Incamys

Incamys is an extinct genus of chinchillid rodent that lived during the Late Oligocene (Deseadan) in what is now South America. Fossils of this genus have been found in the Salla Formation of Bolivia and the Agua de la Piedra^[1] and Sarmiento Formations of Argentina.^[2] Research on endocasts suggest they were group living using call communication like modern chinchillas.^[3]

Incamys Temporal range: Late Oligocene (Deseadan) ~28.0–24.0 Ma PreꞒ Ꞓ O S D C P T J K Pg N ↓
Scientific classification
Domain:	Eukaryota
Kingdom:	Animalia
Phylum:	Chordata
Class:	Mammalia
Order:	Rodentia
Family:	Chinchillidae
Genus:	†Incamys Hoffstetter and Lavocat 1970
Type species
†Incamys bolivianus Hoffstetter & Lavocat 1970
Species
I. bolivianus Hoffstetter & Lavocat 1970 I. menniorum Vucetich et al. 2015
Synonyms
I. pretiosus Lavocat 1976

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,^[4] 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, Argentina.^[5]

The following cladogram of the Caviomorpha is based on Busker et al. 2020, showing the position of Incamys.^[6]

Baluchimyinae Bugtimys zafarullahi "Phiomorpha" Phiomys andrewsi Metaphiomys schaubi Octodontoidea Prospaniomys priscus Myocastor coypus Echimyidae Proechimys polioplus Eumysops laeviplicatus Kannabaetomys amblyonyx Echimys chrysurus Ctenomyidae Ctenomys australis Plataeomys brevis Pithanotomys columnaris Octomys mimax Octodontomys gliroides Chasichimys bonaerense Chasicomys octodontiforme Acarechimys leucotheae Acarechimys minutus Acaremyidae Acaremys murinus Galileomys antelucanus Galileomys baios Erethizontoidea Steiromys detentus Eosteiromys homogenidens Dasyproctidae Dasyprocta azarae Node A Eoviscaccia frassinettii Eoviscaccia boliviana Garridomys curunuquem Incamys bolivianus Asteromys bolivianus Asteromys punctus Cephalomyidae Cephalomys ceciae Cephalomyopsis hypselodontus Litodontomys chubutensis Cephalomys arcidens Scotamys antiquus Neoepiblemidae Perimys intermedius Chinchillidae Lagostomus maximus Lagidium viscacia Chinchilla chinchilla Node B Banderomys leanzai Soriamys ganganensis Soriamys gaimanensis Luantus propheticus Guiomys unica Microcavia australis Cavia aperea Galea musteloides Dolichotis patagonum

Brain Endocast Research

Research on 30 million year old Incamys bolivianus virtual endocasts show they had expanded temporal lobes 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.^[3]

References

1. Candela, Adriana M.; Pérez, M. Encarnación; Rasia, Luciano L.; Cerdeño, Esperanza (2021-03-04). "New late Oligocene caviomorph rodents from Mendoza Province, central-western Argentina". Journal of Vertebrate Paleontology. 41 (2): e1929264. Bibcode:2021JVPal..41E9264C. doi:10.1080/02724634.2021.1929264. ISSN 0272-4634.
2. Patterson, B.; Wood, Albert Elmer (1982). "Rodents from the Deseadan Oligocene of Bolivia and the relationships of the caviomorpha". Bulletin of the Museum of Comparative Zoology. 149: 371–543. ISSN 0027-4100.
3. Bertrand, Ornella C.; Lang, Madlen M.; Ferreira, José D.; Kerber, Leonardo; Kynigopoulou, Zoi; Silcox, Mary T. (2024). "The virtual brain endocast of Incamys bolivianus : insight from the neurosensory system into the adaptive radiation of South American rodents". Papers in Palaeontology. 10 (3). Bibcode:2024PPal...10E1562B. doi:10.1002/spp2.1562. ISSN 2056-2799.
4. Lavocat, René (1976). "Rongeurs Caviomorphes de l'Oligocène de Bolivie. 2 Rongeurs du Bassin Deseadien de Salla-Luribat". Palaeovertebrata. 7: 15–90.
5. Vucetich, M.G.; Dozo, M.T.; Arnal, M.; Pérez, M.E. (2015-02-17). "New rodents (Mammalia) from the late Oligocene of Cabeza Blanca (Chubut) and the first rodent radiation in Patagonia". Historical Biology. 27 (2): 236–257. Bibcode:2015HBio...27..236V. doi:10.1080/08912963.2014.883506. hdl:11336/17958. ISSN 0891-2963.
6. Busker, Felipe; Dozo, María Teresa; Soto, Ignacio María (2020-10-01). "New remains of Cephalomys arcidens (Rodentia, Caviomorpha) and a redefinition of the enigmatic Cephalomyidae". Journal of Systematic Palaeontology. 18 (19): 1589–1629. Bibcode:2020JSPal..18.1589B. doi:10.1080/14772019.2020.1796833. ISSN 1477-2019.