Re: Feathers

[HPB1956@aol.com]

Re: feathers

Paul Sparks wrote

> In the march issue of Scientific American there is an article by Richard
> Prum and Alan Brush entitled "Which came First the Feather or the Bird'.

. . .

> The feather development was pretty good I thought
> The attachment of that description to the fossil record was pretty hasty
> and devoid of detail especially wrt the #3 feather which is pretty important


I haven't seen the article because here in Germany the March issue of
SciAm isn't available yet.

But try http://www.mcorriss.com/Prum_&_Brush_2002.pdf for
downloading another article by Alan Brush and Richard Prum.
The citation is 

THE EVOLUTIONARY ORIGIN AND DIVERSIFICATION OF FEATHERS.
Richard O. Prum & Alan H. Brush.
Quarterly Review of Biology 77 (3):261-295 (2002)

The article in SciAm will correspond to this article in Quarterly Review
of Biology from September 2002.

On page 279 of the PDF-file there's a cladogram of theropod dinosaurs
(Sereno 1999) showing possible points of origin for their postulated Stages
I - V of feather development.

According to this cladogram Stage III (development of rachis and barbules) may
have taken place either in
- Paraves = (Dromaeosauridae + Troodontidae) + Ornithurae
- Maniraptora = Oviraptorosauria + Paraves
- Maniraptoriformes = anything else in Coelurosauria except some basal forms

IMHO Prum and Brush are very cautious in assigning developmental stages onto
theropod taxa. E. g. they put the origin of Stage I (follicle) inside basal
Coelurosauria. This is according to the known fossil evidence. AFAIK no non-
coelurosaurian theropod with any sign of "feathery" integument has been
found (Am I correct?). But this is only negative evidence just saying
"We don't know for sure".

And there's the "spiky" Psittacosaurus sp. with his strange integument (kind
of a mesozoic porcupine?) which shows that dinosaurs as a whole where able to
develop some kind of integument, may it be "hairy", feathery, "spiky" or 
whatsoever. So I think that it's very likely that the Stage I (follicle) 
developed outside Coelurosauria, perhaps somewhere in basal theropods
or even basal dinosaurs.


Cheers


Heinz Peter Bredow