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Re: Large last gasp of pterosaurs
----- Original Message -----
From: "Graydon" <firstname.lastname@example.org>
Sent: Thursday, January 22, 2004 3:36 PM
Subject: Re: Large last gasp of pterosaurs
> On Thu, Jan 22, 2004 at 11:40:39AM -0600, Tim Williams scripsit:
> > John Bois wrote:
> > >Except that this then opens up the far more interesting question of
> > >what complex ecological factors actually killed most pterosaurs.
> > Competition with birds?
> There are, to my mind, four serious problems with invoking 'competition
> with birds'.
> 1) we don't have any evidence for it, no strata where the pterosaurs
> give way to shore birds, frex. The few mixed communities we have
> evidence for have way more pterosaurs than birds. (7 Archeopteryx
> versus how many pterosaurs?)
> 2) pterosaurs had a very considerable head start for feeding
> specializations and a fundamentally different mode of flying; it's not
> clear that there would be direct competition for food, or that early
> birds could reasonably expect to compete with pterosaurs for food at
> all. Food that different modes of flying made available to birds that
> wasn't available to pterosaurs wouldn't have been part of the
> pterosaurian diet in the first place.
> 3) both groups of fossils are generally very rare, sparsely represented,
> however you want to put it. I don't know of any case where someone has
> been able to demonstrate that there is a statistically significant
> decline in the pterosaurian population.
> 4) nest predation scenarios seem to assume altricial-model mostly
> helpless nestlings. I don't think this is a supported assumption -- do
> we have any pterosaur nestling fossils? -- and a baby Pteranodon or a
> baby Quetz. half the size of its parents would be quite well able to eat
> an eagle if the eagle was crazy enough to try to predate it.
I have argued (see Bennett, S. C. 1993. The ontogeny of Pteranodon and
other pterosaurs. Paleobiology, 19:92-106) that large pterodactyloids liek
Pteranodon were altricial and like many extant birds stayed "in the nest"
and relied on parental feeding until they grew to virtually adult size,
whereupon they would leave the nest and begin flying and feeding
indepentdently. I have also argued that this was not the case in smaller
pterosaurs such as Rhamphorhynchus and Pterodactylus.
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