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Re: Hanson 2006, Mortimer, Baeker response

Tim Williams wrote-

_Tendaguria_ could be a highly aberrant basal titanosaurian - if (and I mean IF) it is the same as _Janenschia_. Bonaparte et al. (2000) split the _Janenschia_ material three ways: limb bones (retained in _Janenschia_); presacral vertebrae (assigned to a new sauropod, named _Tendaguria_); and caudal vertebrae (unnamed). But the limb bones and presacral vertebrae both come from a VERY heavily built sauropod; the caudals are strongly procoelous; and the limb bones also show titanosaur characters. The dorsals of _Tendaguria_ are just plain weird (puny neural spines, massive transverse processes), and this makes _Tendaguria_ hard to place. If _Janenschia_ and _Tendaguria_ prove to be the same after all, then this sauropod is a titanosaur with highly autapomorphic dorsals.

Tendaguria seems to have gotten its own family largely because Bonaparte was being more phyletic than cladistic. The dorsals were different enough from Saltasaurus that he figured it deserved to be separated. But he said the same thing about Malawisaurus. The general morphology of the dorsals looks more similar to titanosaurs than other sauropods, and I wouldn't be surprised to see it as a titanosaur in a cladistic analysis.

As for _Agustinia_, the problem here is that this sauropod is too poorly known to confidently ascertain its relationships. The presence of body armor suggest titanosaur affinities, but I admit this doesn't seal the deal.

New material has been found (used in Curry Rogers' thesis' analysis) and shows it was a titanosaur.

In regard to the theme of this thread, finding 'new' categories of dinosaurs is impossible in a way. At least in the sense of broad groups like Sauropoda. After all, Dinosauria is defined to only include Saurischia and Ornithischia. So any dinosaur has to fall into those clades. Saurischia is defined to only include Sauropodomorpha and Theropoda, so again, any saurischian will be one of those. A sauropodomorph is either going to be a prosauropod, a sauropod, or more basal (like Saturnalia, Thecodontosaurus, etc.). And similar statements could be made for any dinosaur group. Our current knowledge and phylogenetic taxonomy give us a well-supported backbone, and all that's left is to fill in the gaps. But that's how it is with any clade of organisms whose phylogeny is well known. And the gaps are sometimes huge. So there's still plenty of work to do.

Mickey Mortimer