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| Notohippidae Temporal range: | |
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| Skull of Eomorphippus bondi | |
Scientific classification  | |
| Domain: | Eukaryota |
| Kingdom: | Animalia |
| Phylum: | Chordata |
| Class: | Mammalia |
| Order: | † Notoungulata |
| Clade: | † Eutoxodontia |
| Family: | † Notohippidae Ameghino, 1894 |
| Genera | |
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Notohippidae is a paraphyletic extinct family of notoungulate mammals from South America. Notohippids are known from the Eocene and Oligocene epochs. [1]
Although the name notohippids means "southern horses," these animals did not resemble horses. The name refers to their teeth, which were very similar to those of horses, featuring sharp incisors and high-crowned molars suitable for shredding grass. The shape of the skull and, particularly, the dentition is the result of convergent evolution with the equids, perissodactyl mammals that developed on the northern continents. The body of notohippids was rather stocky, supported by relatively elongated legs equipped with claws (and not hooves). The earliest forms of notohippids possessed low-crowned molars, but over the course of evolution, the teeth gradually became more prismatic, and covered with a thick layer of cement. The skull also became longer, and as a result of this elongation, spaces formed between the incisors, canines and molars.
The notohippid family was first described by Florentino Ameghino in 1894. The first notohippids developed during the Lower Eocene, Pampahippus arising from ancestors likely found in the archaic families Isotemnidae or Oldfieldtomasiidae. Later, over the course of the Oligocene, more specialized forms emerged, including Notohippus , Rhynchippus Eurygenium , Eomorphippus , Morphippus , Mendozahippus , Pascualihippus , Argyrohippus . One of the last forms attributed to this family, the large Colpodon from the Lower Miocene, is likely a probable aberrant representative of the family Leontiniidae.
The notohippids are part of the notoungulates, a large group of South American mammals that developed various forms of different appearances andsizes over the course of the Cenozoic. The notohippids, in particular, belong to the toxodont group, of which they are considered among the most basal members. Recent studies, however, indicate that the notohippid family is not a monophyletic group, but rather paraphyletic and therefore invalid in a cladistic sense, as it consists of increasingly evolved forms that are closer to the origins of other notoungulate groups.
Notoungulata is an extinct order of ungulates that inhabited South America from the early Paleocene to the end of the Pleistocene, living from approximately 61 million to 11,000 years ago. Notoungulates were morphologically diverse, with forms resembling animals as disparate as rabbits and rhinoceroses. Notoungulata are the largest group of South American native ungulates, with over 150 genera in 14 families having been described, divided into two major subgroupings, Typotheria and Toxodontia. Notoungulates first diversified during the Eocene. Their diversity declined from the late Neogene onwards, with only the large toxodontids persisting until the end of the Pleistocene, perishing as part of the Late Pleistocene megafauna extinctions along with most other large mammals across the Americas. Collagen sequence analysis suggests that notoungulates are closely related to litopterns, another group of South American ungulates, and their closest living relatives being perissodactyls, including rhinoceroses, tapirs and equines as part of the clade Panperissodactyla. However their relationships to other South American ungulates are uncertain. Several groups of notoungulates separately evolved ever-growing cheek teeth.
Toxodontia is a suborder of the meridiungulate order Notoungulata. Most of the members of the five included families, including the largest notoungulates, share several dental, auditory and tarsal specializations. The group is named after Toxodon, the first example of the group to be discovered by science.
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 Deseado and Sarmiento Formations of Argentina and the Salla Formation of Bolivia.
Agriochoerus is an extinct genus of scansorial herbivore of the tylopod family Agriochoeridae, endemic to North America. Agriochoerus and other agriochoerids possessed claws, which is rare within Artiodactyla, as well as likely being scansorial. Agriochoerus was first described in 1869.
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.
Pseudhyrax is an extinct genus of archaeohyracid notoungulate. It lived from the Late Eocene to the Early Oligocene, of what is now South America.
Argyrohippus is an extinct genus of notoungulate, belonging to the family Notohippidae. It lived from the Late Oligocene to the Early Miocene, and its fossilized remains were found in South America.
Periphragnis is an extinct genus of isotemnid notoungulates that lived from the Middle Eocene to the Early Oligocene in what is now Argentina and Chile.
Eomorphippus is an extinct genus of notohippid notoungulate that lived from the Late Eocene to the Early Oligocene 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.
Morphippus is an extinct genus of notohippid notoungulate that lived during the Middle to Late Oligocene in what is now South America.
Archaeopithecus is an extinct genus of notoungulate, belonging to the suborder Typotheria. It lived during the Middle Eocene, in what is today Argentina.
Oldfieldthomasia is an extinct genus of notoungulate, probably related to the suborder Typotheria. It lived during the Middle Eocene, in what is today South America.
Santiagorothia is an extinct genus of interatheriid notoungulate. It lived during the Early Oligocene, and its fossils were discovered in Argentina and Chile.
Cochilius is an extinct genus of interatheriid notoungulate that lived between the Late Oligocene and the lower Miocene in what is now Argentina.
Notopithecus is an extinct genus of Notoungulate, belonging to the suborder Typotheria. It lived from the Middle to the Late Eocene and its fossilized remains were discovered in South America.
Pascualihippus is an extinct genus of notoungulate belonging to the family Notohippidae. It lived during the Late Oligocene, in what is now Bolivia.
Teushentherium is an extinct genus of notohippid notoungulate from the Oligocene of Argentina. Fossils have been found in the Sarmiento Formation of Argentina.
Rosendo is an extinct genus of notohippid notoungulates that lived during the Early Oligocene in what is now Argentina and Chile. Fossils of this genus have been found in the Sarmiento Formation and the Abanico Formations of Argentina and Chile.
Moqueguahippus is an extinct genus of notohippid notoungulates that lived during the Late Oligocene of what is now Peru. Fossils of this genus have been found in the Moquegua Formation of Peru, which it was named after.
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