[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index][Subject Index][Author Index]
On 4/21/2011 11:30 PM, Tim Williams wrote:
Jason Brougham<firstname.lastname@example.org> wrote:
In other words, how small would the arms have to be before we could all agree
that they couldn't be used for scratch digging? Right now we all agree Shuvuuia
would have to practically press its chest
against anything it touched with its arms, and that it couldn't see what its
arms were doing. Yet the bone shapes, alone, convince many that it was digging
with the arms.
I'm convinced that the forelimbs of alvarezsaurids were used for
*something*, and that *something* was associated with diet.
As anyone who has done any digging knows, teeny little arms poking out
of your chest are NOT the tools you need, as Jason and several others
point out, especially when range of movement is limited.
OTOH, it is consensus that the anatomy shows the presence of significant
physical stresses while alive.
Those who have crawled around in tight places in caves or culverts can
readily imagine that teeny but powerful arms poking out of your chest
could be very useful indeed -- especially when backing out of a
constricted or dead-end passage, where the hind limbs are nearly useless
or even a hindrance.
With a nod to Pigdon and the "Cloaca Speculation" -- assigning these
short but strong limbs a locomotive function that involves assisting the
narrow head and neck in accessing and retreating from burrows, hives,
nests, hollow logs and/or the nooks and crannies of large animal
carcasses while in search of insects, small animals, or even small eggs
is the best speculative fit in my view to the general morphology of
Also, the locomotive function offers a clear path of incremental
evolution from the basal Haplocheirus to the highly derived Shuvuuia....