''Colpodon'' 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 herbivorous

mammal Mammals () are a group of vertebrate animals constituting the class Mammalia (), characterized by the presence of mammary glands which in females produce milk for feeding (nursing) their young, a neocortex (a region of the brain), fur or ...

, belonging to the order Notoungulata. It lived during 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 today

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

Chile Chile, officially the Republic of Chile, is a country in the western part of South America. It is the southernmost country in the world, and the closest to Antarctica, occupying a long and narrow strip of land between the Andes to the east a ...

, 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 southe ...

Description

This animal is almost exclusively known from cranial remains, and its general appearance is globally unknown. From a comparison with some of its better known relatives, like ''

Scarrittia ''Scarrittia'' is an extinct genus of hoofed mammal of the family Leontiniidae, native to South America during the Oligocene, Late Oligocene epoch (Deseadan in the South American land mammal age, SALMA classification). Description ''Scarritt ...

'' and ''

Huilatherium ''Huilatherium'' is an extinct genus of leontiniid, a group of hoofed mammals belonging to the order Notoungulata, that comprises other South American ungulate families that evolved in parallel with some mammals of the Northern hemisphere. The l ...

'', it can be supposed that ''Colpodon'' was a relatively heavy-shaped animal, with a stature comparable to that of a

sheep Sheep or domestic sheep (''Ovis aries'') are domesticated, ruminant mammals typically kept as livestock. Although the term ''sheep'' can apply to other species in the genus ''Ovis'', in everyday usage it almost always refers to domesticated s ...

. Its skull was rather short and tall, with a characteristic set of teeth, differing from most of its close relatives, the

Leontiniidae Leontiniidae is an extinct family comprising eighteen genera of notoungulate mammals known from the Middle Eocene (Mustersan) to Late Miocene (Huayquerian) of South America South America is a continent entirely in the Western Hemisphe ...

. The upper canines were completely absent, and the incisors were well-developed bu lacking labial girdles.

Classification

''Colpodon'' was one of the first notoungulates ever discovered. It was first described in 1885 by Hermann Burmeister, who described the genus based on two upper and two lower molars found near the mouth of the Chubut River in

. Burmeister considered ''Colpodon'' as an intermediate form between ''

Nesodon ''Nesodon'' ("island tooth")Palmer (1904) p. 457. is a genus of Miocene mammal belonging to the extinct order Notoungulata which inhabited southern South America during the Late Oligocene to Miocene living from 29.0 to 16.3 Ma and existed fo ...

'' and '' Homalodotherium''. Subsequently, Burmeister described another species of ''Colpodon'', ''C. propinquus''. In the early 1900s,

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 ...

described other species of ''Colpodon'', ''C. distinctus'' and ''C. plicatus'', and believed that this animal was a member of the family Leontiniidae. In the following years ''Colpodon'' was variously placed among Leontiniidae and

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 ...

due to its peculiar dentition with characters shared by both families ; ''Colpodon'' also had a symmetrical astragalus, like the Notohippidae. In 2012 another species of ''Colpodon'', ''C. antucoensis'', was described from

. This species is slightly more recent than the type species, and is differentiated from it by some dental characters and a narrower muzzle. Moreover, other fossil remains assigned to this genus have been found in the

Chichinales Formation The Chichinales Formation is a geological formation in Río Negro Province, Argentina which dates from the Late Oligocene to the Early Miocene, around 23 to 17.5 million years ago. It predominantly consists of pyroclastic deposits, which were depo ...

of Río Negro Province in Argentina. ''Colpodon'' is currently considered a derived member of the family Leontiniidae, a group of heavy-built notoungulates common during the

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 ...

. The 2012 study showed a close relationship between ''Colpodon'', ''

'' and ''

Taubatherium ''Taubatherium'' is an extinct genus of mammal, belonging to the order Notoungulata. It lived during the Late Oligocene, in what is today Brazil, in South America. Description Fossils of this animal indicates that it had a fairly robust build, ...

'', two leontiniids from a tropical clade whose remains have been found in

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 ...

and

Brazil Brazil ( pt, Brasil; ), officially the Federative Republic of Brazil (Portuguese: ), is the largest country in both South America and Latin America. At and with over 217 million people, Brazil is the world's fifth-largest country by area ...

References

*G. Burmeister. 1885. Examen critico de los mamiferos y reptiles fosiles denominados por D. Augusto Bravard y mencionados en su obra precedente. Annales del Museo Nacional de Buenos Aires 3:93-174 *F. Ameghino. 1904. Nuevas especies de mamíferos, cretáceos y terciarios de la República Argentina ew species of mammals, Cretaceous and Tertiarty, from the Argentine Republic Anales de la Sociedad Cientifica Argentina 56–58:1-142 {{Taxonbar, from=Q21078346 Toxodonts Miocene mammals of South America Neogene Argentina Fossils of Argentina Fossil taxa described in 1895 Taxa named by Florentino Ameghino Prehistoric placental genera Golfo San Jorge Basin Chichinales Formation Sarmiento Formation