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

["Matthew Bonnan" <mbonnan@hotmail.com>]

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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