Re: Feducciary challenges

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

> From an anonymous Feducciary/ABSRDist (by way of Ken Kinman):

> A duck-sized, presumably diurnal dinosaur like this one
> would almost certainly not need insulation.

How can this personage presume that all small theropods were diurnal?  If 
their prey of choice were small mammals, it is quite possible that such 
predators were crepuscular or nocturnal.  Okay, so the days were hot and 
steamy, but nights may have been a little on the chilly side.  That feathery 
coat and pair of "leg-warmers" may have come in handy!

I've also suggested before on this list that in some theropods (at least) 
the feathery coat (or "pre-feathers"/"dino-fuzz") may have been ontogenetic 
and/or seasonal.  Juvenile tyrannosaurs may have hatched from an egg all 
warm and fuzzy, with a coating of natal down, but lost it by the time they 
reached maturity.  Other species, which had smaller adult body sizes, may 
have retained such a coat throughout life, and supplemented it with other 
types of feathers - such as more elongated and differentiated feathers 
developed for non-insulatory purposes: aerial locomotion, display, brooding.

In small theropods (and perhaps large theropods too, depending on geography) 
feathery coats may also have been seasonal - sprouted with the approach of 
cooler weather, and shed at the onset of warmer temps.  This would explain 
the absence of downy structures in _Compsognathus_ and its presence in its 
close relative _Sinosauropteryx_.  (Of course, _Compsognathus_'s nakedness 
may also be attributable to preservational or preparational artifacts; but 
it is worth considering that the apparent absence of integumental structures 
from the Solnhofen _Compsognathus_ might actually be real.)

Rampant speculation, I know.  Corroboration of ontogenetic changes in 
integument would require a growth series of a single species to be preserved 
with these structures intact.  Maybe we could determine this for 
_Confuciusornis_, but (so far) not for any nonavian theropod.  Seasonal 
shedding would be downright impossible to prove considering the vagaries of 
the fossil record.


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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