A skull of the immigrant Eurasian beardog Cynelos (Carnivora, Amphicyonidae) from the early Miocene of southern California

Abstract

ABSTRACT—At ∼23 Ma, large amphicyonid carnivorans participated in the initial Neogene mammal migration passing though the Bering filter en route to North America. Among the migrants were the amphicyonines Cynelos and Ysengrinia, first appearing in early Miocene sediments of the upper Arikaree Group in Nebraska and Wyoming, having entered the New World with chalicotheres, small cervoids, and the cursorial rhinoceros Menoceras. Early representatives of these immigrant carnivores had not, until recently, been recovered from localities along the Pacific coastal corridor of western North America. Here we report the discovery of a unique skull that establishes the presence of an early Neogene species of Cynelos (C. malasi, sp. nov.) in coastal southern California. The skull shares craniodental features with early Miocene species of the genus in Europe. Dentition (P4-M1-M2) and cranial morphology of Cynelos malasi compare with C. helbingi (southern Germany) and C. lemanensis (France, Germany) but uniquely combine size and occlusal detail to preclude assignment to these species. Cynelos malasi is assigned a latest Arikareean (Ar4) age in the North American Land Mammal Age (NALMA) chronology. By the early Miocene, species of Cynelos had dispersed from western Europe to northern Africa and into western North America. Whether the taxon arrived in North America by following a coastal southern Asian route or by Palaearctic dispersal is unconfirmed. Given the similarity between North American and European species of Cynelos, we suspect that the genus spanned Asia during the early Miocene.

http://zoobank.org/urn:lsid:zoobank.org:pub:6F78C042-8C98-47B3-BFD0-E6943A615197

ACKNOWLEDGMENTS

We thank the Archaeological and Paleontological Cooper Center and Curator M. Rivin, Department of Geological Sciences, University of California–Fullerton, for the loan of OCPC 21791, and for the encouragement of the late J. D. Cooper in the initiation of the study. The skull was capably prepared by H. Thomas, Natural History Museum of Los Angeles County, and was first recognized as Cynelos by H. M. Wagner, San Diego Natural History Museum. E. B. Lander, Paleo Environmental Associates, Altadena, California, provided information on the site of collection of C. malasi and on stratigraphy at the Windy Ridge locality as well as discussion of mammals from relevant OCPC mitigation sites. The senior author is grateful to the curators of North American, European, and Kenyan museums and universities listed in this report for access to specimens and comparative material that contributed to analysis of OCPC 21791. S. Peigné, Muséum National d’Histoire naturelle, Paris, provided helpful advice and insight during the study, and casts of Cynelos from Selles-sur-Cher, France. Figures were prepared or modified by A. S. Fox, UNSM Scientific Illustrator. The authors particularly thank L. de Bonis, S. Viranta, and B. Van Valkenburgh for useful reviews of the manuscript.

Handling editor: Blaire van Valkenburgh.