Gracilinanus microtarsus, from the Atlantic Forest and G. agilis, widespread in central Brazil in the Cerrado and in the northeastern Caatinga are two small Neotropical arboreal opossum species not frequently recorded in simpatry. Here we report eight G. agilis specimens from three localities and 17 G. microtarsus, from 10 localities, all in Minas Gerais, Rio de Janeiro and Bahia states. Species proper identification followed diagnostic characters as appearance of dorsum pelage, ocular-mark, ears and tail lengths and size proportion of the posteromedial vacuities in cranium. Chromosomes in metaphases of five specimens were obtained for both species. Our records extend the previous known geographical distribution of G. microtarsus to Chapada Diamantina, in Bahia State and report the occurrence of both species in simpatry. G. microtarsus, in coastal area, was captured in dense ombrophilous and in semideciduous forests, in deciduous seasonal forest and Cerradão in Chapada Diamantina. G. agilis was recorded in gallery forests of Cerrado and very green and dense bush formation of Caatinga. Autosomal complement showed the same diploid and autosomal number already described for both species (2n = 14, NA = 24). Measurements are according to those given in literature and pelage characteristics were useful for the correct species identification. Here we report both G. agilis, described to be endemic to the Cerrado/Caatinga, in opposite to G. microtarsus, considered to be endemic to Atlantic Forest occurring in simpatry in two localities of the Cerrado. Such results indicates that long term trapping effort are necessary to a better definition of species taxonomy, distribution patterns along time and comprehensive understanding how anthropic environmental changes can be interfering in their evolutionary history.
South America; neotropical marsupials; karyotypes; habitat use
