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Re: tiny-armed theropods



This notion is a lot easier to swallow for big-headed tyrannosaurs
than for little-headed abelisaurs.

-- Mike.



On 5 October 2011 08:56, Jaime Headden <qi_leong@hotmail.com> wrote:
>
>   I believe the prevailing theory (and Tom Holtz can correct me on this) is 
> that limb reduction occurred as the head become enlarged (in tyrannosaurs), 
> such that the head is the primary tool for acquiring prey. This is emphasized 
> in enlarged neck and shoulder bones, more robust ribs, and a skull with more 
> intricate interlocking connections or bony stops (or fusion), which is 
> designed to reduce the stresses borne between bones when the skull is being 
> used so heavily. On top of this, it has been theorized that abelisaurids, 
> specifically *Carnotaurus*, used the head in disabling prey while at speed 
> (Bakker and Paul have somewhat romanticized this with "slash and run" 
> attacks, although the "strike and strip a chunk of flesh off" idea that was 
> illustrated by Paul in _Predatory Dinosaurs of the World_ emphasizes a more 
> stationary strategy). Tyrannosaurs, on the other hand, seemed suited to 
> ambush attacks, literally ramming their jaws into the flanks or whatever of 
> the animal and doing a considerable amount of damage while restraining the 
> prey.
>
>   This is contrasted with smaller theropods or raptorial birds, in which the 
> limbs are the primary acquisitors, and the jaws are designed to deliver more 
> delicate attacks, or just to process flesh; in allosaurs at least, as in 
> abelisaurs, the teeth are very slender and much more suited to being drawn 
> through the flesh than in being rammed at high speed into the side of 
> whatever.
>
>   So the short and skinny is that these animals were favoring use of the 
> cranium and jaws to handle and hold prey, rather than the limbs, and this may 
> have been predicated on the ambush, guerrilla strategy rather than a "hit and 
> run" type attack.
>
> 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)
>
>
> ----------------------------------------
>> Date: Wed, 5 Oct 2011 03:47:22 -0400
>> From: hammeris1@att.net
>> To: DINOSAUR@usc.edu
>> Subject: tiny-armed theropods
>>
>> Has anyone given any thought and proposed ideas why tyrannosaurs
>> (north) and abelisaurids (south) developed their tiny arms on two
>> seperate unconnected land masses - as in, what forces drove this to
>> happen?
>> Is it just coincidence that they were both around at (generally) the
>> same time-frame?
>>
>> Brian
>>
>
>
>