Re: Alvarezsaur Polarity and Features

[Nick Longrich <longrich@alumni.princeton.edu>]

>   Finally, in regards to the arms used for myrmecophagy, there is 
> little else that these arms
> could do but dig (see Nick Longrich's abstract in the 2000 JVP 
> abstract volume, 20(suppl. to 3)).
> It is unlikely that such powerful limbs were adapted for grasping 
> based on the form of the manus
> having a distinct form related to fossorial earth-moving. No other 
> hypothesis satisfies the
> function of the arms, despite the leggedness of the animal. It 
> simply appears to be an ecology
> (cursorial myrmecophage) not encountered before: we have arboreal, 
> small and large subcursorial,

	Yeah- the way I view it, all the other myrmecophages are 
basically quadrupedal. The forelimbs in a mound-cracking myrmecophage 
tend to be "geared down" to produce lots of force at the expense of 
speed. Basically, opening nests pulls you one way (high force, low 
speed) which conflicts with being highly cursorial (high speed). Its 
not that diggers can't run (armadillos can move pretty fast 
considering their build) but I don't think you'd ever see an animal 
which is both highly cursorial and highly fossorial in a quadruped. 
In a *biped*, however, the forelimbs can do whatever the heck they 
want- act as picks, paddles, meathooks, wings, whatever- and it has 
much, much less effect on the hindlimbs. So you can get away with 
fossorial forelimbs (geared down for force), and cursorial hindlimbs 
(geared up for speed). In contrast, most myrmecophages defend 
themselves either by burrowing, climbing trees, and/or with armor, 
probably since slow, powerful forelimbs don't preclude these in a 
quadruped. As for how short the arm is- well, I don't see why it 
couldn't either crouch down on top of a mound, or stick its chest 
right up against one, to dig in. It couldn't get more than a few 
inches in, and it would have to back up to stick in nose in, but I 
don't see these as major obstacles. Otherwise, the shorter your 
limbs, the more force they can generate, so the better they are as 
digging tools.
	But I don't pretend to have the final answer, and an 
alternative hypothesis has been proposed: Anton Wroblewski 
(Wroblewski, A. 1998. Cocktail Napkin, 1 pp). once drew a picture of 
a Mononykus using its claw to open the pop-tab on a beer. I imagine 
the long nose could be inserted easily into a can/bottle. Beer of 
course is high in complex carbohydrates, good for the heart, and, 
recent studies suggest, may increase IQ by improving blood flow to 
the brain (which is why so many paleontologists are so smart). Salted 
nuts may have been required to add protein to their diet and to 
maintain ion balance.
	Maybe I could get Budweiser to sponsor an expedition to the 
Gobi to look for old cans and bottles as evidence for this 
hypothesis...