Data from: Late Oligocene caviomorph rodents from Contamana, Peruvian Amazonia

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 occurrences of Scleromys, of a small erethizontid closely related to
Microsteiromys and of an adelphomyine closely reminiscent of Ricardomys
(all taxa previously restricted to Miocene localities thus far). They also
document a form potentially related to Eosallamys (previously known from
around the Eocene–Oligocene transition at Santa Rosa in Peruvian
Amazonia). Finally, the geographical range of Adelphomyinae and of
Deseadomys is widely expanded to the lower latitudes of South America for
the Deseadan interval. The latter elements, in addition to the record of a
very primitive species of Scleromys, suggest the absence of
palaeogeographical and palaeoenvironmental barriers within the southern
cone of South America before the Oligocene–Miocene transition.