RE: Bird reduce their "heating bills" in cold climates

[Tim Williams <tijawi@yahoo.com>]

Jura <pristichampsus@yahoo.com> wrote:


> I do nothing of the sort. That some maniraptorans (notably
> "Dave") preserve scales on the tarsometatarsal region, just
> shows that by that time, scales had re-evolved in that
> lineage. It's not like you were seeing a scaly face, and
> tail too, or scales intermingled with feathers on the body.


Rather than invoking wholesale loss and "re-evolution" of scaly integument, in 
this case wouldn't it be more reasonable to propose that the absence of scales 
from certain parts of the body (e.g., the face) was a preservational artifact?


If "Dave" (NGMC 91) preserves scales on the tarsometatarsus, but nowhere else, 
this is likely due to taphonomy.  Overall, for any given Yixian specimen, the 
preservation (or not) of the integument is an erratic process.  In fact, as 
stated previously, most Yixian specimens do not preserve scales at all - even 
those taxa that might be expected to have a fully scaly body covering.  For 
example, the ornithischian _Jeholosaurus_ has no integument preserved at all.  
Preservation of the scaly integument is not "all-or-nothing" .  The same 
applies to the filamentous integument (feathers and their homologs) of Yixian 
birds and related maniraptorans.  



Cheers

Tim