''Otrhonia'' is an

extinct Extinction is the termination of an organism by the death of its Endling, last member. A taxon may become Functional extinction, functionally extinct before the death of its last member if it loses the capacity to Reproduction, reproduce and ...

genus Genus (; : genera ) is a taxonomic rank above species and below family (taxonomy), family as used in the biological classification of extant taxon, living and fossil organisms as well as Virus classification#ICTV classification, viruses. In bino ...

notoungulate 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 re ...

, belonging to the

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

family. It lived during the Late

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

, 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 considerably smaller portion in the Northern Hemisphere. It can also be described as the southern Subregion#Americas, subregion o ...

Description

This animal was approximately the size of a modern

racoon The raccoon ( or , ''Procyon lotor''), sometimes called the North American, northern or common raccoon (also spelled racoon) to distinguish it from other species of raccoon, is a mammal native to North America. It is the largest of the proc ...

, 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 Appenzell ...

, based on a fossil found in

Argentina Argentina, officially the Argentine Republic, is a country in the southern half of South America. It covers an area of , making it the List of South American countries by area, second-largest country in South America after Brazil, the fourt ...

near the Lago Musters (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 is no animal from modern South America sharing the same dentition, but it is vaguely similar to that of the

Australia Australia, officially the Commonwealth of Australia, is a country comprising mainland Australia, the mainland of the Australia (continent), Australian continent, the island of Tasmania and list of islands of Australia, numerous smaller isl ...

koala The koala (''Phascolarctos cinereus''), sometimes inaccurately called the koala bear, is an arboreal herbivorous marsupial native to Australia. It is the only Extant taxon, extant representative of the Family (biology), family ''Phascolar ...

, 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