Re: Follow-up: the truth about killer dinosaurs

[Tim Williams <twilliams_alpha@hotmail.com>]

T. Michael Keesey wrote:

> I get tired of hearing this excuse for artists to maintain the
> "classical" view of tyrannosaurid integument.

I guess it may depend upon the "tyrannosaurid" (or "tyrannosauroid") in 
question.  Tyrannosaurid skin impressions from Canada show a more-or-less 
"classical" scaly integument, so this may be typical for the big-ass Late 
Cretaceous tyrannosaurids.  But _Dilong_, a smaller and more primitive 
relative, shows those new-fangled feathers (or precursors of feathers).  
Feathery-ness in theropods may be a consequence of many factors: size, 
climate, seasonality, age...

On that last one, juvenile _T. rex_ might have been endowed with natal down, 
which was shed from most of the body as the creature got older and bigger, 
as Mike suggests...

> And is the analogy completely valid? Tyrannosaurids, like all
> archosaurs, hatched from eggs, and so began life well within the size
> range of animals which insulation can benefit. Perhaps they became
> less fuzzy as they grew (indeed, elephants are born somewhat hairy,
> then lose the meager fuzz), but is there any reason to suspect it
> fully disappeared?

Perhaps adult _T. rex_ had fuzzy eyebrows, sprouting from those peculiar 
lacrimal crests.  :-)  We know that many non-coelurosaurian theropods show 
elaborate cranial crests made of bone - so why not decorative crests made of 
feathers in the coelurosaur groups?  At least one _Microraptor_ specimen 
shows a mane-like crest - why not _T. rex_?

Cheers

Tim