Data from: Whence the beardogs? Reappraisal of the middle to late Eocene “(Miacis)” from Texas, USA, and the origin of Amphicyonidae (Mammalia, Carnivora)

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 as *Miacis cognitus* and *M. 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 genera *Gustafsonia* and *Angelarctocyon*,
respectively. These two taxa fill in some of the morphological gaps between
the previously 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 middle Eocene. Their precise
geographic origin remains uncertain, but it is plausible that southern
North America served as an important stage for a very early phase of
amphicyonid radiation.