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.
The Proboscidea are a taxonomic order of afrotherian mammals containing one living family (Elephantidae) and several extinct families. First described by J. Illiger in 1811, it encompasses the elephants and their close relatives. From the mid-Miocene onwards, most proboscideans were very large. The largest land mammal of all time may have been a proboscidean; Palaeoloxodon namadicus was up to 5.2 m (17.1 ft) at the shoulder and may have weighed up to 22 t, almost double the weight of several sauropods including Diplodocus carnegii and Apatosaurus louisae. The largest extant proboscidean is the African bush elephant, with a record of size of 4 m (13.1 ft) at the shoulder and 10.4 t. In addition to their enormous size, later proboscideans are distinguished by tusks and long, muscular trunks, which were less developed or absent in early proboscideans.
A mastodon is any proboscidean belonging to the extinct genus Mammut that inhabited North and Central America during the late Miocene or late Pliocene up to their extinction at the end of the Pleistocene 10,000 to 11,000 years ago. Mastodons lived in herds and were predominantly forest-dwelling animals that lived on a mixed diet obtained by browsing and grazing, somewhat similar to their distant relatives, modern elephants, but probably with greater emphasis on browsing.
Deinotheriidae is a family of prehistoric elephant-like proboscideans that lived during the Cenozoic era, first appearing in Africa, then spreading across southern Asia (Indo-Pakistan) and Europe. During that time, they changed very little, apart from growing much larger in size; by the late Miocene, they had become the largest land animals of their time. Their most distinctive features were the downward-curving tusks on the lower jaw.
Chilgatherium is the earliest and most primitive representative of the family Deinotheriidae. It is known from late Oligocene fossil teeth found in the Ethiopian district of Chilga.
Paraceratherium is an extinct genus of hornless rhinoceros. It is one of the largest terrestrial mammals that has existed and lived from the early to late Oligocene epoch. The first fossils were discovered in what is now Pakistan, and remains have been found across Eurasia between China and the Balkans. It is classified as a member of the hyracodont subfamily Indricotheriinae. Paraceratherium means "near the hornless beast", in reference to Aceratherium, the genus in which the type species A. bugtiense was originally placed.
Oligopithecus is a fossil primate that lived in Africa during the Early Oligocene. It is represented by one species, Oligopithecus savagei, known from one jaw bone found in Egypt.
Tethytheria is a clade of mammals that includes the sirenians and proboscideans, as well as the extinct order Embrithopoda.
The genus Apidium is that of at least three extinct primates living in the early Oligocene, roughly 30 million years ago. Apidium fossils are common in the Fayoum deposits of Egypt. Fossils of the earlier species, Apidium moustafai, are rare; fossils of the later species Apidium phiomense are fairly common.
Pyrotherium is an extinct genus of South American ungulate, of the order Pyrotheria, that lived in what is now Argentina and Bolivia, during the Late Oligocene. It was named Pyrotherium because the first specimens were excavated from an ancient volcanic ash deposit. Fossils of the genus have been found in the Sarmiento Formation of Argentina and the Salla Formation of Bolivia.
Numidotheriidae is an extinct family of primitive proboscidean that lived from the late Paleocene to the early Oligocene periods of North Africa.
Barytherium is a genus of an extinct family (Barytheriidae) of primitive proboscideans that lived during the late Eocene and early Oligocene in North Africa. The type species is Barytherium grave, found at the beginning of the 20th century in Fayum, Egypt. Since then, more complete specimens have been found at Dor el Talha, Libya. More fossils were also discovered in 2011 in the Aidum area in Dhofar by Oman's Ministry of Heritage and Culture, which was named Barytherium omansi.
Eritreum melakeghebrekristosi is an extinct species of proboscidean mammal, which lived in Northeast Africa during the late Oligocene some 27 million years ago, and is considered to be the missing link between modern elephants and their ancestors. The fossils of this species are the oldest known fossils featuring the horizontal tooth displacement seen in modern elephants. The species is estimated to have weighed 484 kg (1,067 lb) and stood about 1.3 m (4.3 ft) at the shoulder, much smaller than modern species.
Jeheskel "Hezy" Shoshani was an evolutionary biologist who studied elephants and their relatives for over 35 years.
Paraentelodon is an extinct entelodont from the Late Oligocene and Oligocene-Miocene boundary of Asia. The fossils of the type species P. intermedium were found in Georgia, Kazakhstan and China. An indeterminate species represents in Bugti Hills which is the late Oligocene of Pakistan.
Stegodontidae is an extinct family of Stegodon-like proboscideans that was endemic to Africa and Asia from the Miocene (15.97 mya) to the Late Pleistocene, with some studies suggesting that some survived into the Holocene in China, although this is disputed.
Propliopithecoidea is a superfamily of catarrhine primates that inhabited Africa and Arabia during the Early Oligocene about 32 to 29 million years ago. Fossils have been found in Egypt, Oman and Angola. They are one of the earliest known families of catarrhines.
Arcanotherium is an extinct genus of early proboscidean belonging to the family Numidotheriidae that lived in north Africa during the late Eocene/early Oligocene interval.
Omantherium is a genus of an extinct genus of barytheriid proboscidean that lived during the early Oligocene in Oman. It belongs to the family Barytheriidae, which represented the first large size proboscideans to appear in the fossil record and were characterized by a strong sexual dimorphism.
