Not Amphicyon This specimen was attributed to the bear dog genus Amphicyon, but here it nests with Megistotherium. It was a big carnivorous bush dog with large premaxillary teeth.

Megistotherium osteothlastes (Savage 1973; Miocene, 23mya; 66cm skull length) was originally considered a giant hyaenodontid creodont. Here it nests with the much smaller extant bush dog, Speothos. The jaw muscles were enormous. The large diameter canines were housed in large, laterally expanded maxillae. The braincase was narrow.

Side note: In overall size and features, Megistotherium is similar, by convergence, to the giant elephant shrew, Andrewsarchus.

Rich TH, Flannery TF, Trusler P, Kool L, van Klaveren NA and Vickers-Rich P 2001. A second tribosphenic mammal from the Mesozoic of Australia. Records of the Queen Victoria Museum 110: 1-9.

Savage RJ 1973. Megistotherium, gigantic hyaeonodont from Miocene of Gebel Zelten, Libya. Bulletin of the British Museum (Natural History) Geology 22(7):483–511.

wiiki/Megistotherium