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Early sauropods not just name changes WAS Re: Antentonitirus pro-nun-see-a-shun?



In response to Mickey's statement:

"Not that I'm against using this definition of Sauropoda, but people have to realize it's more of a change in taxonomy than knowledge that's giving us so many early/basal sauropods."

And Tim's:

?A good point. _Blikanasaurus_, _Melanorosaurus_ and _Anchisaurus_ have not suddenly become more "sauropod-like". As Mickey said, what's happened is that the name "Sauropoda" has slid further down the sauropodomorph tree, pulled there by the reorganization of basal sauropodomorphs. By dint of its stem-based definition, the composition of Sauropoda is at the mercy of _Plateosaurus_ and its relative position in sauropodomorph phylogeny.?

All well and good, but there is more to this than simple taxonomic name shifting. This is a conceptual change of what it means to be a sauropod, and the re-examination of these ?prosauropods? is an important step in trying to understand the evolutionary transformations that sauropods underwent.

I realize that it has never been this black-and-white, but if one considers Prosauropoda to be a monophyletic group that, beyond sharing a coming ancestor with Sauropoda, had little to do with their evolution, then one is left without much to go on for sauropod origins. However, with previous ?prosauropods? being included or considered as basal sauropods, we have a chance to test hypotheses regarding the evolution of various sauropod features of the skeleton.

Furthermore, the evolution of the limb skeleton in sauropods is an important but often undervalued source of potential data for the question, ?How?d they get so big?? Even if a more ?gradist? view of Prosauropods to Sauropods is later shown to be incorrect or in need of modification, I think it is more than taxonomic name shifting to re-consider the implications of the prosauropod limb skeleton for sauropod gigantism.

For someone who is not a systematist, these changes in phylogenetic interpretation lead to a whole new series of functional ramifications. Call them whatever you like, and argue about what they should be called, but what Yates, Kitching, and some others have been doing is prodding the rest of us into re-evaluating the beginnings of the largest dinosaur giants, and that to me is what is most significant about this recent announcement.

Matt


Matthew F. Bonnan, Ph.D. Department of Biological Sciences Western Illinois University Macomb, IL 61455 (309) 298-2155 mbonnan@hotmail.com MF-Bonnan@wiu.edu http://www.wiu.edu/users/mfb100/

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