So, here's something you don't see every day: giant azhdarchid pterosaurs and sauropods, living together in peace and harmony. Well, living together, anyway. This azhdarchid looks like a bit of a jerk, what with his swooping down to buzz the local titanosaurs for no obvious reason. They don't seem to like him very much.
We can be confident that giant azhdarchids and gigantic sauropods once coexisted. Both are known from Maastrichtian age rocks in North and South America, and two celebrity Mesozoic species, the famous titanosaur Alamosaurus sanjuanensis and giant azhdarchid Quetzalocatlus northropi are denizens of the Javelina Formation of Texas. Newly discovered vertebrae of Alamosaurus have boosted its maximum size estimates considerably, demonstrating it attained similar proportions to the gigantic titanosaurs of South America, Argentinosaurus and Puertasaurus (Fowler and Sullivan 2011). But while we can be certain that these giant animals occupied the same landscape, there's a lot of slop in trying to reconstruct them. Accordingly, I should stress that the animals depicted here are fairly generalised because, hand on heart, we don't know much about their appearance at all. Even basic attributes like their overall size are difficult to pin down. I thought Fowler and Sullivan (2011) were sensible for not including some shonky estimates of length or mass in their recent work on the new giant Alamosaurus material. Being simply content to say it was 'as big as Argentinosaurus and Puertasaurus' and 'among the largest sauropods in the world' works for me. Mike Habib and I took the same approach for the giant pterosaur Arambourgiania in our 2010 paper on giant pterosaur flight (Witton and Habib 2010). Arambourgiania is a probably the least known giant pterosaur among laymen, and is only represented by a few scrappy bones from Maastrichtian deposits of Jordan. The most impressive and discussed of these is its incomplete, 660 mm long neck holotype vertebra. But how does that link into the rest of its anatomy? Despite the propensity and popularity of reconstructions of giant pterosaurs, the truth is that we actually have very little idea of their dimensions and scaling regimes. Even the widely reported 10 m span for Quetzalcoatlus northropi is based on (unpublished) extrapolation from an animal half its size. Accordingly, it's difficult to say for certain how large Arambourgiania was, other than that it clearly had a very long neck (2.9 m is my most recent estimate for the combined length of Arambourgiania cervicals III-VII) and was probably among the largest pterosaurs we know of. That's not as cool as saying we know it spanned 11-13 m or whatever, but it's probably more honest.
Size is, of course, only one aspect to consider. Specific proportions and anatomies are pretty much impossible to reconstruct for many giant species, so I figure there's no point pretending that we really know what they look like. In 99% of cases, we're better off not kidding ourselves by saying "I'm painting [precise giant species]", but instead just acknowledging that we're rendering fairly generalised giant variants of their probable anatomy until we can refine them with new fossil data.
Righto, blogging time is over. Back to work.
References
- Fowler, D. W., and Sullivan, R. M. 2011. The first giant titanosaurian sauropod from the Upper Cretaceous of North America. Acta Palaeontologica Polonica, 56, 685-690.
- Witton, M. P., and 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, e13982.