A hypertragulid from the Sespe uppermost Eocene, California

Abstract

It becomes increasingly clear that the faunal stage represented at Locality 150 in the Sespe deposits north of the Simi Valley, California, marks an advance beyond the stage or stages recorded lower in the stratigraphic sequence of the Sespe as exposed in this region. Determination of age of this fauna as Eocene is maintained for the reasons stated in the first paper(1) announcing the discovery of Eocene mammals in California. Future survey of the fauna as a whole and recognition of relationships of the assemblage to comparable faunas found elsewhere may contribute toward elevating rather than toward depressing the fauna in the geologic time scale. It suffices for the present to state that the assemblage appears to be close to or within the Eocene-Oligocene transition period in the Tertiary history of vertebrate life for North America. In order to distinguish this stage from the upper Eocene fauna or faunas occurring lower in the Sespe section, the age designation uppermost Eocene is now applied to the assemblage.