RE: Dino/Birds? was Mesozoic snow? and fund for Antonio

[Tim Williams <twilliams_alpha@hotmail.com>]

Jeff Hecht wrote:

> Cladistically, there is a presumption that some sort of protofeather or 
> dinofuzz evolved fairly far down the theropod family tree, so everything 
> that is (say) above Sinosauropteryx had some kind of feather-ish body 
> covering. But we don't know when that development occurred. The lack of 
> evidence of feathers is not evidence of the absence of feathers.

For sure.  For example, the feather-ish body covering may be primitive for 
the entire Dinosauria - which would put those spiny _Psittacosaurus_ 
integumentary structures into perspective.  This body covering may go down 
even further in phylogeny (e.g., beyond the lagosuchians) or be limited to 
theropods or a subset of theropods.  In my previous example I was relying on 
the principal of phylogenetic bracketing in limiting the presence of 
feathers (or protofeathers) to everything above compsognathids or 
tyrannosauroids (depending upon which clade is more basal).  But there is no 
reason why coelophysids or allosauroids or even herrerasaurids might not 
have been endowed with this kind of body covering too.  However, at the 
moment the phylogenetic bracket for this character is hovering around the 
Coelurosauria, so I was playing it safe.

David Marjanovic wrote:

> So far very little has been published from that formation in general (at 
> least compared to the Yixian Fm)... or is that just my vertebratocentric 
> tunnel vision?

It may be partly due to your vertebratocentric tunnel vision (you must get 
that looked at, David).  I think there have been papers on the invertebrate 
fossils (e.g., crustaceans) of the Dabeigou formation.  But I have no idea 
how many studies have been publsihed.

Cheers

Tim