Re: HESPERORNITHID FEATHERS etc

["Tim Williams" <twilliams_alpha@hotmail.com>]

Darren Naish wrote:

> I think the argument is that their integument was down-like, if you
> will), Tim wrote..
>
> > Feather impressions found associated with one hesperornithid specimen
> > are very hair-like...
>
> Apparently the thing about hesperornithiforms having plumalaceous
> feathers is not right. Per Christiansen has discussed this in an MS
> which I think is in press (pers. comm.).

Apart from reading about hesperornithid feathers in the original 
description, I saw it repeated in Chatterjee's _The Rise of Birds_.

Which aspect is incorrect - that the feathers are plumulaceous, or that the 
traces/impressions are even feathers at all?  (Of course, if it's in the 
process of publication, I'll shut my trap and wait for the paper.  ;-)  )


> On _Archaeopteryx_: I forget where I read it, but don't the bases of
> _Archaeopteryx_ feathers have plumalaceous tufts? These are at least
> suggestive of an insulative function.

I can't answer that question, but I think it's pertinent to mention that (as 
I'm sure Darren is aware) that part of Feduccia's opposition to birds 
evolving from theropods stems from his belief that feathers evolved FIRST 
for flight and LATER for insulation.  In other words, down feathers 
represent a secondary simplification of the more complicated flight 
feathers.  Feduccia sites the presence of a central rachis (shaft) and barbs 
in the down feathers (plumules) and body contour feathers.  He claims that 
this arrangement in non-flight feathers could only arise if they were 
derived from flight feathers, where the shaft and vane evolved for a purely 
aerodynamic purpose.

I don't buy it.  The "pre-feathers" of _Sinornithosaurus_ and _Microraptor_, 
in the form of simple tufts or with many filaments branching from a central 
shaft, would make superb heat-trapping structures.  Each filament in a tuft 
would serve the same purpose as a single mammalian hair.  Apart from making 
good sense, Richard Prum's developmental model for the origin of feathers is 
highly corroborated by fossil data.


Tim

------------------------------------------------------------

Timothy J. Williams

USDA/ARS Researcher
Agronomy Hall
Iowa State University
Ames IA 50014

Phone: 515 294 9233
Fax:   515 294 3163

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