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I have always assumed that deinonychosaur limbs were used together, rather like
a pair of ice tongs, to grasp objects held between them. Am I correct that in
life their hands would have faced each other rather than being held "palm
downwards" as in many restorations, and that they could have been brought
together at the midline?
1825 Shady Creek Court
Canada L5L 3W2
On 2011-04-25, at 1:00 PM, Tim Williams <email@example.com> wrote:
> Jason Brougham <firstname.lastname@example.org> wrote:
>> Senter (2006) found that the second finger in Dromaeosaurs was so flexible
>> that Deinonychus could stab itself in the palm with its claw (Fig. 3 C).
>> The first ungual could flex at 88 degrees to the phalanx! Gishlick (2001)
>> found about the same thing.
>> Thus, the literature shows extremely developed grasping ability in
> I'm not arguing that individual fingers were incapable of an
> impressive amount of flexion; clearly they were. However, what I am
> saying is that as a unit, the manus was not very useful for grasping
> small prey. This inability is standard for theropods - and the
> elongation of the fingers, combined with the altered range of motion
> proscribed by the semilunate carpal joint, constrained the grasping
> ability of the maniraptoran manus even further. The manus had no
> one-handed prehensile ability, and (with the exception of
> _Bambiraptor_) could only capture prey in a two-handed fashion.
> Gishlick and Senter both came to the conclusion that _Deinonychus_
> could not grasp an object with one hand - unless that object was
> pressed by the manus against its chest. _Bambiraptor_ was
> reconstructed by Senter as having an opposable manus - but he also
> made it clear that this morphology was apparently unique among
> theropods. Typically in theropods, the fingers diverged too much
> during flexion to have been capable of enclosing a small object. So
> in order to capture small terrestrial prey, _Deinonychus_ would have
> had to scoop an object up with both hands. In _Deinonychus_, as with
> any other maniraptoran, feathered forelimbs would have made this
> _Deinonychus_ would have no difficulty grasping large prey, because
> the forelimbs would have grasped the prey in a two-handed fashion.
>> This feature is actually what the group was named after.
> Maniraptorans were named after a raptorial manus; yes, I know.
> Nevertheless, among non-avian maniraptorans, hypercarnivorous
> predators such as _Deinonychus_ and _Velociraptor_ may have been the
> exception in terms of carnivorous habits. Many maniraptorans were
> likely herbivores (or at least omnivores), including oviraptorosaurs,
> therizinosaurs, scansoriopterygids, and basal troodontids - all of
> which had a maniraptoran manus. So the correlation between predatory
> ability and the presence of a maniraptoran-style "raptorial" manus is
> not especially tight. Alvarezsaurs, as discussed at length on this
> thread, departed radically from this forelimb morphology.
> Check out Zanno & Makovicky (2010) for the recurrence of
> herbivorous/omnivorous adaptations among theropods in general, and
> maniraptoriforms in particular.