Re: Follow-up: the truth about killer dinosaurs

[Michael Mortimer <mickey_mortimer111@msn.com>]

T. Michael Keesey wrote-

> > Though none of the tyrannosaurid skin impressions has been specified to 
> a
> > certain body area, are we to believe they were all pedal?
>
> If they can't be assigned to a specific body area, are we even sure
> they're tyrannosaurid? (I admit I don't know the details very well.)

One was found by the ilium and gastralia, but the skeleton was 
disarticulated (Tanke, DML 1996).  The Gorgosaurus impression which lacked 
scales (Currie, 2001) and MOR impressions noted by Tanke haven't had their 
position described.

> > I can't picture replacing feathers with scales, but what if the 
> juveniles
> > had scales with feathers in between (like opossum tails have scales and
> > fur), then shed the feathers perminantly on the way to adulthood.  Of
> > course, if I'm going to posit that, I wonder if impressions of 
> interspersed
> > feathers would be preserved at all in Judith River sediments (or 
> Morrison or
> > La Colonia for that matter).
>
> Moreover, _Dilong_ doesn't show this, so it would have to be a derived
> trait of tyrannosaurids. Simpler hypothesis: sparse feathers in adult
> tyrannosaurids, along with areas of scutellae (including at least the
> feet).

Dilong doesn't not show it though.  Remember, the soft tissue over the body 
often decayed in Yixian animals.  That's why we get halos of integument for 
the most part in coelurosaurs.  In Dilong, we have tail feathers dorsal and 
ventral to the vertebrae and chevrons, with absolutely nothing preserved 
where any skin or scales would be.

Mickey Mortimer