Guangxicyon, Zhai & Ciochon & Tong & Savage & Morlo & Holroyd & Gunnell, 2003

Zhai, Renjie, Ciochon, Russell L., Tong, Yongsheng, Savage, Donald E., Morlo, Michael, Holroyd, Patricia A. & Gunnell, Gregg F., 2003, An aberrant amphicyonid mammal from the latest Eocene of the Bose Basin, Guangxi, China, Acta Palaeontologica Polonica 48 (2), pp. 293-300 : 294

Family Amphicyonidae Haeckel, 1866 Guangxicyon gen. nov.

[Guangxicynodon nomen nudum Russell and Zhai, 1987]

Type species: Guangxicyon sinoamericanus sp. nov.

Known range: Late Eocene, Bose Basin, Guangxi Province, China.

Diagnosis.—Short−faced amphicyonid with very large c1, small and single−rooted p1–2 and m2–3. No rotation of teeth or crowding of premolars; p3–m1 relatively bunodont and without accessory cusps. Blade of m1 short and set in an oblique direction; metaconid strong and lower than protoconid, equivalent in height to paraconid; large, centrally placed, knob−like hypoconid; entoconid lacking.

Differential diagnosis.— Guangxicyon differs from ursid arctoids (sensu Hunt 1998b) generally in lacking a premasseteric fossa, talonid basin of m1 not labially closed by a prehypocristid (hypoconid crest of Hunt, 1998b), and in the apparent absence of entoconid and entoconulid on m1. Guangxicyon differs from Oligocene ursids in lacking a posterior accessory cusp in p4. Guangxicyon differs from the Early Oligocene and the earliest ursid (sensu Hunt 1998b) Amphicynodon (see Cirot and de Bonis 1992), in being larger and having m1 much more blunt. Guangxicyon differs from the Late Oligocene and Early Miocene earliest hemicyonine ursid Cephalogale (see de Beaumont 1965) in being larger, having the paracone of m1 longer relative to the length of the protoconid, and the metaconid placed less posteriorly. Besides its unique tooth morphology with single−rooted p1, p2, m2, and m3, Guangxicyon differs from the late Middle Eocene supposed amphicyonid Simamphicyon (see e.g., Crochet 1988) in being much larger, having the m1 trigonid much more stout, and the m1 talonid relatively longer. Guangxicyon differs from other short−faced Paleogene amphicyonids (e.g., Brachycyon , Haplocyon ) in the shorter, blunter, and less compressed p3–m1 and the centrally placed hypoconid of m1 talonid. Guangxicyon differs from all Oligocene amphicyonids in lacking the posterior accessory cusp in p4. Guangxicyon shares the structure of m1 trigonid with the Oligocene amphicyonids Brachycyon and Haplocyon . Moreover, it shares its peculiar talonid morphology with the amphicyonid Pseudocyonopsis (see e.g., Kuss 1965; Ginsburg 1966).

Etymology.— Guangxicyon , dog−like mammal from Guangxi; sinoamericanus , a commemorative name referring to the cooperative research project between vertebrate paleontologists from China and America.