Re: Theropod Forelimb Reduction

[Dann Pigdon <dannj@alphalink.com.au>]

On Wed, Oct 21st, 2009 at 12:15 PM, "Thomas R. Holtz, Jr." <tholtz@umd.edu> 
wrote:

> Given that Raptorex was only approximately 3 m long as an adult and has
> highly reduced forelimbs, while larger more primitive tyrannosauroids
> (Eotyrannus, Guanlong, etc.) have proportionately longer forelimbs, the
> new guy actually throws a monkey wrench into this idea. If the reduced
> arms of Raptorex represent the same reduction present in Tyrannosauridae,
> then it evolved in small body size.
> 
> Indeed, the presence of large theropods with big forelimbs (Gigantoraptor,
> Therizinosaurus, Deinocheirus, etc.) shows that it is possible to be long
> armed and big at the same time.

Raptorex had the characteristic 'D-shaped' teeth (in cross section, that is) 
seen in later 
tyrannosaurs. Could it be that a move away from relatively fragile, narrow, 
blade-like teeth 
towards something more capable of withstanding lateral movement meant that the 
jaws took over 
some (or even most) of the role previously played by the forelimbs during prey 
capture?

-- 
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Dann Pigdon
GIS / Archaeologist                Australian Dinosaurs
Melbourne, Australia               http://home.alphalink.com.au/~dannj
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