''Argyrohyrax'' 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 of interatheriid notoungulate that lived during 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 ...

, of what is now Argentina and

Bolivia , image_flag = Bandera de Bolivia (Estado).svg , flag_alt = Horizontal tricolor (red, yellow, and green from top to bottom) with the coat of arms of Bolivia in the center , flag_alt2 = 7 × 7 square p ...

Description

This animal may have vaguely resembled a medium-sized ground-dwelling rodent, such as a marmot. Its skull was approximately 15 centimeters long, and its entire body may have reached one meter in length, including the tail. ''Argyrohyrax'' is differentiated from its closest relatives like '' Archaeophylus'' and ''

Cochilius ''Cochilius'' is an extinct genus of interatheriid notoungulate that lived between the Late Oligocene and the lower Miocene in what is now Argentina. Description The skull and skeleton show features also found in other similar contemporary o ...

'' by small differences in its dentition, notably the overlap of the first premolar base by parts of the canine and the second premolar. Its maxilla had a very prominent descending process, as in ''Cochilius''. The two first lower molars had a quadrangular trigonid and a subcircular talonid. The first lower premolar was canine-like. Compared to some of its later relatives, ''

Interatherium ''Interatherium'' is an extinct genus of interatheriid mammal from the Early to Middle Miocene (Colhuehuapian- Mayoan). Fossils have been found in the Santa Cruz, Collón Curá and Sarmiento Formations in Argentina.Fernández, M. (2015). Re ...

'' and ''

Protypotherium ''Protypotherium'' is an extinct genus of notoungulate mammals native to South America during the Oligocene and Miocene epochs. A number of closely related animals date back further, to the Eocene. Fossils of ''Protypotherium'' have been found in ...

'', ''Argyrohyrax'' had a moderately expanded zygomatic arch ; its radius had a slightly concave distal articular surface, and the articulation between its ulna and its humerus was less concave and more vertical.

Classification

''Argyrohyrax proavus'' was first described in 1897 by Florentino Ameghino ; he later described several other species, such as ''Argyrohyrax acuticostatus'', ''A. concentricus'', ''A. nesodontoides'', ''A. proavunculus'', currently considered identical to the type species. The genus ''Plagiarthrus'' is similarly considered synonymous with ''Argyrohyrax''.*B. Vera, E. Cerdeño, and M. Reguero. 2017. The Interatheriinae from the Late Oligocene of Mendoza (Argentina), with comments on some Deseadan Interatheriidae. Historical Biology 29(5):607-626 The genus ''Argyrohyrax'' is known from several fossilized remains discovered in Argentina, notably from the

Sarmiento Formation The Sarmiento Formation (Spanish: ''Formación Sarmiento''), in older literature described as the Casamayor Formation, is a geological formation in Chubut Province, Argentina, in central Patagonia, which spans around 30 million years from the mid- ...

in the provinces of Santa Cruz and

Chubut Chubut may refer to: * Chubut Province, Argentina * Chubut River in the Chubut Province * Chubut steamer duck The Chubut steamer duck or white-headed flightless steamer duck (''Tachyeres leucocephalus'') is a flightless duck endemic to Argenti ...

, from the

Agua de la Piedra Formation The Agua de la Piedra Formation (FAP, Spanish names include ''Estratos de Agua de la Piedra'' and ''Complejo Volcano-sedimentario del Terciario inferior'')Combina et al., 1994, p.418 is a Late Oligocene (Deseadan in the SALMA classification) geol ...

in Mendoza Province and from the

Fray Bentos Formation Fray or Frays or The Fray may refer to: Arts, entertainment, and media Fictional entities *Fray, a phenomenon in Terry Pratchett's ''The Carpet People'' *Fray, the main character in the video games: **''Fray in Magical Adventure'' **''Fray CD'' ...

in the Corrientes Province. ''Argyrohyrax'' belonged to the family

Interatheriidae Interatheriidae is an extinct family of notoungulate mammals from South America. Interatheriids are known from the Middle Eocene (Mustersan) to the Early Pliocene (Montehermosan).McKenna & Bell, 1997Linares, 2004 These animals were principally sm ...

, a group of medium-sized notoungulates, with a superficially rodent-like appearance. Several characteristics of its skull and dentition suggests that ''Argyrohyrax'' was nested as a basal member of the group.

References

*F. Ameghino. 1897. Mammiféres crétacés de l’Argentine (Deuxième contribution à la connaissance de la fauna mammalogique de couches à Pyrotherium) retaceous mammals of Argentina (second contribution to the knowledge of the mammalian fauna of the Pyrotherium Beds) Boletin Instituto Geografico Argentino 18(4–9):406-521 *F. Ameghino. 1901. Notices préliminaires sur des ongulés nouveaux des terrains crétacés de Patagonie reliminary notes on new ungulates from the Cretaceous terrains of Patagonia Boletin de la Academia Nacional de Ciencias de Córdoba 16:349-429 {{Taxonbar, from=Q110464385 Typotheres Oligocene mammals of South America Paleogene Argentina Fossils of Argentina Paleogene Bolivia Fossils of Bolivia Deseadan Taxa named by Florentino Ameghino Fossil taxa described in 1897 Prehistoric placental genera Golfo San Jorge Basin Paraná Basin Sarmiento Formation