Abrawayaomys ruschii is considered as a rare species due the scarcity of samples in scientific collections and in published lists, being difficult to assign it to any proposed suprageneric classification among the Sigmodontinae. We report here a new record of A. ruschii, the first for this species in the Rio de Janeiro state (Aldeia Sapucai - Terra Indígena do Bracuí, Angra dos Reis). Because of the small sample size it is not possible to define a precise geographic range, but the known localities in Brazil are in different ecoregions of the Atlantic forest. The present specimen was captured in a secondary forest habitat, near a mature forest. The karyotype revealed a diploid number of 58 chromosomes, with 25 pairs of acrocentric chromosomes, and four biarmed (metacentric and submetacentric) pairs of chromosomes.
Abrawayaomys; Atlantic Forest; rare species; new register; morphology and karyotype
