North American Eocene Sea Cows (Mammalia: Sirenia)

Abstract

The record of Eocene sea cows in North America is reviewed in detail, and that of the world is summarized. The North American record includes some 20 localities, mostly yielding fragments identifiable only as sirenian. Of these, the most extensive materials are a partial skeleton from the Cook Mountain Formation of Texas, numerous isolated elements from the Avon Park Formation of Florida, and a partial skeleton and other specimens from the Castle Hayne Formation of North Carolina. The materials from North Carolina and Florida are middle Eocene in age and are referred to <i>Protosiren</i> species. These specimens provide further confirmation of the fact that Eocene sirenians had a 3.1.5.3 dental formula and were the latest eutherians known to exhibit five premolars. The implications of this for the higher classification of mammals are discussed. The distribution of sirenians suggests a homogeneous middle Eocene Tethyan fauna and also seems to be a more useful guide to the former distribution of seagrasses than are the distributions of Foraminifera. Eocene sirenians have potential value in intercontinental biostratigraphic correlation.