Isothrix

Abstract: Isothrix sinnamariensis sp. nov. est un Echimyide arboricole, nocturne, connu et decrit a partir de deux specimens captures dans une foret tropicale haute de basse altitude de Guyane francaise. Il est morphologiquement et moleculairement (sequencage de l'ADN mitochondrial) tres proche de Isothrix pagurus present dans le bassin amazonien bresilien, mais il differe de I. pagurus par le nombre de chromosomes (2n = 28 versus 2n = 22) et par un ensemble de rearrangements chromosomiques complexes montrant qu'il existe un solide isolement genetique entre ces deux especes.

Abstract: The genus Callistomys belongs to the rodent family Echimyidae, subfamily Echimyinae, and its only living representative is Callistomys pictus, a rare and vulnerable endemic species of the state of Bahia, Brazil. Callistomys has been previously classified as Nelomys, Loncheres, Isothrix and Echimys. In this paper we present the karyotype of Callistomys pictus, including CBG and GTG-banding patterns and silver staining of the nucleolus organizer regions (Ag-NORs). Comments on Callistomys pictus morphological traits and a compilation of Echimyinae chromosomal data are also included. Our analyses revealed that Callistomys can be recognized both by its distintinctive morphology and by its karyotype.