Starring front and centre in the image Nyasasaurus parringtoni, the 2-3 m long possible dinosaur (or extremely dinosaur-like dinosauriform) from the Middle Triassic Manda Formation of Tanzania. As anyone with an ear to the ground for palaeontology news will know, Nesbitt et al. (2012) have rescued Nyasasaurus from the nomina nuda bin and made a compelling case for it to represent the oldest dinosaur remains yet known, or at least a dinosauriform species that was only a evolutionary stones throw from Dinosauria proper (see Nesbitt et al. 2012 for full details, or one of the many write ups populating the Internet). Unfortunately, Nyasasaurus is known from only a handful of scrappy bones including a few vertebrae and a partial humerus, which doesn't give much to work from for an artist. Paul Barrett and Sterling Nesbitt, the brains behind this image, suggested that another ancient dinosaur, Eoraptor, should be the primary reference, but with a some influence from early sauropodomorphs. The result is an admittedly slightly speculative animal, but one that hopefully captures the generalised anatomy that may have been common to the first dinosaurs and their immediate ancestors. The question of integument, a crucial consideration for any modern image of a Mesozoic dinosaur, was addressed fairly quickly: "...definitely no feathers!" It's funny to think that palaeontologists now have to defend the choice not to cover their dinosaurs in feathers or other fancy integuments, but I don't disagree with the decision here. Feathers are spreading down towards the base of Dinosauria at a rapid rate, but direct evidence is still some distance from the root of the tree. Of course, the occurrence of fuzz in pterosaurs, which some authors have already controversially interpreted as representing early types of feather, does create the potential for fuzzy integuments in all ornithodirans, but we're still waiting for smoking gun evidence of this. Elaborate restorations of prehistoric animals are definitely in fashion at the moment, but we do need to keep perspective on what the fossil record tells us. In the absence of fuzz, I chose the wrinkly, dappled scales of a perente monitor as the inspiration for the Nyasasaurus skin.
At least part of the rationale behind the dabbled, camouflaged tones of the centre animal came from its likely place in its Middle Triassic ecosystem. Nyasasaurus and other dinosauriforms were minor faunal components of a world dominated by other types of reptile (Nesbitt et al. 2012), so they may have done well to remain largely remain inconspicuous for much of the time. The rhynchosaur Stenaulorhynchus (see image detail above, showing the rhynchosaurs in all their inelegant glory) seems to have been a particularly common animal in the Manda Formation, with dozens of individuals being found compared to the one occurrence of Nyasasaurus. We wanted to feature this ecological relationship in the image, showing a lonely early dinosaur in a landscape controlled by other animals. Rather than simply including a bunch of Stenaulorhynchus in the distance however, we thought it would be cool to have the Nyasasaurus following a trail of destructive rhynchosaur foraging. Rhynchosaurs are noted for their adaptations for scratch digging with their hindlimbs, which may have been used to unearth roots, tubers or other food (Benton 1983, 1990) . In this image, several shallow excavations have been made by a troop of Stenaulorhynchus in their quest for food, which the Nyasasaurus is picking over to nab exhumed invertebrates and nutritious plant matter left behind. I must admit that the charisma of Stenaulorhynchus almost stole the show for me when drawing the image: I didn't realise how cool digging, buck-toothed reptopigs were, and I think the depiction of them digging is a first for palaeoart generally.
Finally, a quick word on the environment. Say 'Triassic climate' to most folks and their thoughts will travel to arid, barren landscapes, but this is only true for the latter half of the Triassic. The Early and Middle Triassic (which account for only the first 40 % of Triassic time) were rather wetter and, presumably, lusher than we usually imagine them (e.g. Benton 1983). In keeping with this trend, the Manda Formation palaeoenvironment was a fairly mesic, temperate setting that was likely a lot greener than the Triassic scenes we're used to. And that will have to do for now. So much for a 'brief' post. Again.
References
- Benton, M. J. 1983. Dinosaur Success in the Triassic: A Noncompetitive Ecological Model. The Quarterly Review of Biology, 58, 29-55.
- Benton, M. J. 1990. The species of Rhynchosaurus, a rhynchosaur (Reptilia, Diapsida) from the Middle Triassic of England. Philosophical Transactions of the Royal Society of London. Series B, Biological Sciences, 328, 213-306.
- Nesbitt, S. J., Barrett, P. M., Werning, S., Sidor C. A. and Charig, A. J. 2012. The oldest dinosaur? A Middle Triassic dinosauriform from Tanzania. Biology Letters, 9. doi. 10.1098/rsbl.2012.0949
