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2011/4/23 Tim Williams <firstname.lastname@example.org>:
> In any case, your question may well be inapt because (aside from
> birds) most extant vertebrates are quadrupeds of some description.
Well, the carnivores which more manipulate their prey with the
forelimbs are mammalian, and mammalian carnivores are mostly
> Late Cretaceous alvarezsaurids evolved from bipeds that used their
> hands for predation (i.e., a trophic function), not for locomotion.
I know I will not be much popular by saying this, but am not sure of
this... First, no support from EPB. Second, theropods lost digits,
even in taxa with recurved unguals as herrerasaurids. Looking at
modern carnivores which manipulate prey, they tend to be pentadactyl
and show digits more or less similar in size. Indeed, it is in
carnivores which manipulate prey the less (cursorial canids and
hyenids), that the manus loss more digits (ok., just the pollex). So,
I would not say that lack of digital number reduction in mammals has
to do with some need about locomotion. Neither do we see among modern
carnivores anything similar to the digital elongation present in
theropods as Herrerasaurus or deynonychosaurs, as well as other
theropods. Although not forelimbs, the grasping pes of birds of prey
do not resemble the non-avian theropod mani either. 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.