Re: Naked theropods (was RE: Phil Currie celebration, tyrant skin, and other things)

["Tim Williams" <twilliams_alpha@hotmail.com>]

"Jura" wrote:

> But, if the feathers started off on tracts, then the possiblity of these
> two >coexisting is greater, though it still begs the question of why all
> extant birds >have bare skin between their tracts and not scales, if there
> was no reason to >lose them (and yes I don't think that weight would be the
> problem as scales >aren't that heavy to begin with, certainly not small
> ones).

I would say weight reduction might very well have been a reason for
discarding body scales.  After all, they were not really needed any more
(except on the face and feet, which were probably protected by rather
different scales to the rest of the body).  Sure, a single scale doesn't
weigh very much, but all those little scales add up.

An analogous example might be teeth.  Most birds in the Cretaceous (at least
for which skull material is known) had teeth, although one might consider
that teeth are quite heavy for their size and would be dispensed early on in
avian evolution.  They were lost by certain Mesozoic lineages, including
Neornithes, *perhaps* for weight reduction.  It may have been the same for
scales.


Tim

------------------------------------------------------------

Timothy J. Williams

USDA/ARS Researcher
Agronomy Hall
Iowa State University
Ames IA 50014

Phone: 515 294 9233
Fax:   515 294 3163

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