Re: competition between Pterosaurs and birds (fwd)

[nhi158@aberdeen.ac.uk]

Forwarded message:
>From nhi158 Wed Jan  4 10:41:00 1995
Subject: Re: competition between Pterosaurs and birds
To: ornstn@hookup.net
Date: Wed, 4 Jan 1995 10:41:00 +0000 (GMT)
In-Reply-To: <199501031648.LAA07547@noc.tor.hookup.net> from "Ronald Orenstein" 
at Jan 3, 95 05:51:58 pm
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I have been following the discussion of the potential competition of birds and
Pterosaurs with some interest since I currently have a paper in press concering
competition between insectivorous birds and bats (Rydell and Speakman Biol. J.
Linn Soc. vol 53 pages unknown yet). There are some facts which seem to have
been overlooked in the current discussion which people may be interested in. 
First most of the small insectivorous Pterosaurs (the Rhamphorhynchoidea - eg
Pterodactylus Sordes and Batrachognathus) are all late Triassic or Jurassic
lineages which became extinct before the Cretaceous. The earliest birds
originated in the late Jurrassic but were probably not flying until the
cretaceaous. It is currently unclear wether any Mesozoic birds were aerial
insectivores (Olson 1985). Current small insectivorous birds which would be
potential competitors for the Pterosaurs all evolved very much later. The swifts
(Apodidae) appear in the late Eocene although an extinc group the
Aegialornihidae evolved slightly earlier in the early Eocene (Peters 1985). The
hirundines which are passerines appear even later in the Miocene and Pliocene. 

As it stands the fossil record has a gap between the last small insectivorous
Pterosaur and the first small insectivorous bird. For bats the fossil record
suggests the first bats originated around the Paleocene /Eocene (Stucky and
McKenna, 1993 In Benton The fossil record). The first bats however are fully
formed aerial insectivores almost identical to current forms so an earlier
origin is likely. Even so it seems improbable that the bats originated in the
late Jurrassic when the small insectivores were dying out. 

These timings strongly suggest that small insectivorous Pterosaurs and small
insectivorous birds and bats were separated by around 50-70 million years. It
thus seems very unlikley that either birds or bats acted as competitors with the
insectivorous Pterosaurs. Thus despite all the arguments about niches being
filled etc it does seem that the aerial insectivore niche was either unfilled or
not existent during most of the Cretaceous period. 

Cheers

John Speakman

J.R. Speakman@aberdeen.ac.uk
Tel +44 224 272879
Fax +44 224 272396

Department of zoology,
University of Aberdeen,
Aberdeen,
AB9 2TN