Re: Triassic dinosaur evolution

[Mark Witton <Mark.Witton@port.ac.uk>]

I really, really don't have time to write this, but the heads of allosaurs, 
dromaeosaurs and a bunch of other 'saurs ain't build for holding struggling 
animals. They may get there first, but theropod arms are surely going to be 
holding things in place while sickle claws, raking jaws or whatever do the 
dirty work. Noteable exceptions to this, of course, as tyrannosaurs, which 
appear to have jaws that both hold and dispatch prey. Maybe that's why their 
arms were comparatively diminutive. 

Right, that's all I'm contributing to this. Must... finish... thesis...

Back to work.

Mark

--

Mark Witton

Palaeobiology Research Group
School of Earth and Environmental Sciences
University of Portsmouth
Burnaby Building
Burnaby Road
Portsmouth
PO1 3QL

Tel: (44)2392 842418
E-mail: Mark.Witton@port.ac.uk 

>>> Michael Habib <mhabib5@jhmi.edu> 17/09/2008 14:53 >>>
> Then could someone please pass this on to all the paleo artists out 
> there? I've grown so tired of seeing drawings of theropods with 
> completely serviceable forelimbs, just tucking them away like they 
> were just featherless, non-functional wings.

Fair enough, but what counts as "serviceable"?  If you're thinking of 
maniraptorans, then I absolutely agree.  However, there is a strange 
pattern that many (if not most) non-maniraptoran theropods with robust 
forelimbs still can't reach out in front of their mouths, making the 
forelimbs rather unavailable in prey capture.  Allosaurids, for 
example, have robust, powerful arms - but the length is still quite 
short in comparison to the total length of the cervical series and 
head, so the jaws would contact food well before the arms ever got 
close.  That doesn't make the forelimbs useless, but it appears to make 
them rather unimportant for prey acquisition.

Cheers,

--Mike H.


Michael Habib, M.S.
PhD. Candidate
Center for Functional Anatomy and Evolution
Johns Hopkins School of Medicine
1830 E. Monument Street
Baltimore, MD 21205
(443) 280 0181
habib@jhmi.edu