Amphibians and squamates in the Eocene of Europe: what do they tell us?

The fauna of amphibians and squamates during the Eocene in western Europe resulted initially from the addition of an old, ante-Eocene fauna, and of a new fauna that arrived as a big wave of dispersals at the beginning of the Eocene (MP 7). These dispersals were likely favoured by the tropical climate. The fauna, as a whole, included taxa with Laurasian affinities, some of which indicate relationships with North America. However, some taxa showed South American affinities. The subsequent fauna (MP 8+9 and MP 10) developed from that of MP 7 and was not affected by peculiar events. The fauna of the MP 11-MP 15 interval (middle Eocene) is poorly known. The last interval (MP 16-MP 19 +20, latest middle and late Eocene) is characterised by a rich and diverse fauna, despite temperatures lower than that of the early Eocene. This fauna perhaps partly originated during the preceding interval. Richness and diversity resulted from dispersals and local radiations; autochthonous forms were apparently rather frequent. This fauna still included taxa with South and North American affinities. At the end of the Eocene, there occurred a prominent extinction event, the 'Grande Coupure'. Most taxa were eliminated, at least in western Europe; they survived elsewhere, permitting subsequent repopulation. The Grande Coupure was a pivotal event. Before it, the faunas were indicative of warm climates and included American components; after the Grande Coupure, the faunas that progressively repopulated Europe were indicative of less warm climates and no longer included American forms. [ABSTRACT FROM AUTHOR]