Oxyaenidae

Oxyaena ("sharp hyena") is an extinct genus of placental mammals from extinct subfamily Oxyaeninae within extinct family Oxyaenidae, that lived in Europe, Asia and North America (with most specimens being found in Colorado) during the early Eocene.

Machaeroides ("dagger-like") is an extinct genus of sabre-toothed predatory placental mammals from the extinct subfamily Machaeroidinae within the extinct family Oxyaenidae, that lived in North America (Wyoming) from the early to middle Eocene.

Oxyaenidae ("sharp hyenas") is a family of extinct carnivorous placental mammals. Traditionally classified in order Creodonta, this group is now classified in its own order Oxyaenodonta ("sharp tooth hyenas") within clade Pan-Carnivora in mirorder Ferae. The group contains four subfamilies comprising fourteen genera. Oxyaenids first appeared during the late Paleocene in North America, with smaller radiations of oxyaenids in Eurasia occurring during the Eocene.

Sarkastodon ("flesh-tearing tooth") is an extinct genus of placental mammals from the extinct subfamily Oxyaeninae within the extinct family Oxyaenidae. The genus lived in Asia (in today's China and Mongolia) during the middle Eocene and was the last known oxyaenid. The first fossil of Sarkastodon, part of a lower jaw, was discovered in 1928 in one of the Central Asiatic Expeditions. The second, consisting of the front of the skull and two partial lower jaws, was discovered by a surgeon, Dr. A. Z. Garber, in the final expedition, two years later. Recognised as a "relatively colossal" oxyaenid,

Patriofelis ("father of cats") is an extinct genus of carnivorous placental mammals from the extinct subfamily Oxyaeninae within the extinct family Oxyaenidae, which lived from the early to middle Eocene, during the Bridgerian stage of NALMA. The first remains were discovered in 1869 by geologist Ferdinand Vandeveer Hayden, and the genus was named the following year by Joseph Leidy. Over the next few decades, additional specimens would be named from the same locality (or similar ones), many assigned to genera of their own or to separate species within Patriofelis. Now, only two are recognised:

Palaeonictis ("ancient weasel") is an extinct genus of placental mammals from extinct subfamily Palaeonictinae within extinct family Oxyaenidae, that lived in Europe and North America from the late Paleocene to the early Eocene.

Apataelurus ("false cat") is an extinct genus of saber-toothed placental mammals from the extinct family Oxyaenidae, that lived in North America and East Asia during the Middle Eocene, 45-42 million years ago. This genus was defined by teeth that were well-adapted to a carnivorous diet. A distinct feature described was a long upper canine tooth that resembled a saber tooth. There are two species currently described: Apataelurus kayi, the type species, and Apataelurus pishigouensis, discovered in 1986.

Malfelis is an extinct genus of carnivorous placental mammals from the extinct subfamily Oxyaeninae, within the extinct family Oxyaenidae. It is from western North America of early Bridgerian Land Mammal Age (Eocene). The type species, Malfelis badwaterensis, is the only known species of the genus.

Diegoaelurus ("San Diego's cat") is an extinct genus of placental mammals from the extinct subfamily Machaeroidinae within the extinct family Oxyaenidae. This genus contains only one species, Diegoaelurus vanvalkenburghae, which was found in the Santiago Formation in California. This mammal lived during the Uintan stage of the Middle Eocene Epoch around 43 to 42 million years ago.

Tytthaena ("little hyena") is an extinct genus of placental mammals from extinct subfamily Tytthaeninae within extinct family Oxyaenidae, that lived in North America from the late Paleocene to early Eocene.