''Protheosodon'' is an

extinct Extinction is the termination of a kind of organism or of a group of kinds (taxon), usually a species. The moment of extinction is generally considered to be the death of the last individual of the species, although the capacity to breed and ...

genus Genus ( plural genera ) is a taxonomic rank used in the biological classification of extant taxon, living and fossil organisms as well as Virus classification#ICTV classification, viruses. In the hierarchy of biological classification, genus com ...

of proterotheriid

litoptern Litopterna (from grc, λῑτή πτέρνα "smooth heel") is an extinct order of fossil hoofed mammals from the Cenozoic era. The order is one of the five great orders of South American ungulates that were endemic to the continent, until th ...

. It lived from the Late

Oligocene The Oligocene ( ) is a geologic epoch of the Paleogene Period and extends from about 33.9 million to 23 million years before the present ( to ). As with other older geologic periods, the rock beds that define the epoch are well identified but the ...

to the Early

Miocene The Miocene ( ) is the first 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 means "less recen ...

in what is now

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 ...

and

Colombia Colombia (, ; ), officially the Republic of Colombia, is a country in South America with insular regions in North America—near Nicaragua's Caribbean coast—as well as in the Pacific Ocean. The Colombian mainland is bordered by the Car ...

Description

It was a medium-sized animal, smaller than the extant vicuña. The lower incisors, unlike those of more derived proterotheriids such as ''

Diadiaphorus ''Diadiaphorus'' is an extinct genus of litoptern mammal from the Miocene of Argentina ( Ituzaingó, Pinturas, Chiquimil and Santa Cruz Formations) and Bolivia ( Nazareno Formation), South America. Description ''Diadiaphorus'' closely rese ...

'', were relatively small and unspecialized. The lower dentition was complete and there was no trace of

diastema A diastema (plural diastemata, from Greek διάστημα, space) is a space or gap between two teeth. Many species of mammals have diastemata as a normal feature, most commonly between the incisors and molars. More colloquially, the condition ...

. The upper teeth were similar to those of ''

Anisolambda ''Anisolambda'' is an extinct genus of litoptern. It lived from the Late Paleocene to the Middle Eocene in what is now Argentina. Description This animal is mostly known from fossils of its maxilla, mandible and teeth, and it is therefore diff ...

'' and ''

Polymorphis ''Polymorphis'' is an extinct genus of litopterns belonging to the family Macraucheniidae. It lived during the Middle Eocene of Argentina. Taxonomy The type species of ''Polymorphis'' is ''Polymorphis lechei''. Both the genus and the species w ...

''. The mandible had a very high vertical branch. Its leg bones, firstly attributed to a notoungulate, are incompletely known.

Classification

The Deseado formation of Patagonia (1914) (14577238310)

''Protheosodon coniferus'' was first described in 1897 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 fossils found in

Deseadan The Deseadan ( es, Deseadense) age is a period of geologic time (29.0–21.0 Ma) within the Oligocene epoch of the Paleogene to the Early Miocene epoch of the Neogene, used more specifically within the SALMA classification of South America. It fo ...

deposits from

Chubut Province Chubut ( es, Provincia del Chubut, ; cy, Talaith Chubut) is a province in southern Argentina, situated between the 42nd parallel south (the border with Río Negro Province), the 46th parallel south (bordering Santa Cruz Province), the Andes ra ...

. Other fossils attributed to the genus have been found in slightly older deposits in

. ''Protheosodon'' was initially thought to be a member of Macraucheniidae, mainly based on characteristics from its lower teeth. Subsequent researches has indicated that it was more probably nested within

Proterotheriidae Proterotheriidae is an extinction, extinct family of fossil ungulates from the Cenozoic era that displays toe reduction. Despite resembling primitive, small horses, they were only distantly related to them, and instead belonged to the native Sou ...

, a group of litopterns which, in the course of their evolution, developed horse-like forms, well adapted for running. It may have been a member of

Anisolambdinae Proterotheriidae is an extinct family of fossil ungulates from the Cenozoic era that displays toe reduction. Despite resembling primitive, small horses, they were only distantly related to them, and instead belonged to the native South American ...

, the most basal subfamily of proterotheriids. ''Protheosodon'' seems to have been part of a collateral branch, contemporary to other, more derived, proterotheriids.

Bibliography

*F. Ameghino. 1897. Mamiferos Cretaceos de la Argentina. Segunda contribucion al conocimiento de la fauna mastologica de las capas con restos de Pyrotherium. Boletin Instituto Geografico Argentino 18:406-521 *F. B. Loomis. 1914. The Deseado Formation of Patagonia 1–232 {{Taxonbar, from=Q60977301 Proterotheriids Oligocene mammals of South America Miocene mammals of South America Paleogene Argentina Neogene Colombia Fossils of Argentina Fossils of Colombia Colhuehuapian Deseadan Fossil taxa described in 1897 Taxa named by Florentino Ameghino Prehistoric placental genera Golfo San Jorge Basin Sarmiento Formation