ABSTRACT

This chapter discusses a series of stratigraphically superposed middle Eocene mammal assemblages from coastal San Diego County. The Swami's Point local fauna (Delmar Formation) is the first fossil vertebrate assemblage of demonstrably Bridgerian age from southern California. The assemblage from the basal Scripps Formation (Black's Beach local fauna) is either of late Bridgerian or early Uintan age. Uintan biochronology is problematical, due to the lack of a rigorous biostratigraphic framework and other unsolved problems in the Uinta Basin. However, the early Uintan/late Uintan boundary can be characterized in southern California by the extinction of the common early Uintan genera Crypholestes, an unnnamed dormaaliid insectivore, Omomys, Washakius, Metarhinus?, and Merycobunodon, and by the evolution and/or immigration of the common late Uintan genera Sespedectes, Proterixoides, Dyseolemur, Rapamys, Griphomys, and Simimys.

The early Uintan Poway fauna is redefined as the entire set of vertebrate taxa occurring in the Friars Formation. The Mesa Drive local fauna and the assemblage from SDSNH Locality 3486 demonstrate an early Uintan age for the upper part of Member B of the Santiago Formation in northwestern San Diego County. The Murray Canyon local fauna (late early Uintan) is named for a distinctive assemblage from the lower member of the Stadium Conglomerate. The late Uintan Stonecrest local fauna (undifferentiated Stadium Conglomerate) represents the lowest stratigraphic occurrence in San Diego County of several taxa characteristic of the Sespe Formation of Ventura County. The late Uintan Cloud 9 fauna is defined as the entire set of vertebrate taxa present in all outcrops of the Mission Valley Formation.