Late Oligocene caviomorph rodents from Contamana, Peruvian Amazonia

Abstract

The Deseadan South American Land Mammal Age (late Early Oligocene -Late Oligocene) attests to a time of great diversification in the caviomorph rodent fossil record. Nevertheless, Deseadan rodent-bearing localities in Neotropical lowlands are few and poorly known. Here we describe the rodent assemblages from two Late Oligocene localities, near Contamana, Loreto, Peru. Seven taxa are new to science: Palaeosteiromys amazonensis gen. et sp. nov., Plesiosteiromys newelli gen. et sp. nov., Loretomys minutus gen. et sp. nov., Scleromys praecursor sp. nov, Ucayalimys crassidens gen. et sp. nov., Chambiramys sylvaticus gen. et sp. nov. and Chambiramys shipiborum gen. et sp. nov. These rodent faunas show that caviomorphs were relatively diverse in Peruvian Amazonia during the Late Oligocene, with the co-occurrence of at least three extant superfamilies: Erethizontoidea, Octodontoidea and Chinchilloidea. Additionally, they mark the earliest known

Late middle Eocene caviomorph rodents from Contamana, Peruvian Amazonia

“…To sum up, the Eocene localities of Contamana constitute a homogeneous set from a geographical, taxonomic, and environmental perspective, contrary to the Deseadan (CTA-32 and CTA-61; Boivin et al, 2017) and Neogene ones . The latter are characterized by distinct environmental/depositional conditions, leading to different taxonomic assemblages in terms of composition and diversity.…”

“…As some determinations have evolved since then, synonymies are specified. The terminology for rodent dentition (Figures 2, 3) follows the nomenclature of Boivin et al (2017) based on Wood and Wilson (1936), Fields (1957), Marivaux et al (2004Marivaux et al ( , 2017, and Antoine et al (2012). Lower case letters are used for the lower dentition (i.e., dp, for decidual premolar; p, for premolar; m, for molar) and upper case letters for the upper dentition (i.e., dP, for decidual premolar; P, for premolar; M, for molar).…”

Upper molar morphology, homologies and evolutionary patterns of chinchilloid rodents (Mammalia, Caviomorpha)

“…Boivin et al. ) and early Miocene of Argentina (e.g. Ameghino, , ; Kramarz, ; Cerdeño & Vucetich, ) and Chile (Flynn et al.…”

“…Ucayalimys crassidens Boivin et al. is a possible Chinchilloidea from the late Oligocene of Contamana, Perú (Boivin et al. ) with tetralophodont M2.…”

“… is a possible Chinchilloidea from the late Oligocene of Contamana, Perú (Boivin et al. ) with tetralophodont M2. The incertae sedis caviomorph Aenigmys diamantensis Vucetich et al.…”