Title Information

Münchner Geowissenschaftliche Abhandlungen
Reihe A: Geologie und Paläontologie

Volume 16

LEGENDRE, Serge: Les communautes de mammiferes du Paléogene 1989. [in French] – 110 pp., 49 figures, 6 tables, appendix. 29.7 x 21.0 cm. Paperback ISBN 978-3-923871-35-3 Euro 30.00 series: MGA, Reihe A: Geologie und Paläontologie order now

Abstract

A method of analysis of mammalian communities has been developed: the cenogram method. Cenogram analysis involved plotting the body weight of each component species in a fauna on a semilog diagram in rank order.

Cenograms has been drawn for 42 recent mammalian faunas mainly from Africa, South America, and North America, but also from Europe, Asia, and Australia. The study shows that some structures in the body-weight distribution of species within a community are linked to main environmental features (such as the vegetational cover density, humidity, and temperature).

The use of this method in paleontology requires an estimation of the body weight of fossil species. This estimation is done, using the very strong correlation between the tooth area and the body-weight in recent mammals. It is possible to evaluate the body weight from the first lower molar, using for calculation the parameters of the allometry between these two factors. The allometric parameters were calculated for various groups of mammals.

Applied to the analysis of mammalian communities from the Paleogene of Western Europe, this method shows changes occuring in the environment of faunas: at Oligocene times, a semi-arid and more open environment succeeds to the late Eocene tropical rain forest environment. The change in community structure, which is related to drastic eco-climatic changes, is contemporaneous, in France, with an important faunal change, known as the "Grande Coupure". This continental event seems to be concordant with a paleoceanographical event, the Terminal Eocene Event.

The fact that recent mammalian communities are structured, that these structures persist through time, and that structure changes occurred with climatic changes, led to discuss a hierarchical model of evolutionary phenomena and also to propose that evolution exists at the community level, with mode and tempo distinct from those occurring at the species level.