title: Whence the beardogs? Reappraisal of the Middle to Late Eocene 'Miacis' from Texas, USA, and the origin of Amphicyonidae (Mammalia, Carnivora).
abstract: The Middle to Late Eocene sediments of Texas have yielded a wealth of fossil material that offers a rare window on a diverse and highly endemic mammalian fauna from that time in the southern part of North America. These faunal data are particularly significant because the narrative of mammalian evolution in the Paleogene of North America has traditionally been dominated by taxa that are known from higher latitudes, primarily in the Rocky Mountain and northern Great Plains regions. Here we report on the affinities of two peculiar carnivoraforms from the Chambers Tuff of Trans-Pecos, Texas, that were first described 30 years ago asMiacis cognitusandM. australis. Re-examination of previously described specimens and their inclusion in a cladistic analysis revealed the two taxa to be diminutive basal amphicyonids; as such, they are assigned to new generaGustafsoniaandAngelarctocyon, respectively. These two taxa fill in some of the morphological gaps between the earliest-known amphicyonid genus,Daphoenus, and other Middle-Eocene carnivoraforms, and lend additional support for a basal caniform position of the beardogs outside the Canoidea. The amphicyonid lineage had evidently given rise to at least five rather distinct forms by the end of the Middle Eocene. Their precise geographical origin remains uncertain, but it is plausible that southern North America served as an important stage for a very early phase of amphicyonid radiation.
authors.affiliation: Integrative Research and Ganz Family Collections Centers, Field Museum of Natural History, Chicago, IL 60605, USA; University of California Museum of Paleontology, Berkeley, CA 94720, USA.
authors.forename: Susumu
authors.identifier: 0000-0001-6038-899X
authors.initials: S
authors.lastname: Tomiya
authors.affiliation: Division of Paleontology, American Museum of Natural History, New York, NY 10024, USA; Department of Pathology and Anatomical Sciences, Jacobs School of Medicine and Biomedical Sciences, University at Buffalo, Buffalo, NY 14214, USA.
authors.forename: Zhijie Jack
authors.identifier: 0000-0001-5335-4230
authors.initials: ZJ
authors.lastname: Tseng
keywords: Amphicyonidae; Caniformia; Carnivora; Miacis; Middle Eocene; phylogeny