Syntopy of cryptic <italic>Phyllomys</italic> (Rodentia: Echimyidae) species: description of the karyotype of <italic>Phyllomys nigrispinus</italic> and an expansion of the geographic distribution of <italic>Phyllomys sulinus</italic>.

The echimyid rodents of the genus <italic>Phyllomys</italic> are medium-sized arboreal spiny rats endemic to the Atlantic Forest of Brazil. The genus is currently composed of 13 species, although there are at least four other undescribed species. The ecology, zoogeography and diversity of the genus are still poorly understood. Here, we provide the first record of <italic>Phyllomys sulinus</italic> from the Brazilian state of Rio de Janeiro, based on a specimen collected in the Serra da Bocaina National Park, which extends the known geographic range of the species approximately 130 km to the northeast. At this site, <italic>P. sulinus</italic> occurred in syntopy with the cryptic <italic>Phyllomys nigrispinus</italic>. We describe the karyotype of <italic>P. nigrispinus</italic> for the first time and identify two different diploid numbers (2n=84 and 85). We also conducted a molecular analysis of the cytochrome <italic>b</italic> gene of five specimens, which we identified by phylogenetic reconstruction. Our findings reinforce the importance of molecular data, such as DNA sequences, and karyotypes for the differentiation of cryptic, syntopic species. [ABSTRACT FROM AUTHOR]