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Re: alverezsaurs (was dino-lice)

While it is surely unlikely that the forelimb was not simply a display 
structure, this does not mean that it was not the result of sexual selection 
(either for fighting rivals or grappling during copulation)?  If that is the 
case I suspect that it is highly unlikely that we will ever discover how it was 
used, as the use may simply not have been analogous with any structure on a 
living animal.

 Ronald Orenstein
1825 Shady Creek Court
Mississauga, ON L5L 3W2

----- Original Message ----
From: Tim Williams <tijawi@gmail.com>
To: dinosaur@usc.edu
Sent: Thu, April 21, 2011 12:52:22 PM
Subject: Re: dino-lice

Vivian Allen <mrvivianallen@googlemail.com> wrote:

> I think we can agree Jason has made Shuuvia and
> Mononykus exerting large forces with their pectoral limbs sound pretty
> difficult.

Speaking for myself, I don't agree at all.  I'm not doubting the
efficacy of Senter's biomechanical work, which posited that the
forelimbs of _Mononykus_ are suited for scratch-digging or
hook-and-pull movements.  What I'm skeptical about is whether
_Mononykus_ (or any other alvarezsaur) deployed the forelimbs as part
of a specialized ant- or termite-eating ecology - specifically,
targeting insect nests or insect-infested wood.  It doesn't mesh with
the remaining proportions of the alvarezsaur postcranium; it requires
a highly cursorial animal with an elevated metabolism to subsist on a
low-calorific diet; and the anteater/vermilinguan analogy is not
especially compelling considering that these extant mammals have long
forelimbs capable of a wide range of motions.

I agree with GSP that the pectoral musculature is way over-the-top for
just an ornamental structure.  Plus, the manus retained a single large
claw - what was it there for if the forelimb was used only for
display?  There is no indication of atrophy of the alvarezsaur
forelimb - just heavy-duty truncation.