shortweird was Isisaurus?
August 13, 2009
Back in 1999 or 2000 Jaime Headden sent me his skeletal reconstruction of what was then known as Titanosaurus colberti (Jain and Bandyopadhyay 1997), but which has recently been renamed Isisaurus colberti by Upchurch and Wilson (2004). Jaime’s skeletal reconstruction and life restoration are here. Somebody threw a skin over the recon to produce this life restoration.
As you can see, the sauropod as reconstructed by Jaime is weird as heck.
I tried my own, and it came out quite a bit differently, but also weird as heck. I have to give a lot of the credit to Jaime; my recon is basically his, traced, with some of the elements scaled differently.
DO NOT assume that this is accurate. IIRC, Jaime scaled the elements in his recon using the scale bars in the figures from Jain and Bandyopadhyay (1997), and I scaled mine using the measurements given in the text. As you can see if you compare to the two recons, those sources of data do not agree (hmm…where have we seen this problem before?). Also, the whole skeleton of Isisaurus is not known so a lot of what you see here is guesswork. Finally, I drew this on a spare afternoon almost a decade ago, and I haven’t ever done a single thing with it that would give me any real-world feedback to tell me just how screwed up it is. Looking at it now, the limb bones look awfully long for those girdles, the anterior caudals don’t look very much like the anterior caudals of anything, and…yeah. I could barely muster the courage to post it. But I am posting it, partly because it is an artifact of my own intellectual ontogeny, partly to spark discussion, and partly to highlight the following problem:
We’ve got two weird and conflicting reconstructions, based on two conflicting sets of measurements from the same paper!
So what now? I’ve always intended to update this. I would make a start by scanning all of the elements from Jain and Bandyopadhyay (1997) and saving them as separate layers in Photoshop or GIMP. Then each element can be rescaled at will. And I’d build a background grid to hopefully help keep the scaling honest, like I did with my Brachiosaurus and Sauroposeidon skeletal recons. And I’d probably try plugging the Isisaurus elements into Mark Hallett’s Rapetosaurus skeletal reconstruction; back when Jaime and I were working on our drawings no one had ever found a reasonably complete titanosaur so we were both working a bit in the dark.
All that would possibly make for better versions of these drawings, but the fundamental difference is in the measurements, and those aren’t going to change until someone measures the skeleton again to check whether the scale bars or the published measurements are accurate. My guess is that the published measurements are accurate, or at least a lot more accurate than the scale bars. Scale bars are notoriously difficult to get right, but it is hard to creatively misuse a tape measure. Still, for now, we just don’t know.
We know that Isisaurus must have been pretty darn weird because its cervicals are so short. I tend to spend most of my time thinking about critters like Sauroposeidon and Erketu and Mamenchisaurus youngi, in which the cervical centra can be six times as long as tall or even longer. Isisaurus went the opposite direction–its cervical centra are only about twice as long as tall, right down the column. The only other sauropods with such short cervicals are dicraeosaurids such as Brachytrachelopan. Given the other examples of homoplasy between diplodocoids and titanosaurs, I wonder if Isisaurus and Brachytrachelopan were ecological analogues, and I wonder what they were up to.
- Jain, S.L., and Bandyopadhyay, S. 1997. New titanosaurid (Dinosauria: Sauropoda) from the Late Cretaceous of central India. Journal of Vertebrate Paleontology 17:114–136.
- Wilson, J.A., and Upchurch, P.2003. A revision of Titanosaurus Lydekker (Dinosauria– Sauropoda), the first dinosaur genus with a ‘Gondwanan’ distribution. Journal of Systematic Palaeontology 1: 125–160.