Oligocene first appearances

Dromornithidae, known as mihirungs (after Tjapwuring Mihirung paringmal, "giant bird") and informally as thunder birds or demon ducks, is an extinct family of large, flightless birds native to Australia from at least the late Oligocene (and perhaps as early as the early Eocene) to the Late Pleistocene. They were long classified in Struthioniformes (the ratites), but are now usually classified as a type of gigantic fowl (Galloanserae). Dromornithids were part of the Australian megafauna. One species, Dromornis stirtoni, was tall, making them among the largest birds ever. Only a single species,

Teratornithidae is an extinct family of very large birds of prey that lived in North and South America from the Late Oligocene to Late Pleistocene. They include some of the largest known flying birds. Its members are known as teratorns.

Obdurodon is a genus of extinct platypus-like Australian monotreme which lived from the Late Oligocene to the Late Miocene. Three species have been described in the genus, the type species Obdurodon insignis, plus Obdurodon dicksoni and Obdurodon tharalkooschild. Obdurodon appeared much like their modern day relative the platypus, except adults retained their molar teeth, and unlike the platypus, which forages on the lakebed, they may have foraged in the water column or surface.

The extinct Borophaginae form one of three subfamilies found within the canid family. The other two canid subfamilies are the extinct Hesperocyoninae and extant Caninae. Borophaginae, called "bone-crushing dogs", were endemic to North America during the Oligocene to Pliocene and lived roughly 34—2.5 million years ago, existing for about .

Sagittariidae is a family of raptor with one living species—the secretarybird (Sagittarius serpentarius) native to Africa—and a few fossil taxa.

Pampatheriidae (from the Pampas Plain, and Ancient Greek θηρίον (theríon), meaning "beast") is an extinct family of large xenarthran cingulates related to armadillos. They first appeared in South America during the mid-Miocene, and Holmesina and Pampatherium spread to North America during the Pleistocene after the formation of the Isthmus of Panama as part of the Great American Interchange. They became extinct as part of the end-Pleistocene extinction event, about 12,000 years ago.

Kentriodontidae is an extinct family of odontocete whales related to modern dolphins. The Kentriodontidae lived from the Oligocene to the Pliocene before going extinct.

Aceratheriinae (from Ancient Greek ἀ- (á-), meaning "-less", κέρας (kéras), meaning "horn", and θηρίον (theríon), meaning "beast") is an extinct subfamily of true rhinoceroses (Rhinocerotidae) that ranged across Eurasia, Africa and North America from the Oligocene to the beginning of the Pliocene. Members of the group generally lacked horns, though some members of the family may have borne small horns.

The Temnocyoninae are an extinct subfamily of medium-sized amphicyonids endemic to North America that lived during the Early Oligocene to Early Miocene about 30.8-20.43 million years ago (Mya) existing for around 10 million years.

Wynyardiidae is an extinct family of possum-like marsupials from the early Miocene of Wynyard in Tasmania, long been considered to display skeletal features that are intermediate between the primitive polyprotodont and the advanced diprotodont marsupials.