Re: Do not misunderestimate the king was Re: Evolution of tyrannosauroid

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

Michael Habib writes: 

> The one thing that can be 
> said for certain is that the forelimbs were placed under substantial 
> loads.  That, in itself, is very intriguing.  I remain skeptical that this 
> clinches a particular feeding dynamic for a number of reasons, but the 
> information is quite informative, regardless.

I'm skeptical that *adult* tyrannosaur forelimbs were used to capture or 
manipulate prey at all. It wouldn't matter how strong the arm muscles 
themselves were if the shoulder joints weren't up to withstanding the forces 
generated by struggling multi-tonne prey. If I were an adult tyrannosaur, 
I'd rather use my massive jaw and neck muscles to subdue prey - or use a 
'bite and retreat' method and not attempt to hold onto prey at all. 

I've always thought that tyrannosaurs may have outgrown their forelimbs as 
far as predatory behaviour went, using them extensively as juveniles (when 
the forelimbs were relatively larger), and using them less (or not at all) 
as adults, once bite strength was sufficient in itself to kill prey. 

Perhaps the main use adult tyrannosaurs had for their forelimbs was to help 
them rise from a crouching position? If they used their pubic boot as a 
pivot point, they could have rocked forward while straightening their legs 
beneath them, and dug their forelimbs into the ground to prevent the animal 
scooting forward on its chest. Once the legs had straightened enough, the 
feet would have become the new pivot point. By throwing the head and neck 
back over their shoulders (perhaps thrusting back with the forelimbs at the 
same time) and lowering their tail, they could then have rocked back into a 
standing posture. Such use of the forelimbs might result in the stress 
fractures and muscle avulsions of the humerus that have been observed - with 
no predatory role for the forelimbs required. 

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Dann Pigdon
GIS / Archaeologist              geo cities.com/dannsdinosaurs
Melbourne, Australia             heretichides.soffiles.com
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