INTRODUCTION

Amphicyonid carnivorans at the time of the Eocene-Oligocene transition are the oldest known representatives of the family, poised at the threshhold of a Holarctic radiation of marked diversity centered in the Oligocene and Miocene epochs. Amphicyonids, commonly known as “beardogs,” are the large carnivorans of the mid-Cenozoic that, together with the hemicyonine ursids, dominate the carnivore faunas of the northern continents in the Miocene. By the beginning of the Pliocene the amphicyonid-hemicyonine ursid interval has ended, and the dominant large terrestrial carnivores belong to the modern groups familiar to us today, the felids, ursine ursids, and canids.

Although the earliest amphicyonids are found in the late Eocene of both Eurasia and North America, the fossil record is predominantly North American and European. The oldest European (Cynodictis) and North American (Daphoenus) amphicyonids share a derived basicranial anatomy that proclaims a not-too-distant common ancestry in the Eocene.