Bone crushing jaws.
That’s what they say about the mighty and ferocious ‘bear-dog’ Amphicyon (Fig. 1). Unfortunately only one species (Amphicyon longiramus) of four tested bear-dogs actually nests with dogs and wolves in the large reptile tree (LRT, 1348 taxa). Two (Amphicyon galushi and A. idoneus) nest with the hyaena (genus: Crocuta). A fourth nests with Thylophorops, a carnivorous marsupial we looked at a few days ago here.
Amphicyon longiramus (Lartet 1836, Blainville 1841; Mid-Miocene to Pliocene, 16–9mya; up to 2.5m) is the wide ranging bone-crushing, bear-dog. This is a wastebasket taxon with some specimens (A. longiramus) related to dogs, others (A. galushi) related to hyaenas, while still others (lower right above) nesting with carnivorous marsupials, traditionally considered creodonts.
?Amphicyon idoneus (YPM VP.013134) was originally considered a bear dog, but here nests with A. galushi a type of hyaena.
From what I can gather
there are several dozen specimens attributed to Amphicyon. It would make a good PhD dissertation to untangle this wastebasket genus.
Blainville HM 1841. Osteographie et description iconographique des Mammiferes récentes et fossiles (Carnivores) 1, 2 Paris.
Lartet E 1836. Nomenclature des mammife`res et des coquilles qu’il a trouve´s dans un terrain d’eau douce pre`s de Simorre et de Sansan (Gers). Bulletin de la Socie´te´ Ge´ologique de France 7: 217–220.