Re: Feathered Theropods -Reprise

[Scott A Hartman <ottscay@uwyo.edu>]

In modern, tropical climates, 400 kg is around the limit after which size
alone suffices as insulation.  Please, don't anyone write back that humans
are naked.  I'm well aware of my personal insulatory pellage (which, I
dare say, is a good deal thicker than many of yours).  Howver, no humans
are without insulation.  In modern communities, we use clothes and housing
to protect ourselves.  In hunter-gatherer societies, primitive housing,
fire, and behavior serve as insulation.  Pigs use fat as insulation.
However, I doubt that fat serves as an advantageous alternative in
non-domesticated animals, because it slow down locomotion, while
simulatneously increasing your appeal to predators.  Take a gander at
Walkers Mammals of the World, and you'll see, no African mammal below 400
kg is without insulation.  That's because insulation insulates you from
hot environments as well as cold ones.  Surface conditions (i.e skin) can
get as much as twice as hot as the ambient temperature.  These conditions
will kill animals that don't either retreat to shade or have insulation
(remember, size is a viable form of insulation, but not until WAY beyond
the size of velociraptor or oviraptor).

So if you want to draw velociraptors with scaly hides, don't have them
doing anything an endotherm would do (which is, I'l point out, a
perfectly acceptible position to take, just be consistent).  Also, the
disclaimer that accompanies pebbly skinned dromeosaurs should say: This
illustration flies in the face of the scientific doctrine of parsimony, as
well as contridicts recent work in archosaur systematics.  Then, I'll
attach the disclaimer to feathered theropod illustrations which will
say:ALthough close relatives of Velociraptor (i.e protarchaeopteryx) have
full blown feathers, there is no direct evidence that veolociraptors had
feathers, or even protofeathers.

Finally, As outlined by Witmer (see last years JVP supplement), assesing
the possesion of soft tissue structures based on ohylogenetic bracketing
is NOT speculation, but induction.  It presents its own hypothesis, which
can be tested and falsified as new specimens further resolve the fossil
record.

Scott Hartman

On Sun, 27 Sep 1998, TRUETT GARNER wrote:

> Firstly , 
> Thanks to Jeff for a very succinct explanation of his viewpoint,( which I
> highly respect ) and thanks to Brian for bringing the issue more into focus
> . Didn't mean to start a firestorm . My basic problem with feathered
> Oviraptorids or Dromaeosaurids has to do with size in both animals . I
> understand that Oviraptorids and Dromaeosaurids are considered ' small '
> theropods , but are they not both larger than
> the feathered theropods from China ? In other words , what is the upper
> size limit in which insulation (discounting display purposes)
> becomes unnecessary in an endothermic dinosaur living in a fairly equable
> environment ?
>  Regards , Truett Garner
>