Re: Sinosauropteryx tail colors

[Tim Williams <tijawi@yahoo.com>]

Saint Abyssal <saint_abyssal@yahoo.com> wrote:

> The article Dr. Holtz linked to
> reports one of the paleontologists as saying that he
> believes that feathers were used for color-utilizing sexual
> displays before being exapted for insulatory purposes and
> later flight. Am I the only one who thinks the "display to
> insulation" scenario sounds backwards? Feathers are by
> nature useful for insulation, but in the absence of showy
> fans or crests as exemplified by compsognathids like
> *Sinosauropteryx*, what display advantage would they have
> over plain scales? "Naked" scaley reptiles can be perfectly
> bright and colorful on their own; no novel structures are
> needed. 


That's a really good question.  Nevertheless, if we look at the elaborate bony 
structures that adorn the skulls of many non-avian theropods, it would seem 
that scales alone weren't cutting it.  The crests of _"Syntarsus" 
kayentakatae_, _Ceratosaurus_, _Monolophosaurus_, _Cryolophosaurus_, 
_Baryonyx_, _Allosaurus_, _Proceratosaurus_, _Guanlong_, etc etc all seem to 
have no apparent function aside from display.  (The same might apply to the 
integumental structures of _Tianlong_ and _Psittacosaurus_, and perhaps the 
dorsal sails of tall-spined theropods, sauropods, and ornithopods.)  


Display was obviously important to theropods, hence the investment in cranial 
crests in many non-avian theropod taxa.  It may be that the first feathers took 
over from bony cranial crests - although they weren't mutually exclusive (e.g., 
_Guanlong_, some oviraptorosaurs).  But if display can drive the evolution of 
something as weird and "showy" as the cranial crests of _Dilophosaurus_ or 
_Guanlong_, then this same selective pressure could be behind the appearance of 
an evolutionary novelty such as feathers.


Cheers

Tim