Re: dino-lice

[Tim Williams <tijawi@gmail.com>]

Augusto Haro <augustoharo@gmail.com> wrote:

> So, if non-avian
> theropods grasped prey with their hands, they likely did in a much
> different way from both carnivoramorphans and birds of prey.
> Third, the common recurrence of forelimb reduction among predatory
> theropod dinosaurs, even some deinonychosaurs, suggests the forelimbs
> were not much important in predation.


I agree.  But I'm not sure what you're driving at here.  The earliest
known alvarezsaur (_Haplocheirus_) has a grasping, trenchant,
functionally tridactyl manus.  This was the template from which the
truncated, functionally monodactyl forelimbs of derived alvarezsaurs
evolved from.


I certainly agree that even in many predatory theropods, the forelimbs
had limited utility in prey seizure.  Even a carnosaur like
_Acrocanthosaurus_, with relatively long and powerful forelimbs, had
limited anterior reach, and probably attacked prey initially with its
jaws (Senter & Robins, 2005).  The forelimbs then swung into action to
secure and dispatch the prey.


Forelimb reduction among many non-avian theropods indicates not only a
reduced role in predation (minor role in tyrannosaurids, none at all
in carnotaurines), but in certain non-predatory lineages the forelimbs
took on other roles.  For example, bringing branches to the mouth
(ornithomimosaurs, perhaps therizinosaurs - although the huge
forelimbs of _Therizinosaurus_ look to me to be defensive weapons);
tree-climbing (scansoriopterygids, perhaps _Yixiansaurus_); and flight
(birds).




Cheers
Tim