[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index][Subject Index][Author Index]
Re: Winged migration
----- Original Message -----
From: "John Bois" <firstname.lastname@example.org>
Sent: Wednesday, July 23, 2003 5:47 PM
Subject: Re: Winged migration
> On Wed, 23 Jul 2003 GSP1954@aol.com wrote:
> > What I am wondering is where they got the figure of 80 million years
> > that birds have ruled the skies. Birds were present almost twice as
> > abundant by the Early Cretaceous, but pterosaurs were still around 65
> > years ago.
> Pterosaurs were reduced to a very few niches by 65mya. Diversity in all
> but the largest size ranges was being diminished well before that
> time. Unwin says this, I believe.
Well if Dave says it, then it must be true, right? I might as well delete
my unfinished manuscripts, return my borrowed specimens, and resign my
academic position because my interest in evidence is unnecessary when we can
rely instead on authority. If Dave is the pterosaur authority, then who is
the comparable dinosaur authority? Holtz? Bakker? Sereno?
The Upper Cretaceous pterosaur record is not very good except for a few
localities, and in my opinion it is not good
enough to support the assertion that pterosaur diversity was reduced or
limited to the largest sizes. A little bit of negative evidence is not very
convincing, especially when one considers how spotty the entire pterosaur
record is. Our knowledge of Lower Cretaceous pterosaur diversity is based
in large part on the nearshore Santana and Greensand deposits, and there is
no comparable Upper Cretaceous nearshore deposit. The non-marine
anurognathids are represented by only about six specimens that are widely
scattered geographically and temporally. It is possible that there was a
diverse nearshore pterosaur fauna in the Upper Cretaceous right up until the
end-Cretaceous extinction, and also possible that the anurognathids hung on
until the extinction.
S. Christopher Bennett, Ph.D.
Assistant Professor of Basic Sciences
College of Chiropractic
University of Bridgeport
Bridgeport, CT 06601