The first record of Calomys hummelincki (Rodentia: Sigmodontinae) from the Lavrados of northern Brazil

The South American genus Calomys exhibits a disjunct distribution with most species inhabiting grasslands, savannas, and forest edges from ca. latitude 8° S in the highlands of Peru and the Caatinga of Brazil to ca. latitude 16° S in central Bolivia, and from there south into Argentine Patagonia. Only a single species (Calomys hummelincki) occurs in open habitats in northern South America. We report the first known specimen of Calomys hummelincki for Brazil. The specimen is deposited in the mammal collection of Museu de Zoologia da Universidade de São Paulo, São Paulo. It is a young adult female with two embryos collected on 13 March 1989 by C. M. Carvalho at Fazenda Salvamento, Roraima state, during a herpetofaunal survey. The specimen shares qualitative and quantitative characters with specimens from Venezuela and Curaçao, but also differs substantially in others. The record presented herein extends the known range of the species about 630 km southeastward from the nearest previous record (in Venezuela, Estado Bolívar, Sipao). This new record was obtained in a locality representative of the savannas of the Rio Branco – Rupununi region that supports a poorly known, but distinctive mammalian fauna. This entire eco-region represents a piece of the biogeographic puzzle resulting from the climate-dependent vegetation shifts that dominated the Quaternary of South America. This new record highlights the need to investigate and protect the biodiversity of the Rio Branco-Rupununi savannas.