Oligocene mammals

Hyaenodon ("hyena-tooth") is an extinct genus of carnivorous placental mammals from the tribe Hyaenodontini, part of the subfamily Hyaenodontinae (which is within the family Hyaenodontidae), that belonged to the now extinct order Hyaenodonta. The genus was found lived in Eurasia and North America from the Middle Eocene to the Early Miocene, from 38 to 17 million years ago, existing for . Hyaenodon first evolved in Asia, probably evolving from Propterodon.

Embrithopoda ("heavy-footed" in Ancient Greek) is an order of extinct paenungulate mammals known from Asia, Africa and Eastern Europe. Most of the embrithopod genera are known exclusively from jaws and teeth dated from the late Paleocene to the late Eocene; however, the order is best known from its terminal member, the large Arsinoitherium.

Arsinoitheriidae is a family of mammals belonging to the extinct order Embrithopoda. Remains have been found in the Middle East, Africa, Asia and Romania. Arsinotheriids were closely related to hyraxes, elephants, sirenians, and possibly desmostylians (as part of the superorder Afrotheria). The name of the clade honors the wife of Ptolemy II, Queen Arsinoe II of Egypt, as the first fossils of Arsinoitherium were found near the ruins of her palace.

thumb|right|Xotodon sp. skull at the Museum für Naturkunde, Berlin

Hyainailouridae ("hyena-like cats") is a paraphyletic family of extinct predatory mammals within the polyphyletic superfamily Hyainailouroidea within extinct order Hyaenodonta. Fossil records show hyainailourids arose during the Middle Eocene, although Early Eocene origin is suspected, the family persisted into the Late Miocene.'' Fossils of this group have been found in Eurasia, Africa, and North America. ==Classification and phylogeny== ===Relations=== Hyainailouridae used to be considered a subfamily of Hyaenodontidae, but cladistic study by Sole et al.'', (2013, 2015) treats it as a disti

Desmostylidae is an extinct family of herbivorous marine mammals belonging to the order of Desmostylia. They lived in the coastal waters of the northern Pacific Ocean from the Early Oligocene (Rupelian) through the Late Miocene (Tortonian) (33.9 mya—7.2 MYA), existing for approximately .