Hyainailouridae
Hyainailouridae ("hyena-cats") is a paraphyletic family of extinct predatory mammals from extinct paraphyletic superfamily Hyainailouroidea within extinct order Hyaenodonta. Hyaenodontids arose during the middle Eocene and persisted well into the middle Miocene. Fossils of this group have been found in Asia, Africa, North America and Europe. General characteristics Hyainailourids are characterized by long skulls, slender jaws, slim bodies, and a plantigrade stance. They generally ranged in size from 30 to 140 cm at the shoulder. While some measured as much as 1.4 m high at the shoulder with head-body length up to 3.2 m and weighed up to 1,500 kg, most were in the 5–15 kg range, equivalent to a mid-sized dog. The anatomy of their skulls show that they had a particularly acute sense of smell, while their teeth were adapted for shearing, rather than crushing. At least one hyainailourid lineage, Apterodontinae, was specialised for aquatic, otter-like habits. Range The oldest member of the Hyainailouridae is Orienspterodon from the middle Eocene of China. They were important hypercarnivores in Eurasia and Africa during the Oligocene, but gradually declined, with almost the entire family becoming extinct by the close of the Oligocene. Only Simbakubwa, Megistotherium and several of its sister genera,