Prosauropod monophyly ...

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

My two cents on the prosauropod monophyly thing:

Prosauropod material is notoriously scrappy (except of course for 
Plateosaurus and some other odds and ends), the body form or bauplan of 
prosauropods is relatively homogenous (perhaps in relation to their Pangean 
distribution?), and I know of no one who has resolved whether prosauropods 
are mono- or paraphyletic with any degree of certainty.

Many prosauropods strike me as "herbivorous theropods" (I know, perish the 
thought), and while their long necks and small heads may indicate a 
relationship to sauropods, if there was one it seems to me (read opinion 
here) that both groups diverged very early (and not a very original opinion: 
Charig et al., 1965).  And by "herbivorous theropods" I don't mean that 
literally, only that the two groups appear to share more in common with each 
other than either does with sauropods. Which is good, because we wouldn't 
want the majesty of sauropods tainted with theropod blood ...

I know, I know, the big thumb claw in prosauropods is always touted as a 
link between them and the sauropods, but the shape and articulations in the 
two groups are very different.  Prosauropods can swing their thumb claws 
medially and flex and extend them quite nicely.  Sauropods can flex their 
claws somewhat, but extension or abduction of the thumb claw (away from the 
substrate) is impossible unless you disarticulate the phalanges.  So much 
for sauropods "elevating" their thumb claws above the ground. =)  Hey, I had 
to throw that in somewhere! =)

Too busy to write much,
Matt Bonnan
NIU



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