Perissodactyla, or odd-toed ungulates, is an order of ungulates. The order includes about 17 living species divided into three families: Equidae, Rhinocerotidae (rhinoceroses), and Tapiridae (tapirs). They typically have reduced the weight-bearing toes to three or one of the five original toes, though tapirs retain four toes on their front feet. The nonweight-bearing toes are either present, absent, vestigial, or positioned posteriorly. By contrast, artiodactyls bear most of their weight equally on four or two of the five toes: their third and fourth toes. Another difference between the two is that perissodactyls digest plant cellulose in their intestines, rather than in one or more stomach chambers as artiodactyls, with the exception of Suina, do.
Embolotherium is an extinct genus of brontothere that lived in Mongolia during the late Eocene epoch. It is most easily recognized by a large bony protuberance emanating from the anterior (front) of the skull. This resembles a battering ram, hence the name Embolotherium. The animal is known from about 12 skulls, several jaws, and a variety of other skeletal elements from the Ulan Gochu formation of Inner Mongolia as well as the Ergilin Dzo Formation of Outer Mongolia.
Andrewsarchus, meaning "Andrews' ruler", is an extinct genus of artiodactyl that lived during the Middle Eocene in what is now China. The genus was first described by Henry Fairfield Osborn in 1924 with the type species A. mongoliensis based on a largely complete cranium. A second species, A. crassum, was described in 1977 based on teeth. A mandible, formerly described as Paratriisodon, does probably belong to Andrewsarchus as well. The genus has been historically placed in the families Mesonychidae or Arctocyonidae, or was considered to be a close relative of whales. It is now regarded as the sole member of its own family, Andrewsarchidae, and may have been related to entelodonts. Fossils of Andrewsarchus have been recovered from the Middle Eocene Irdin Manha, Lushi, and Dongjun Formations of Inner Mongolia, each dated to the Irdinmanhan Asian land mammal age.
Pakotitanops is a genus of poorly known brontothere represented only by a few tooth fragments. Its fossil dates from the middle Eocene Kuldana Formation, in the Ganda Kas area of Pakistan. Because this species is known only from a few tooth fragments it is difficult to compare it to other species to determine if it is indeed a distinct species and to what other species it is mostly closely related.
Paronychodon was a theropod dinosaur genus. It is a tooth taxon, often considered dubious because of the fragmentary nature of the fossils, which include "buckets" of teeth from many disparate times and places but no other remains, and should be considered a form taxon.
Eotitanops is an extinct genus of brontothere native to North America and Asia.
Megacerops is an extinct genus of the prehistoric odd-toed ungulate family Brontotheriidae, an extinct group of rhinoceros-like browsers related to horses. It was endemic to North America during the Late Eocene epoch, existing for approximately 4.1 million years.
Protitanops curryi is an extinct species of brontothere that lived during the Eocene, in the Western United States, especially in Death Valley, California, where the best specimens of the species P. curryi have been found. It bore a strong resemblance to Megacerops brontotheres with its knob-shaped horns. However, the position of the horns differed in Protitanops, in that they pointed straight up, rather than more forwards, like in Megacerops.
Brachydiastematherium transylvanicum is the westernmost species of brontothere, with the first fossils of it being found in Transylvania, Romania. In comparison with other brontothere fossils, it is suggested that B. transylvanicum would have had an elongated head, not unlike Dolichorhinus, and be about 2 meters at the withers.
The Irdin Manha Formation is a geological formation from the Eocene located in Inner Mongolia, China, a few kilometres south of the Mongolian border.
Brontotheriidae is a family of extinct mammals belonging to the order Perissodactyla, the order that includes horses, rhinoceroses, and tapirs. Superficially, they looked rather like rhinos with some developing bony nose horns, and were some of the earliest mammals to have evolved large body sizes of several tonnes. They lived around 56–34 million years ago, until the very close of the Eocene. Brontotheres had a Holarctic distribution, with the exception of Western Europe: they occupied North America, Asia, and Eastern Europe. They were the first fossilized mammals to be discovered west of the Mississippi, and were first discovered in South Dakota.
Balochititanops is an extinct genus of brontotheriid perissodactyl from late Early Eocene deposits of Pakistan. Balochititanops is known from the holotype GSP-UM 6532, right maxilla with teeth, from Kingri area, Balochistan. Many referred materials are known and include cranial and postcranial remains. All specimens were collected from numerous localities in Balochistan and northwestern Frontier Province, from the uppermost part of the Ghazij Formation. It was first named by Pieter Missiaen, Gregg F. Gunnell and Philip D. Gingerich in 2011 and the type species is Balochititanops haqi. It represents one of the oldest Asian brontotheres.
Diplacodon is a genus of prehistoric odd-toed ungulates in the family Brontotheriidae. It was the size of a rhinoceros, with the last two upper premolars molar-like.
Urtinotherium is an extinct genus of paracerathere mammals. It was a large animal that was closely related to Paraceratherium, and found in rocks dating from the Late Eocene to Early Oligocene period. The remains were first discovered in the Urtyn Obo region in Inner Mongolia, which the name Urtinotherium is based upon. Other referred specimens are from northern China.
The Washakie Formation is a geologic formation in northern Colorado and southern Wyoming. It preserves many mammal, bird, reptile and other fossils dating back to the Lutetian stage of the Eocene within the Paleogene period. The sediments fall in the Bridgerian and Uintan stages of the NALMA classification.
The Santiago Formation is a geologic formation in Orange and northwestern San Diego County, California. The siltstones, mudstones and sandstones of the formation preserve fossils of Walshina esmaraldensis and Diegoaelurus vanvalkenburghae, dating back to the Late Eocene to Late Oligocene periods.
Systemodon is a genus of early Eocene mammal of Wasatchian age. It was one of many mammals originally considered the earliest horses, long classified in the genus Hyracotherium. These were dog-sized animals that in life would have looked vaguely like a paca, mara, or chevrotain The type species, S. tapirinus, is represented by 24 individuals from a locale called the Castillo pocket in the Huerfano Formation of Colorado. This well-preserved deposit allows researchers to reconstruct aspects of the environment and lifestyle of the species.
Uintasorex is a genus of primate which lived in North America during the Eocene epoch. Fossils belonging to Uintasorex have been dated to the Bridgerian and Uintan stages, roughly 50.3 to 42 million years ago.
Nanotitanops is an extinct genus of Brontothere from the middle Eocene of China. It contains a single species, N. shanghuangensis. It is known only from isolated teeth, the smallest of any known Brontothere.
The Ergilin Dzo Formation, is a geologic formation in southeastern Mongolia. It preserves fossils of a wide variety of animals, which date back to the late Eocene epoch. The type fauna of the Ergilian Asian land mammal age is defined by the mammalian fossils of this formation.
