The Oligocene is a geologic epoch of the Paleogene Period and extends from about 33.9 million to 23 million years before the present. As with other older geologic periods, the rock beds that define the epoch are well identified but the exact dates of the start and end of the epoch are slightly uncertain. The name Oligocene was coined in 1854 by the German paleontologist Heinrich Ernst Beyrich from his studies of marine beds in Belgium and Germany. The name comes from the Ancient Greek ὀλίγος and καινός, and refers to the sparsity of extant forms of molluscs. The Oligocene is preceded by the Eocene Epoch and is followed by the Miocene Epoch. The Oligocene is the third and final epoch of the Paleogene Period.
Castoridae is a family of rodents that cointains the two living species of beavers and their fossil relatives. A formerly diverse group, only a single genus is extant today, Castor. Two other genera of "giant beavers", Castoroides and Trogontherium, became extinct in the Late Pleistocene.
Nothofagus, also known as the southern beeches, is a genus of 43 species of trees and shrubs native to the Southern Hemisphere in southern South America and east and southeast Australia, New Zealand, New Guinea, and New Caledonia. The species are ecological dominants in many temperate forests in these regions. Some species are reportedly naturalised in Germany and Great Britain. The genus has a rich fossil record of leaves, cupules, and pollen, with fossils extending into the late Cretaceous period and occurring in Australia, New Zealand, Antarctica, and South America.
Sciuromorpha is a rodent clade that includes several different rodent families. It includes all members of the Sciuridae as well as the mountain beaver species.
Steneofiber is an extinct genus of beavers from the Miocene. They contain several species of beavers. Amongst them are S.barbouri, S.complexus, S.depereti, S.fossor, S.gradatus, and S.hesperus. Their various species are found all the way from the eastern end of the Iberian peninsula to southern Japan. S.depereti has been found in northwest Germany.
Daphoenus is an extinct genus of amphicyonids. Daphoenus inhabited North America from the Middle Eocene to the Middle Miocene, 37.2—16.0 Mya, existing for approximately 21 million years.
The zygomasseteric system in rodents is the anatomical arrangement of the masseter muscle of the jaw and the zygomatic arch of the skull. The anteroposterior or propalinal (front-to-back) motion of the rodent jaw is enabled by an extension of the zygomatic arch and the division of the masseter into a superficial, lateral and medial muscle. The four main types are described as protrogomorphous, sciuromorphous, hystricomorphous, and myomorphous.
The Eocene–Oligocene extinction event, also called the Eocene-Oligocene transition or Grande Coupure, is the transition between the end of the Eocene and the beginning of the Oligocene, an extinction event and faunal turnover occurring between 33.9 and 33.4 million years ago marked by large-scale extinction and floral and faunal turnover. Most of the affected organisms were marine or aquatic in nature. They included the last of the ancient ungulates, the "condylarths".
Castor californicus is an extinct species of beaver that lived in western North America from the end of the Miocene to the early Pleistocene. Castor californicus was first discovered in Kettleman Hills in California, United States. The species was similar to but larger than the extant North American beaver, C. canadensis.
Anchitheriomys is an extinct member of the beaver family, Castoridae. It inhabited North America and Eurasia during the middle Miocene. The name of the genus comes from Anchitherium, an extinct genus of horses, and the Greek word for mouse, μῦς (mys), thus meaning "Anchitherium's mouse", because the fossils of both genera usually co-occur.
Propalaeocastor is a poorly known extinct genus of beavers from the early Oligocene of Europe and Asia. Recently described material of a new species of Propalaeocastor, P. irtyshensis, indicates the genus is probably the earliest known member of the subfamily Castorinae, which includes all castorids more closely related to living beavers than to the extinct giant beaver. Previously, Propalaeocastor had been allied with more basal beavers such as Agnotocastor and Anchitheriomys. According to Wu and coauthors, Propalaeocastor, specifically P. butselensis, is the likely ancestor of the better-known Eurasian castorine Steneofiber.
Migmacastor is an extinct member of the beaver family, Castoridae, known from a single species, Migmacastor procumbodens. Only a single specimen has been reported, a skull from the late Oligocene or early Miocene of Nebraska. Features of the incisor teeth of Migmacastor indicate they were used to dig. Other extinct beavers, including the better-known Palaeocastor, were also fossorial (digging), but Migmacastor may have become a burrower independently.
Ashorocetus is a monotypic genus of an extinct primitive baleen whale of the family Aetiocetidae. It was named by Barnes et al. 1995, and contains one species, A. eguchii. Fossils of this whale are found from the Chattian Morawan formation, near Ashoro, of upper Oligocene Hokkaido, Japan. Ashorocetus eguchii was described based on a partial skull and is named after the type locality and Kenichiro Eguchi of the Ashoro Museum of Paleontology.
Parapithecus is an extinct genus of primate that lived during the Late Eocene-Earliest Oligocene in what is now Egypt. Its members are considered to be basal anthropoids and the genus is closely related to Apidium. There are two known species. They lived about 40 to 33 million years ago.
Spathorhynchus is an extinct genus of amphisbaenians or worm lizards that existed from the Middle Eocene to the Early Oligocene in what is now Wyoming. It includes two species, the type species S. fossorium, named in 1973 from the Middle Eocene Bridger and Wind River Formations, and the species S. natronicus, named in 1977 from the Lower Oligocene White River Formation. Spathorhynchus belongs to the family Rhineuridae, which includes many other extinct species that ranged across North America at various times in the Cenozoic but only has one surviving member, Rhineura floridana, from Florida. Spathorhynchus differs from all other rhineurids except Dyticonastis from the Late Oligocene-Early Miocene of Oregon in having a slightly widened, spatula-shaped snout tip with a low angle of about 30 degrees. The two taxa may be closely related, having evolved in isolation in western North America after the formation of the Rocky Mountains separated them from rhineurids further east.
Diegoaelurus is an extinct genus of placental mammals from extinct the subfamily Machaeroidinae within 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 46.2 to 39.7 million years ago.
Prosotherium is an extinct genus of hegetotheriid notoungulate. It lived during the Late Oligocene, and its fossilized remains were found in South America.
Propachyrucos is an extinct genus of hegetotheriid notoungulate. It lived from the Late Oligocene to the Early Miocene, in what is today South America.
Eurygenium is an extinct genus of notoungulate belonging to the family Notohippidae. It lived during the Late Oligocene in what is today South America.
Taubatherium is an extinct genus of mammal, belonging to the order Notoungulata. It lived during the Late Oligocene, in what is today Brazil, in South America.
