Re: soggy "down" maladaptive?

[Dino Guy and Computer Gal <gbabcock@best.com>]

> In a message dated 4/27/01 1:10:50 PM Eastern Daylight Time, ornstn@home.com
> writes:
>
> > For one thing, I do not see its relevance.  Whatever else the structures on
> >  Sinosauropteryx, the new critter etc are, they are certainly not "down" in
> >  the neornithine sense - ie a plumulaceous puff arising from a common
> >  base.

Regarding _Sinosauropteryx_ dinofuzz, protofeathers, feathers, what have you:
Philip Currie, having seen larger hollow fiber cross-sections in the vicinity of
_Sinosauropteryx_ specimens, in addition to the more well known finer fibers
which were actually arrayed in close proximity to the skeletons, had 
hypothesized
that these coarser hollow structures might represent the remnants of the short
central hollow stem to which the finer filaments had been attached (similar to a
down-like configuration).  Currie had projected microphotographs of these 
hollow,
sectioned fibers at public presentations in the year following the description 
of
_Sinosauropteryx_.  The cross-sections were also featured in the original 
Chinese
language description of _Sinosauropteryx_, which refers to them also, I believe.
This was the initial _Sinosauropteryx_ paper which asserted that the animal in
question was a bird (because of the feathers).  Currie briefly explained his
thoughts regarding the morphology of these features in answer to my question via
the "Dinosaur Dish" forum at the Dinosaur Interplanetary Gazette web site.  Of
course, this characterization is speculative, and the hypothesis has yet to be
officially published or corroborated by new evidence.  Who knows?

Currie had also initially reported what looked to him to be a central rachis 
with
associated filaments in some areas of the _Sinosauropteryx_ integument.  As far
as I know, other paleontologists have not backed him up on this, either.  It's
apparently hard to lay out the precise morphology of these structures.

On the other hand -- and I've written this before -- the _Nature_ paper
describing _Sinosauropteryx_ describes the filaments as being relatively coarse,
hollow structures.  They are described as being coarser than the fur fibers of
extant mammals of comparable size.  So for _Sinosauropteryx_, at least, it would
seem that this type of pelage may have been better suited for insulation than
small mammal fur is today, and I don't see our small mammals dispensing with
their fur when the rains begin (excluding naked mole rats, which have no respect
for such sweeping generalizations, and which brazenly parade through their
secluded tunnels as if members of diminutive nudist colonies).  I'm sure _Sino_
and friends were just fine (even if their filaments were coarse).

-- Ralph W. Miller III   ralph.miller@alumni.usc.edu

Corrections and rebukes gratefully accepted.