Amphicyon is an extinct genus of large carnivorans belonging to the family Amphicyonidae (known colloquially as "bear-dogs"), subfamily Amphicyoninae, from the Miocene epoch.

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 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.

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.

[11] One study argued that A. longiramus was hypercarnivorous, as the relative grinding area of its lower molars is similar to that of carnivorous canids, whereas another suggested that the North American species of the genus were omnivores.

[70][7] A dental microwear analysis of A. major recovers the diet of this species as mesocarnivorous, similar to red foxes, consuming meat as well as plants and hard items, which presumably included bone.

[6] As it lacked the adaptations for rapid acceleration, Amphicyon seems to have hunted quite unlike lions and tigers, which approach their prey very closely, before overtaking it after a quick burst of speed.

Its postscapular fossa indicates a well-developed subscapularis minor muscle, which fixes the shoulder joint, and prevents the head of the humerus from being dislocated by the struggles of a prey animal trying to break free.

Indeed, the trochlea of its humeral condyle is shallower than that of a tiger, suggesting that the pronation/supination of its forearms might have been even greater than in large felids, although it likely lacked the ability of cats to retract their claws.

Its small infraorbital foramina indicates that it lacked the well-developed vibrissae of cats, which provides them with the sensory information needed to place a precise killing bite.

Due to its comparatively slow maximum speed and lack of rapid acceleration, it is unlikely that Amphicyon preyed on cursorial ungulates.

Comparison with other strongly sexually dimorphic carnivorans suggests that Amphicyon was polygynous, with territorial males competing with each other for females during the mating season.

[78] Fossil remains of Amphicyon are most common in Western and Central Europe, where they were discovered in various countries, including France, Germany, Spain and Hungary, but were also found in Bosnia-Herzegovina and Turkey.

[23] While common throughout the continent during the Middle Miocene, amphicyonid diversity decreased following the Vallesian Turnover, with the last known European species of the genus surviving in Central Europe until MN11, which dates from 8.7 to 7.75 Ma.

[8][11][13] While various remains and species of Amphicyon have been reported from South and East Asia, their referral is often problematic, as they're usually known from fragmentary material and all large sized amphicyonids found on the continent are generally placed in this genus.

[6] However, it has been proposed that the late Miocene A. lydekkeri from Pakistan, which is sometimes attributed to the separate genus Arctamphicyon, is a descendant of A. zhanxiangi, with the lineage immigrating from Northern China to Southern Asia.

[31][80] A very large humerus from the Manchar formation indicates that a gigantic species was present in the Siwaliks during the early parts of the Middle Miocene.

[33] South East Asian reports include a large incisor from the Aquitanian (~23-21 Ma) of Vietnam, and a species from the Lower Irrawaddy Formation of Myanmar, which is likely closely related to Arctamphicyon.

These remains show morphological differences to A. major, and several of the species to which it had been compared, mostly because of their similar, small size, including A. bohemicus, A. styriacus and A. steinheimensis (which also shares the apomorphic features present in the Arabian taxon), have since been moved to other genera.

It likely gave rise to the larger A. frendens, which itself was ancestral to the huge A. ingens, which was also the last North American member of the genus, disappearing around 14.2 Ma.