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Re: Pterosaur endothermy

----- Original Message -----
From: "Steel, Lorna" <Lorna.Steel@iow.gov.uk>
To: <dinosaur@usc.edu>
Sent: Thursday, January 29, 2004 9:00 AM

> Re pterosaur endothermy:
> We are starting to think that these animals had various flight styles,
> ranging from gliding (without using much energy) to lots of flapping
> (probably used lots of energy). OK, that doesn't solve the argument.
> My point would be, look at the bone histology. Not many people have, but
> always see evidence of rapid growth (usually uninterrupted) in pterosaurs.
> Birds grow rapidly, and ectothermic reptiles don't (unless you feed them
> lots and keep them warm, but even then, they don't grow as quickly as
> and mammals). I could go on, but I am sure you don't want me to! This
> argument is a tricky one, but I think that further progress in
> palaeohistology will provide more evidence one way or the other.

Two points:  1. I agree that paleohistology will provide more evidence, and
that most of the recent studies have shown rapid growth.  However, some have
identified lines of arrested growth.  The problem is that almost all of our
data come from pterodactyloids.  Some years ago I reviewed the manuscript
for a paper by Padian, de Ricqles, Horner, and Francillon-Vieillot entitled
"Paleohistology of the bones of pterosaurs (Reptilia:  Archosauria):
anatomy, ontogeny, and biomechanical implications"--sorry I do not have the
reference.  They, too, suggested that the evidence indicated rapid growth,
but careful examination of their data table revealed [if I remember
correctly] that all but one specimen was a pterodactyloid and the single
non-pterodactyloid specimen was Jurassic and represented by two small
fragments.  We cannot generalize and state that all pterosaurs had rapid
growth if we have almost no data about Jurassic taxa and none about Triassic
taxa.  Note also that I argued that the year-class data for Rhamphorhynchus
suggested growth rates no greater than extant Alligator.

2.  Rapid skeletal growth does not necessarily indicate endothermy.


S. Christopher Bennett, Ph.D.
Assistant Professor of Basic Sciences
College of Chiropractic
University of Bridgeport
Bridgeport, CT  06601

"Savor the sun--but when the clouds come make animals"  (Hexum)