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RE: Tyrannosaurs with leathery skin, etc.



> From: owner-dinosaur@usc.edu [mailto:owner-dinosaur@usc.edu]On Behalf Of
> Larry Dunn
>
> Dinosaur restorations depicting leathery-
> ("elephant-") skinned animals are often criticized
> based on fossil evidence that some dinosaurs had scaly
> skin.
>
> _Pelecanimimus_ at least apparently had smooth skin
> (and presumably feathers).

Importantly, the only patch of the integument clearly preserved was on the
dewlap/throat pouch/whatever.  This was naked.  Of course, throat pouches
are sometimes naked in animals with other sorts of integument (pelicans, for
instance).

> So what about
> _Tyrannosaurus rex_?  That ballyhooed skin imprint was
> only *associated* with the T. rex find, correct?

Correct.

> So, assuming it had feathers when newly-hatched as is
> currently being knocked about (a big assumption), and
> then shed its feathers as it grew, what would be left
> skinwise on an adult animal?  Animals don't develop
> scales as they age, do they?  Does this lead to
> elephant-skinned tyrannosaurs?

Animals CAN develop scales as they age: experimental mutant chickens show
that the same follicles that typically produce feathers can produce scales,
and vice versa.

> Further to this, if _T. rex_ chicks (or whatever the
> hell they are called) had feathers for insulation, how
> would "non-coelurosaur" theropod chicks be any
> different in terms of a need for feathers?

Not fully warm-blooded...?

Honestly, remember that the reason tyrannosaurids are now thought to be
descended from feathered animals is that they are phylogenetically bracketed
by known feathered critters.  Thus, it may not have been a *need* of
tyrannosaurid chicks, but of the ancestral coelurosaur chicks.
Tyrannosaurids inherited this condition from their ancestors.

It is also important to point out that we currently do not have a secure
"lower bounds" on the origin of feathers: it COULD be a coelurosaur
character, but it could also be an avetheropod character, or a tetanurine
character, or even a general theropod character (requiring adult
_Carnotaurus_ to have lost their feathers).  The coelurosaur position
represents the best "upper bound" position based on current evidence.

                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
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