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Steel, Lorna wrote:
> 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.

The amount of energy used in flapping would be expected to be
proportional to the wingloading, and inversely proportional to the
aspect ratio.  An animal with high wing loading and high aspect ratio
wouldn't necessarily spend all that much time flapping.  For example
both types of Q could make do quite handily with occasional bursts of 1
to about 15 or 20 wingbeats followed by relatively long periods of
quiescence.  That, taken together with the long dead air column in their
necks makes me wonder about their capability for aerobic flight (they
didn't need it, and weren't well equiped for it).

> My point would be, look at the bone histology. Not many people have, but you
> 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 birds
> 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.

It likely will.  So far (if I remember correctly) not all evidence
related to pterosaur bone histology leads toward an assumption of
endothermy (I'd defer to Chris on this).