Palaeocene

Palaeocene The first epoch of the Cenozoic era, the Palaeocene (also spelt Paleocene) was distinguished by Wilhelm Schimper in 1874. It spans the time from the end of the Cretaceous (65 Ma) to the beginning of the Eocene (54 Ma). Like the other Cenozoic epochs, it was based on a type section in France. There are two stages, a basal Danian and an upper Thanetian/Selandian (two different facies-types).

At the inception of the Cenozoic, Laurasia, like its southern counterpart Gondwanaland, began to split apart. Ocean-floor spreading began to expand the North Atlantic northwards, with a new gulf extending from near Gibraltar to the vicinity of present-day Newfoundland. Canada and Greenland were meanwhile still attached to Europe. Africa and Arabia were joined but Madagascar had separated. India had yet to make contact with the southern margin of Asia. A warm climate prevailed everywhere, with more precipitation over the land than there had been in Cretaceous times. Antarctica had not yet reached its fully polar position and was only just beginning to exert a cooling influence upon the southern hemisphere.

The Palaeocene biota, both marine and terrestrial, contrasted sharply with that of the Cretaceous. In the seas, only the gastropods and bivalvia remained common among the bottom-dwelling mollusca; some nautiloids persisted but the ammonoids were not extinct. On land, new orders of plants, including the grasses and other modern types, flourished, but the deciduous forests were of low diversity. The spread of vegetation over an increasing part of the land surface now took place, assisted by the amelioration of the climate as Pangaea fragmented and new seas came into being. In their turn, the new forests and grasslands constituted habitats, and in the absence of the large reptiles that had been so active in the Mesozoic era, the mammals became the dominant tetrapods, spreading rapidly far and wide and evolving many large species. The contrast between the communities of very small Cretaceous mammals and the new Palaeocene faunas of large—even gigantic—mammals is very striking. South American mammal faunas included prolific numbers of marsupials. Elsewhere the ‘archaic’ orders of mammals reached prominence, and were not to disappear until Miocene times.

D. L. Dineley

Bibliography

Savage, R. J. G. and and Long, M. R. (1986) Mammal evolution, an illustrated guide. British Museum (Natural History), London.
Taylor, J. (1978) Cenozoic. In McKerrow, W. S. (ed.) The ecology of fossils, pp. 328–30. Duckworth, London.