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ptero endothermy



Chris Bennett wrote:
> Some interpret the presence of
> that covering as evidence of bird-like and mammal-like endothermy;
however,
> that covering probably is better interpreted only as evidence that
> pterosaurs were insulated to some extent and probably used that
insulation
> to "improve" their thermoregulatory capabilities over what they would
be if
> uninsulated.

I agree with Chris.  I don't see any compelling evidence of endothermy
in pterosaurs.  Nothing about their flight style requires it.  A
crocodilian-like metabolism would probably suffice.  However, that
doesn't mean that they were exothermic either.

Jim

>>>

One of the reasons why pterosaurs were connected to dinosaurs for so
long was the morphology of the pelvis. In both the anterior process of
the ilium can be quite substantial. Greg Paul is better acquainted with
this than I, but one can see that the early dinosaurs (theropods, and
prosauropods) had rather small ilia while later forms had extended ilia.
Longer ilia means larger thigh muscles. Big thigh muscles are used
aerobically in dinosaurs -- burning more oxygen, which creates heat,
yada yada. Endothermy. (How bad did I botch that scenario?)

Pterosaurs had big ilia and big thighs before they had wings (and before
dinos had big ilia). Look  at Cosesaurus, Sharovipteryx and now
Longisquama. All big ilia and big thighs. If you want to draw
conclusions you might speculate from the length of the ilia alone that
whatever dinos were doing with their big thighs, pteros did first. But
was it endothermy?

Unfortunately, some are saying (as in the recent Sci Am) that even T rex
might not have been an endotherm.

So, let the arguments fly.

About the pelage, well, Sharovipteryx had scales and big thighs, so the
two don't necessarily go hand in hand. Sordes had hair. But was it
enough for insulation? Not sure how, when or why hair appeared sometime
during the Jurassic.

David Peters
St. Louis