''Argyrohippus'' is an extinct

genus Genus ( plural genera ) is a taxonomic rank used in the biological classification of living and fossil organisms as well as viruses. In the hierarchy of biological classification, genus comes above species and below family. In binomial nom ...

notoungulate Notoungulata is an extinct order of mammalian ungulates that inhabited South America from the early Paleocene to the Holocene, living from approximately 61 million to 11,000 years ago. Notoungulates were morphologically diverse, with forms resemb ...

, belonging to the family

Notohippidae Notohippidae is a paraphyly, paraphyletic extinct Family (biology), family of Notoungulata, notoungulate mammals from South America. Notohippids are known from the Eocene and Oligocene Epoch (reference date), epochs.McKenna, Malcolm C., and Bell ...

. It lived from the Late Oligocene to the Early

Miocene The Miocene ( ) is the first epoch (geology), geological epoch of the Neogene Period and extends from about (Ma). The Miocene was named by Scottish geologist Charles Lyell; the name comes from the Greek words (', "less") and (', "new") and mea ...

, and its fossilized remains were found in

South America South America is a continent entirely in the Western Hemisphere and mostly in the Southern Hemisphere, with a relatively small portion in the Northern Hemisphere at the northern tip of the continent. It can also be described as the sout ...

Description

This animal was probably vaguely similar in build and size to a goat. It is mostly known from remains of its dentition, which was very specialized : the dentition was complete and continuous (without diastema), but the premolars and molars were hypsodonts. The canines were small. The premolars had a very developed cingulum, while the molars were quite elongated. The shape of the premolars and molar was very reminiscent of those of

Equidae Equidae (sometimes known as the horse family) is the taxonomic family of horses and related animals, including the extant horses, asses, and zebras, and many other species known only from fossils. All extant species are in the genus '' Equus'', ...

. Its most peculiar distinctive characteristics were the cup-shaped internal cingula and the lack of singula on the premolars, and a thick layer of

cementum Cementum is a specialized calcified substance covering the root of a tooth. The cementum is the part of the periodontium that attaches the teeth to the alveolar bone by anchoring the periodontal ligament.Illustrated Dental Embryology, Histology, ...

Classification

The genus ''Argyrohippus'' (whose name means "Argentine

horse The horse (''Equus ferus caballus'') is a domesticated, one-toed, hoofed mammal. It belongs to the taxonomic family Equidae and is one of two extant subspecies of ''Equus ferus''. The horse has evolved over the past 45 to 55 million yea ...

") was first described in 1902 by

Florentino Ameghino Florentino Ameghino (born Giovanni Battista Fiorino Giuseppe Ameghino September 19, 1853 – August 6, 1911) was an Argentine naturalist, paleontologist, anthropologist and zoologist, whose fossil discoveries on the Argentine Pampas, especially ...

, based on fossil remains found in Early Miocene deposits in

Argentina Argentina (), officially the Argentine Republic ( es, link=no, República Argentina), is a country in the southern half of South America. Argentina covers an area of , making it the second-largest country in South America after Brazil, th ...

. The type species is ''Argyrohippus fraterculus'' ; Ameghino described another species, ''A. boulei'', mainly differentiated from the type species by some dental characteristics, like its more protruding incisors, and by its greater size. In 1935, a new species was described by Bryan Patterson, ''A. praecox'', from the Late Oligocene of Argentina, with more brachydont teeth. ''Argyrohippus'' has historically been classified as a member of

, a group of notoungulates with teeth similar to those of horses. However, this family is now considered paraphyletic, and several forms included in it may in reality be ancestral to the family

Toxodontidae Toxodontidae is an extinct family of notoungulate mammals, known from the Oligocene to the Holocene (11,000 BP) of South America, with one genus, ''Mixotoxodon'', also known from the Pleistocene of Central America and southwestern North America ...

. ''Argyrohippus'' may be one of those forms.

Bibliography

* F. Ameghino. 1902. Première contribution à la connaissance de la fauna mammalogique des couches à Colpodon irst contribution to the knowledge of the mammalian fauna of the Colopdon Beds Boletin de la Academia Nacional de Ciencias de Córdoba 17:71-141 * Patterson, B. 1935. A new Argyrohippus from the Deseado beds of Patagonia. Fieldiana, Geology 6:161–166 * G. M. López, A. M. Ribeiro, and M. Bond. 2010. The Notohippidae (Mammalia, Notoungulata) from Gran Barranca: preliminary considerations. In R. H. Madden, A. A. Carlini, M. G. Vucetich, R. F. Kay (eds.), The Paleontology of Gran Barranca: Evolution and Environmental Change through the Middle Cenozoic of Patagonia 143–151 {{Taxonbar, from=Q60978272 Toxodonts Oligocene mammals of South America Miocene mammals of South America Neogene Argentina Paleogene Argentina Fossils of Argentina Fossil taxa described in 1902 Taxa named by Florentino Ameghino Prehistoric placental genera Golfo San Jorge Basin Sarmiento Formation