''Incamys'' is an extinct

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 ...

of chinchillid

rodent Rodents (from Latin , 'to gnaw') are mammals of the Order (biology), order Rodentia ( ), which are characterized by a single pair of continuously growing incisors in each of the upper and Mandible, lower jaws. About 40% of all mammal specie ...

that lived during the

Late Oligocene The Chattian is, in the geologic timescale The geologic time scale or geological time scale (GTS) is a representation of time based on the rock record of Earth. It is a system of chronological dating that uses chronostratigraphy (the pro ...

(

Deseadan The Deseadan () 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 follows the Tingu ...

) in what is now

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 ...

. Fossils of this genus have been found in the Salla Formation of

Bolivia Bolivia, officially the Plurinational State of Bolivia, is a landlocked country located in central South America. The country features diverse geography, including vast Amazonian plains, tropical lowlands, mountains, the Gran Chaco Province, w ...

and the Agua de la Piedra and

Sarmiento Formation The Sarmiento Formation (Spanish language, 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 y ...

s of

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 ...

. Research on endocasts suggest they were group living using call communication like modern chinchillas.

Taxonomy

''Incamys'' was first described by Hoffstetter and Lavocat, based on remains found in the Salla Formation of Bolivia, with the proposed type species being ''Incamys bolivianus'', referring to the country it was found in. Later, in 1976, a new species was named, ''I. pretiosus'', which was subsequently found to be a junior synonym of the type species. In 2015, Vucetich and colleagues described a new species of ''Incamys'', ''I. menniorum'', from the Sarmiento Formation of

Chubut Province Chubut ( from Tehuelche language, Tehuelche 'transparent'; ) is a provinces of Argentina, province in southern Argentina, situated between the 42nd parallel south (the border with Río Negro Province), the 46th parallel south (bordering Santa ...

, Argentina. The following cladogram of the

Caviomorpha Caviomorpha is the rodent parvorder that unites all New World hystricognaths. It is supported by both fossil and molecular evidence. The Caviomorpha was for a time considered to be a separate order outside the Rodentia, but is now accepted as ...

is based on Busker ''et al.'' 2020, showing the position of ''Incamys''.

Brain endocasts

Research on 30 million-year-old ''Incamys bolivianus'' virtual endocasts show they had expanded

temporal lobe The temporal lobe is one of the four major lobes of the cerebral cortex in the brain of mammals. The temporal lobe is located beneath the lateral fissure on both cerebral hemispheres of the mammalian brain. The temporal lobe is involved in pr ...

s in the cerebrum and large caudal colliculi in the midbrain, arguing they had enhanced auditory acuity and vocalization. This is consistent with them living in social groups and using calls to communicate with each other, similar to modern chinchillas.

References

{{Taxonbar, from=Q114351124 Chinchillidae Oligocene rodents Oligocene mammals of South America Deseadan Paleogene Argentina Fossils of Argentina Paleogene Bolivia Fossils of Bolivia Fossil taxa described in 1970 Prehistoric rodent genera Golfo San Jorge Basin Sarmiento Formation