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Re: Birds vs. the pterosaurs
Birds vs. the pterosaurs
There have been a few papers on this subject. See for example:
Buffetaut, E., Clarke, J. B. and Le Loeuff, J. 1996. A terminal Cretaceous
pterosaur from the Corbieres (southern France) and the problem of pterosaur
extinction. Bull. Soc. geol. France. 167, 753-759.
Unwin, D. M. 1987. Pterosaur extinction: nature and causes. Memoires Sociéte
Geologique de France, 150: 105-111.
Unwin, D. M. 1988. Extinction and survival in birds. In: Larwood, G.P. (ed.),
Extinction and Survival in the Fossil Record. Systematics Association Special
Volume 34, 295-318, Clarendon Press, Oxford.
and the subject is also treated by Wellnhofer in the Encyclopedia,
Wellnhofer, P. 1991. The Illustrated Encyclopedia of Pterosaurs. Salamander
Books, Ltd., London, 192 pp.
Combining our current understanding of pterosaur phylogeny (see for example
Unwin, D. M., Lü, J. & Bakhurina, N. N. 2000. On the systematic and
stratigraphic significance of pterosaurs from the Lower Cretaceous Yixian
Formation (Jehol Group) of Liaoning, China. Mitteilungen Museum für Naturkunde
Berlin, Geowissenschaftlichen Reihe, 3, 181-206), with a current data base for
the Cretaceous pterosaur fossil record suggests that pterosaur diversity
declined in the Late Cretaceous, and, by the Maastrichtian, only a few species
(practically all of them azhdarchids, were left). Pterosaur bones are quite
distinctive, and so far none have turned up in post Mesozoic sediments, so it
looks as if pterosaurs did not make it through the K-T boundary. It is possible
that birds had some impact on pterosaur evolution. It might be, for example,
that in the Cretaceous, birds opportunistically filled 'niches' vacated by
pterosaurs through normal extinction processes and thus slowly displaced pter!
osaurs in an indirect way. However, there is very little direct evidence to
support this, and in any case I suspect that ecologically specking, while
pterosaurs may have overlapped with birds to some extent, pterosaur 'niches'
were probably different from those of birds and the two groups were capable of
coexistence, perhaps with a little friction at the edges. Climatic conditions
(strong or gusty winds) have often been cited as potentially lethal for
pterosaurs, but even giant forms were around for millions of years. Since these
and other pterosaurs were, undoubtedly, well adapted to the environments in
which they lived it is likely that only really extreme conditions that spread
world-wide are likely to have finished off entire species.
The bottom line is that even with an incredibly dense fossil record (e.g. as
for microfossils), remarkably good temporal and stratigraphic control and huge
amounts of data on environmental conditions, and their geographic and historic
variation, it is well nigh impossible to determine how or why groups such as
pterosaurs or dinosaurs became extinct. Still, its fun (and stimulating) to
speculate, and maybe someone will tackle pterosaur extinction at the pterosaur
meeting to be held in Toulouse in early September.
David M Unwin
Curator for Fossil Reptiles and Birds
Institut fur Palaontologie
MUSEUM FUR NATURKUNDE
Zentralinstitut der Humboldt-Universitat zu Berlin
0049 30 2093 8577 (office)
0049 30 2093 8862 (department secretary)
0049 30 2093 8868 (fax)
web site: http://www.museum.hu-berlin.de/pal/vertp/unwinvp.html