New Palaeogene caviomorphs (Rodentia, Hystricognathi) from Santa Rosa, Peru: systematics, biochronology, biogeography and early evolutionary trends

ARNAL, M.; KRAMARZ, A.; VUCETICH, M.G.; FRAILEY, C.D.; CAMPBELL, K.

Papers in Palaeontology

PALAEONTOLOGICAL ASSOC

Lugar: Londres; Año: 2019

2056-2802

The origin andearly evolution of South American rodents are ongoing subjects of debate. Thecaviomorphs of the Peruvian localities of Santa Rosa and Contamana are theoldest South American rodents so far known. The Santa Rosa rodents are abundantand diverse, but dating was based on biostratigraphy (?Eocene), whereas in variousContamana sites radiometric dates, vertebrate biochronology, and palynostratigraphysuggest an age of 41.6?40.94 Ma (late middle Eocene). Previous faunal comparisonsbetween the localities identified few shared taxa. In this work, we studied newand previously described rodent fossils from Santa Rosa and analyzed their biochronologicaland biogeographic implications. As a result of the taxonomic study, we recognizefive new taxa and three genera species for Santa Rosa, four of them previously knownonly from the Eocene Contamana region. Thus, the Santa Rosa and the late middleEocene Contamana assemblages appear to be chronologically closer than previouslythought. An ?Eocene age for Santa Rosa is substantiated by other mammals reportedfrom Santa Rosa. With 11 named genera and 15 species, the Santa Rosa rodentsrepresent the most species-rich South American Palaeogene rodent assemblageknown. The Eocene radiation in the Neotropics that gave rise to this diversity wasnot associated with an immediate geographic dispersion to higher latitudes,perhaps because different biogeographic barriers or factors of competition couldhave delayed their dispersal. Evidence suggests that replacement, rather than apersistence of conservative long-lasting lineages, was the dominant processamong Palaeogene tropical caviomorphs rodents.