''Otrhonia'' 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

Notostylopidae Notostylopidae is an extinct Family (biology), family comprising five genus, genera of Notoungulata, notoungulate mammals known from the Late Paleocene (Riochican) to Early Oligocene (Tinguirirican) of Argentina, Brazil and Chile in South America ...

family. It lived during the Late

Eocene The Eocene ( ) Epoch is a geological epoch that lasted from about 56 to 33.9 million years ago (mya). It is the second epoch of the Paleogene Period in the modern Cenozoic Era. The name ''Eocene'' comes from the Ancient Greek (''ēṓs'', " ...

, and its remains were discovered 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 approximately the size of a modern racoon, and its length may have been around 60–70 centimeters excluding the tail. The skull was 14–15 centimeters long, and the animal may have been close to 10 kilograms. ''Otrhonia'' had a robust and square skull, characterised by its specialized dentition. As well as in some of its relatives, such as ''

Notostylops ''Notostylops'' ("south pillar face") is a genus of extinct South American ungulates from Eocene Argentina. Fossils of the genus have been found in the Sarmiento, Casamayor, Andesitas Huancache and Koluel Kaike Formations.

'', there was a noticeable diastema between the anterior teeth and the premolars. In ''Otrhonia'' this diastema was more elongated than in other genera, and the crown of the molars was higher (hypsodont). The first pair of upper incisors were quite large and directed downwards.

Classification

''Otrhonia muehlbergi'' was first described in 1901 by

Santiago Roth Santiago Roth (14 June 1850 – 4 August 1924) was a Swiss Argentine paleontologist and academic known for his fossil collections and Patagonian expeditions. Life Kaspar Jakob (Spanish: Santiago) was born and raised in Herisau, Canton Appenzel ...

, based on a fossil found 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 ...

near the

Lago Musters __NOTOC__ Lago, which means "lake" in Italian, Portuguese, Spanish and Galician, may refer to: Places *Lago, Calabria, a ''comune'' in the Province of Cosenza, Italy *Lago, Mexico, a municipality zone in the State of Mexico *Lago District, a ''dis ...

(hence its name, derived from the lake local name, Otròn), in terrains dating from the Eocene. ''Otrhonia'' was a notostylopid, a group of notoungulates with a curious mixture of basal and derived characteristics. ''Otrhonia'' may have been one of the more specialized forms of the family, and is also one of the latest known forms from it.

Paleoecology

''Otrhonia'' was a terrestrial animal, feeding on leaves and fruits. There isn't any animal from modern South America sharing the same dentition, but it is vaguely similar to that of the Australian

koala The koala or, inaccurately, koala bear (''Phascolarctos cinereus''), is an arboreal herbivorous marsupial native to Australia. It is the only extant representative of the family Phascolarctidae and its closest living relatives are the w ...

, an arboreal animal.

Bibliography

*G. G. Simpson. 1948. The beginning of the age of mammals in South America. Part I. Bulletin of the American Museum of Natural History 91:1-232 *G. G. Simpson. 1967. The Ameghinos' localities for early Cenozoic mammals in Patagonia. Bulletin of the Museum of Comparative Zoology 136:63-76 *Darin A. Croft, Illustrated by Velizar Simeonovski. 2016. Horned Armadillos and Rafting Monkeys-TheFascinating Fossil Mammals of South America {{Taxonbar, from=Q60978321 Notoungulates Eocene mammals of South America Paleogene Argentina Fossils of Argentina Fossil taxa described in 1901 Prehistoric placental genera