilers: in species like this guy. Mmm... abelisaur fresh...|
|Majungasaurus crenatissimus skull, showing extent of bone texture related to armoured skin (blue) and tough cornified skin (purple). Skull drawn from Sampson and Witmer (2007); distribution of bone textures after Hieronymus (2009).|
Evidence of epidermal structures are common in a paleaoart mainstay: pterosaurs. By now, most of us will be familiar with the idea that many pterosaurs had soft-tissue headcrests thanks to well-publicised exceptionally preserved fossils (e.g. Bennett 2002; Frey et al. 2003), but can we predict them in species represented by bones alone? Thanks to bone textures, we can. Soft-tissue crests grow over low bars of bone projecting from pterosaur snouts, often with expanded anterior regions (Bennett 2002). Fine, curving striations and spicules are discernible on the top of these projections, contrasting with the smooth bone forming the base of the bony crest and the rest of the pterosaur skull. These rugosities mostly project vertically, or somewhat anteriorly at the front of the base structure. It is difficult to know if these rugose regions have a ring-like distribution given the flattened nature of most pterosaur fossils, but their presence around the top of a projecting bone bar implies a ring-distribution. Collectively, these components meet predictions for epidermal projections and their distribution points to a tall, narrow structure - a crest - rather than a horn or boss. We would likely see this as the most parsimonious take on pterosaur crest bases even without exceptional fossil preservation so, wherever you see these features on pterosaur skulls, it is reasonable to assume a large, prominent crest. I stress that you do not these features in all crested pterosaurs: some bony crests are completely smooth, and have no evidence for extensive soft-tissue elaboration. This is mainly seen in the ornithocheiroids (the group that includes taxa like Anhanguera, Pteranodon and Nyctosaurus).
|Darwinopterus robustodens as a case study for pterosaur striated crests, and what they mean for soft-tissues. Yes, they were that daft - don't feel you need to be conservative when restoring them!|
Applications to other species, and potential pitfalls
There are some caveats and pitfalls to be aware of about predicting tough dermis and epidermal projections. For example, there are a few cases where skin elaborations lack osteological correlates. Warthog warts, for instance, are prominent, permanent and conspicuous skin structures, but they leave no trace on the underlying bone. Likewise, the presence of armoured skin becomes difficult to predict beyond the skull because postcranial bones tend to be buried under other soft-tissues. We know from living animals that collagen-dense skin can be regionalised (mouse deer, for instance, tend to localise it on their dorsum and rumps - Dubost and Terrade 1970), so evidence of cranial armour is only a partial indicator for armouring across the body.
|Cuspicephalus scarfi regrets sporting a hunk of tall, cornified cranial epidermis on a windy day.|
That final point seems particularly relevant given the modern palaeoart fashion of speculating about fossil animal appearance. Long-time readers will know that I'm an advocate of this practise, but science of the kind discussed here puts an onus on artists to be careful when adorning extinct animals with elaborate skin structures. Yes, there are loopholes which can justify these outlandish reconstructions if we want to find them, but consider that some speculative structures included in modern palaeoartworks would be expected to leave osseous markers if they were present. Maybe this is a case where absence of evidence is actually evidence of absence and, if we cannot find these correlates, we should assume those structures were not present in our subject species.
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|Reworked version of my 2012 Tyrannosaurus painting, now in it's third guise. There's something about this painting which recalls reconstructions from 1906 rather than those of 2016.|
In the recent months two papers have challenged this idea. The first, by Thomas Carr and colleagues (2017), purports to find osteological correlates of scales on the facial anatomy of the tyrannosaurid Daspleteosaurus, which they argue (along with other lines of evidence), to suggest crocodylian-like facial tissues and sensitivity. The second, by Phil Bell et al. (2017), describes scaly skin impressions from multiple postcranial regions of a Tyrannosaurus skeleton, and argues that the distribution of these impressions implies a uniform (or near uniform) covering of scales across the body, without much in the way of fuzz.
Because this is Tyrannosaurus, media sites and bloggers have spilled great amounts of ink over these stories. The scientific press has often been far from objective or unbiased. Popular articles have suggested Jurassic World fans might have 'won' the debate over scientists, that science fans are 'due' a return to scaly tyrants after 'losing' Pluto, and that the findings mean 'all is well in the dinosaur world'. The implication is a ridiculous one, like evidence of scalier tyrants is a moral victory rather than a test of a scientific hypothesis. But while the popular press has been celebrating the new papers, members of the palaeoblogosphere have been less enamoured with the findings. Trey the Explainer suggests that Bell et al.'s work doesn't really change what we already knew about tyrant integument, and thus does not invalidate many existing reconstructions. Andrea Cau posits that interpretations of scaly tyrants reflect our prejudices more than science, and that taphonomic factors may explain the absence of filaments. Brian Switek has concerns that the skin patches are too small and spread too widely to give a complete picture of the integument, and echoes concerns about taphonomic interference. The collective response seems to be a defensive one, protecting concepts of filamented tyrannosaurids from a resurgence of a more traditional, scaly model. Would any other dinosaur get this treatment? Perhaps not: as Brian explains in his recent post, this reaction is the T. rex celebrity effect at full bore.
