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RE: tiny-armed theropods



Mike Taylor wrote:

<Earlier you said "I believe the prevailing theory is that limb reduction 
occurred as the head become enlarged (in tyrannosaurs), such that the head is 
the primary tool for acquiring prey."

If that is the theory then it plainly doesn't work for taxa whose heads didn't 
become enlarged.>

  This is true, I did say that, and the operational theory doesn'nt necessarily 
account for what appear to be relatively smaller heads in abelisaurids, 
compared to tyrannosaurs! It is certainly not the case when considering the 
large skulls of carcharodontosaurs, which manage to make due with relatively 
long, but very narrow and robust skulls and yet retaining large forelimbs with 
a prehensive quality to them (large unguals and the like). It would, in fact, 
render the issue difficult to resolve were we to find a really large head for 
*Megaraptor namunquaihuii*, but that is exactly what I would expect to find 
based on comparisons with close taxa.

  I offered an alternative viewpoint, one in which takes the likelihood of 
behavior based on functional morphology into account.

  Elsewhere, someone asked about tyrannosaur development with tiny arms:

  Several juvenile tyrannosaurs (as I note in my various posts on 
tyrannosauroids, available here: 
http://qilong.wordpress.com/tag/tyrannosauroids/ ) have extremely short arms, 
indication reduction of the limbs is not directly correlated with growth of the 
skull into immense proportions, which belies the functional use of the skull as 
an adult-based acquisitor; indeed, juveniles would have just as much of a 
problem doing what adults were (or were not) doing with their arms, and the 
alternative option is more selective prey options which can be hand-manipulated 
[sorry, redundant], however unlikely. 

Cheers,

  Jaime A. Headden
  The Bite Stuff (site v2)
  http://qilong.wordpress.com/

"Innocent, unbiased observation is a myth." --- P.B. Medawar (1969)


"Ever since man first left his cave and met a stranger with a
different language and a new way of looking at things, the human race
has had a dream: to kill him, so we don't have to learn his language or
his new way of looking at things." --- Zapp Brannigan (Beast With a Billion 
Backs)