Amphicyon is an extinct genus of large carnivorans belonging to the family Amphicyonidae (known colloquially as "bear-dogs"), subfamily Amphicyoninae, from the Miocene epoch. Members of this family received their vernacular name for possessing bear-like and dog-like features. They ranged over North America, Europe, Asia, and Africa.
In a note dated back to May 16, 1836, French geologist Alexandre Leymerie wrote of a letter in April that he requested from French palaeontologist Édouard Lartet, which provided details of his exploits in palaeontological sites in the French department of Gers, in particular the commune Sansan. Lartet described his finds of fossil taxons that he found within the sites, including "Mastodonte" (species assigned to it were later reclassified to another mammutid Zygolophodon and the gomphothere Gomphotherium), "Dinotherium" (its species eventually reclassified as either Deinotherium or Prodeinotherium), "Rhinoceros" (reclassified as an aceratherine rhinocerotid Hoploaceratherium), and "Palaeotherium" (the referred equid species now known as belonging to an anchitherine Anchitherium). He also recalled finding fossil "deer" species of which he said that the largest ones were the size of extant deer in France while the smallest ones were the size of small antelope. The palaeontologist noted that the "peaceful ruminants" coexisted with a "formidable" large carnivore he provisionally named Amphicyon based on two half-jaws and bones that he sent to a museum. He described it as having unilobed incisors and compressed canines similar to raccoons but also a carnivorous molar and its first two tubercles conforming those to dogs. Lartet then stated that the genus's most distinct trait was the existence of a third tubercle at the upper jaw, which was not known in any other carnivore. The genus name appears to be derived from the Ancient Greek terms ἀμφί ("on both sides") and κύων ("dog"), but Lartet did not define the genus's etymology.[1]
Despite the initial status of the genus name Amphicyon as nonpermanent, French anatomist Henri Marie Ducrotay de Blainville, a peer who Lartet had regularly discussed his fossil findings with, had sketched mammal skeletons and fossils in 1841, where he recognized the 2 species "Amphicyon major" and "Amphicyon? minor."[1][2] In 1851, Lartet reviewed the fossil carnivoran genera from Sansan. Among them were Amphicyon, in which it was reconfirmed as a carnivorous mammal the size of extant bears that was discovered in Sansan in 1835. He recalled that its single-lobed incisors and its canines of serrated ridges are similar to the raccoon while the molars were similar to that of a dog. He confirmed the fossil specimens along with the third tubercle in the upper jaw (of which he said that it only exists in the extant bat-eared fox (then known as "Canis megalotis")) as belonging to the species Amphicyon major. The palaeontologist described it as also having an anatomy of plantigrade locomotion similar to extant bears with few differences in form. Blainville was mentioned as speculating that it must have had a long and very strong tail. The species "Amphicyon minor" was reclassified as a separate genus Hemicyon, which he described as a carnivore larger than a European wolf that was closer in form to a dog than Amphicyon and had dentition similar to mustelids. He also described a newer genus Pseudocyon, which he misidentified as being digitigrade and described as being smaller than Amphicyon and coming closest to canids based on its dentition and bones. All three genera, Lartet said, had canines that retained finely serrated edges, implying that they were some of the top coexisting predators of the Miocene in modern-day France.[3]