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RE: Feathering in coelurosaurs



> From: owner-dinosaur@usc.edu [mailto:owner-dinosaur@usc.edu]On Behalf Of
> Mary Nalasco
> Sent: Monday, April 03, 2000 9:06 PM
> To: DINOSAUR@usc.edu
> Subject: Re: Feathering in coelurosaurs
>
>
> It seems probable to me that baby tyrannosaurs had feathers, but I'm
> wondering about adults of small species like Alioramus, who are
> no bigger or
> even smaller than some coelurosaurs of other groups, like
> Utahraptor. Is it
> a question of metabolism, perhaps? Can more evolved coelurosaurs manage
> feathers better?

Whoa there...

Okay, let's take things one step at a time:
1) We do not as yet have direct confirmation of
feathers/protofeathers/DESE/whatever you want to call them in
tyrannosaurids.  They are inferred to be present in tyrant dinosaurs by the
same reason we infer feathers being present in _Hesperornis_: tyrannosaurids
are bracketed phylogenetically by creatures observed to have
feathers/protofeathers/whatever (maniraptorans on one side,
_Sinosauropteryx_ on the other).
2) Based merely on phylogeny, the expectation would be that even _T. rex_
was covered by this stuff.  However, alternative speculation (by analogy to
some large bodied tropical epithere mammals such as elephants and white
rhinos) suggests that large adult tyrannosaurids may have a reduced plumage:
at larger body sizes in warmer regions, insulation is not as important.
However, this is *simply speculation*.
3) So, what of small adult tyrant dinosaurs?  Who can say?  It is simply
speculation to think that larger tyrant dinos might lack
feathers/protofeathers; one might argue that a 250 kg adult might still need
more insulation than a 2500 kg one.

Note that even step 2 isn't as strong as it could be: there have been large
bodied (comparable in size to tyrant dinosaurs) mammals in the tropics with
LOTS of fur: giant ground sloths being the main one.

So it is possible that an adult _Alioramus_ might have had more fuzz than an
adult _Tyrannosaurus_; however, we are currently lacking data by which to
test this hypothesis.

Hope this helps.

                Thomas R. Holtz, Jr.
                Vertebrate Paleontologist
Department of Geology           Director, Earth, Life & Time Program
University of Maryland          College Park Scholars
                College Park, MD  20742
http://www.geol.umd.edu/~tholtz/tholtz.htm
http://www.geol.umd.edu/~jmerck/eltsite
Phone:  301-405-4084    Email:  tholtz@geol.umd.edu
Fax (Geol):  301-314-9661       Fax (CPS-ELT): 301-314-7843