|Supermegafluffy Tyrannosaurus, from 2015. They were simpler times.|
What, exactly, has been argued about scaly tyrants?A lot of the popular write ups of these recent papers include errors and misrepresentation, so let's recap what is actually being argued about Tyrannosaurus skin. A common social media reaction to Bell et al.'s work is that they've presented 'a patch' of skin, and are extrapolating from that. We need to debunk that right away: they've not described a single patch, but multiple small patches from the neck (alas, exactly where on the neck isn't reported), the top of the pelvis, and the base of the tail (below). All the samples stem from the 'Wyrex' specimen (HMNS 2006.1743.01). The most extensively represented area is the tail base, which has the largest single piece of fossil skin - 30 cm². The other skin samples are not as large, some being just a few centimetres across. Each patch shows the same skin type: uniform, tiny 'basement scales', each less than 1 mm across (Take note, artists: you would not see Tyrannosaurus scales until you were being eaten by their owner). Similar scale patches, also described by Bell et al. (2017), have been found on the torso and tail regions of other tyrannosaurid species, implying similarly scaled regions in these taxa.
|Tyrannosaurus skull AMNH 5027 - note the 'hummocky' textures on the side of the snout, above and below the orbit, and atop the rostrum, likely indications of scaly skin. Image in public domain, sourced from Wikipedia.|
|Everyone's doing maps of Tyrannosaurus with integument details nowadays, and I want in. Note that this is Tyrannosaurus specific, and does not feature scale data from other tryannosaurids.|
What's in the gaps?The million dollar question is what was present between these scaly regions: more scales, or fibres? This is a major point for many respondents to the Carr et al. and Bell et al. papers, as it decides whether we keep our interpretation of Tyrannosaurus as an - at least partly - fuzzy animal. With our scale distribution map as a starting point, several options are available. The first is that fuzz was present in regions not yet represented by skin remains or osteological correlates. This would mostly imply the top of the torso (Bell et al. 2017), but may also be parts of the back of the head, some aspects of the neck (depending on where the neck skin impression came from) and maybe the end of the tail. Over on Twitter, Patrick Murphy has presented a reconstruction which shows what this might look like. I must admit to finding it quite amusing, sort of like T. rex has put on a shawl to visit the opera.
But how dense could these fuzzy patches have been? Bell et al. (2017) suggest that dense fibrous coverings are doubtful, noting that large living mammals avoid patches of thick insulating fibres to aid heat loss. This has not gone down well with some critics, who cite studies of feathers preventing over-heating instead of facilitating it. An oft-cited study in this regard is Dawson and Maloney (2004), who found emu feathers block virtually all solar radiation from the skin, preventing them from overheating in solar exposure that causes similarly-sized hairy mammals to seek shelter.
|Feathers: great at blocking solar radiation, also great at trapping body heat. Note how cooking hot these ostriches are on their necks, heads and legs, while the feathers are mostly ambient temperature. This isn't because the body isn't warm, but because the feathers block the heat signature entirely, trapping all that heat around the body. As surface area:volume ratios drop as animals get larger, it stands to reason that the benefits of blocking solar radiation give way to a need shed heat. Image from Wikipedia user Arno / Coen, CC BY-SA 3.0.|
If living birds find feathers a little warm, despite their relatively high surface area to volume ratios, we have to assume a theropod weighing anywhere between 6-14 tonnes is going to find big areas of dense filaments a challenge to thermoregulation too. It is not unreasonable to assume blankets of fibres could be a problem for big tyrants. The counterargument here is that Yutyrannus huali, a largish tyrannosauroid, does have dense fibres everywhere. But Yutyrannnus seems more lithe than Tyrannosaurus - perhaps just 10-25% of its mass, depending on the estimates (Bell et al. 2017) - and lived in a more vegetated, and thus shadier, habitat (Bell et al. 2017). A neat comparison Bell et al. (2017) make along this line uses living rhinos, where hairier species live in shadier settings than the virtually naked ones. In light of this, the reduction of filamented regions, and perhaps lessening their density, is a reasonable inference for animals of the size and habitat of Tyrannosaurus, and would reflect thermoregulatory responses to scaling and shade availability seen in living animals.
|Large tyrannosauroids, like Yutyrannus huali, show that dinosaurs weighing perhaps 1.5 tonnes could be covered in feathers. But does this reflect the fact that this animal lived in shadier, vegetated habitats than the tyrannosaurids? This idea isn't silly: adaptation to specific circumstances has a major role to play in shaping animal skin anatomy, and could well explain why some tyrants are fuzzy, and others seem less so. (If you want to see the rest of this picture, check out this Patreon post)|
|Scaly, minimally-filamented Tyrannosaurus. There's some tufts on the neck, but that's it. Is this model more consistent with the thermoregulatory requirements of a 6-14 tonne animal?|
Beyond Tyrannosaurus: 'unlocking' dinosaur skin constraintsMy take-home from these new papers is that our models of Tyrannosaurus skin have not crystallised, but we're a little more constrained in how we can imagine this animal, and have to concede a scalier appearance than many of us thought likely. But the implications of the Bell et al. study go beyond Tyrannosaurus in implying new ways to think about dinosaur skin evolution. With incontrovertibly fuzzy animals lining much of the the tyrannosauroid tree and its root, our scalier Tyrannosaurus gives us one of the best examples of a dinosaur replacing fuzz with scales. This is a far-reaching conclusion for those of us interested in dinosaur life appearance, complicating the already confusing evolutionary pattern of scale and fuzz distribution within the group. Ideas that some dinosaurs could be 'secondarily scaled' are supported by this discovery, and we have to wonder if classically fuzzy lineages - including many other theropod lines - are as tightly locked into fuzz, fibres and feathers as we once thought. Could large dromaeosaurs be a little lighter on fuzz than we imagine? Did Therizinosaurus look less like a giant pigeon and more like a walking Christmas dinner? We don't know, but now have reason to wonder.
|Fluffy Tyrannosaurus juveniles, one of the possibilities created by the idea that tyrannosaurs might have avian-like 'dynamic' skin. The recovery of scales in non-scaly clades is not as simple as it might first appear!|