Re: Major new paper on dromaeosaurids, with other significant maniraptoran info

[Tim Williams <twilliams_alpha@hotmail.com>]

>    In the history of life on Earth, relatively few predators have required 
> grasping hands with opposable thumbs for catching prey.


True.  But... in the history of life on Earth, relatively few predators are 
bipeds.  Predatory mammals are quadrupeds, in which the forelimbs are also 
used for locomotion.  The first dinosaurs were bipeds, which 'freed-up' the 
forelimbs for use in predation: siezing, holding and processing prey.

Predatory birds often have a pes designed for grasping.  Of course, there 
are exceptions: the secretary bird simply pins prey to the ground with its 
feet.

>    If groups of _Deinonychus_ did indeed hunt larger prey -- 
> _Tenontosaurus_, apparently -- it is entirely possible that these 
> dromaeosaurs were unique in these aspects of their hunting style.


I agree with this 100%.  The two-handed grasping method proposed for 
_Deinonychus_ seems perfect for catching and holding large prey.  I am just 
not convinced that small maniraptorans like _Microraptor_ and 
_Archaeopteryx_ used their arms in the same manner.

>    Certainly dromaeosaurs could have hooked and snatched up small prey in 
> one hand with ease, or they could have slapped their clawed hands onto 
> small prey items prior to delivering killing bites.

I'm not certain that hooking and snatching prey was as easy as you make it 
out to be, given the length and relative immobility of the fingers, and the 
altered range of motion of the manus courtesy of the 'swivel-wrist'.  
Maniraptorans made some big changes to the architecture of the distal 
forelimbs, and none of them helped in their ability to grasp and manipulate 
small prey.  Quite the opposite, in fact.

>  Most predators today don't even use their forelimbs to catch their prey,

By and large, modern reptilian and mammalian predators are quadrupeds.  As 
for modern birds... their options are much more limited.

>    Two handed scooping doesn't sound far fetched to me, as either hand 
> will snag the intended food item and quickly clap toward the opposing hand 
> before the animal has a chance to get away.  Dromaeosaurs certainly had 
> long forelimbs, and I would expect they were good for something (aside from 
> flying and/or gliding in the smaller varieties).  What aspect of this two 
> handed scooping scenario troubles you?

Sure, a two-handed grasping motion might work for snagging and holding prey. 
 But what was wrong with the grasping and raking manus present in early 
theropods? The primitive theropod manus was specialized for handling prey.  
Maniraptorans diverged from this condition.



Tim

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