Re: Jurassic Park

[<TWILLIAMS@canr1.cag.uconn.edu>]

> 
> It's *real* simple: _Sinosauropteryx_, a compsognathid, had hair-like
> "proto-feathers". Birds have feathers. In pretty much every phylogeny
> published recently, dromaeosaurids share more recent ancestry with birds
> than with compsognathids.

_Sinosauropteryx_ may have had feathers, but there's no evidence that 
_Compsognathus_ (the only other known compsognathid) did.  The 
type specimen of _Compsognathus_ from Bavaria is quite naked, yet 
pterosaurs and _Archaeopteryx_ from the same limestones show at 
least some trace of body covering - fur for pterosaurs, feathers for 
_Archaeopteryx_.

Tim




> Hence:
> 
> |--_Sinosauropteryx_ ("proto-feathers")
> +--+--_Velociraptor_ (skin impressions unknown)
>    +--Aves (feathers)



> It is parsimonious to assume that "proto-feathers" and feathers are
> homologous. Therefore, _Velociraptor_ either had integument or secondarily
> lost it. I can think of no reason why a small, non-burrowing, non-aquatic,
> non-wallowing animal like _Velociraptor_ would lose integument. 
> 
> Of course it's not proven, since we don't have dromaeosaurid skin
> impressions, but that's why Scott said "*almost* certainly".
> 
> It is for similar reasons that we assume animals like _Ichthyornis_ were
> feathered.
> 
> --T. Mike Keesey                                   <tkeese1@gl.umbc.edu>
> DINOSAUR WEB PAGES -- http://www.gl.umbc.edu/~tkeese1/dinosaur/index.htm
> 
> 
>