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> From: owner-dinosaur@usc.edu [mailto:owner-dinosaur@usc.edu]On Behalf Of
> Ken Kinman
>      Being such big animals, the only way I can imagine adult
> tyrannosaurs
> have a thick coating of protofeathers would be if they lived in a cold
> climate (like woolly mammoths did).

While in general I would agree with this, but I do want to remind people
that giant ground sloths included bear-to-elephant sized animals that lived
in a wide variety of environments, including the tropics, and as far as we
know they were all very hairy.  For that matter, bears from paleotropical
and neotropical rainforests can be quite hairy.

Please note, though: that was just a reminder, and not an excuse to start
drawing shaggy rexes! :-)

> From: owner-dinosaur@usc.edu [mailto:owner-dinosaur@usc.edu]On Behalf Of
Michael Lovejoy
> So, can I have everyone's arguments for (or against!) big tyrannosaurs
having feathers.

The primary argument "for" is phylogenetic.  Tyrannosauroids, in at least
some analyses, are nested within the clade comprised of _Sinosauropteryx_
(known to have simple branching integumentary elements) and maniraptorans
(known to have full-formed feathers).  Assuming the homology of the two
integumentary structures, the simplest explanation for the evolution of this
feature is that it evolved a single time in dinosaur history, and that it
was present in the common ancestor of _Sinosauropteryx_ and maniraptorans.
If tyrannosaurs were ALSO descendants of that common ancestor, than they
would be the descendants of feathered creatures.  Without additional data to
the contrary, the assumption would be that tyrannosaurs were themselves

                Thomas R. Holtz, Jr.
                Vertebrate Paleontologist
Department of Geology           Director, Earth, Life & Time Program
University of Maryland          College Park Scholars
                College Park, MD  20742
Phone:  301-405-4084    Email:  tholtz@geol.umd.edu
Fax (Geol):  301-314-9661       Fax (CPS-ELT): 301-405-0796