As part of the project Programa Regional de Biodiversidad, subprograma Linea Base de Conoci- miento de la Biodiversidad del Choco , designed to document the mammalian fauna of the Biogeographic Choco, museum voucher specimens from the Colombian Chocoan Region deposited in American institutions have been taxonomically assessed in the past three years. Herein, we review the morphological variation, distribution patterns, and taxonomy of night monkeys in the genus Aotus from northwestern Colombia deposited at the Field Museum of Natural History (FMNH), and GIS based analyses and Maxent modeling are used to define the geographic extent and ecological limiting factors of the analyzed taxa. Our Principal Component Analysis showed high variation in skull morphology among Aotus from northwestern Colombia. However, differences observed in both discrete and morphometric analyses of the interorbital region of A. zonalis (more depressed than that in the grographically adjacent A. griseimembra and A. lemurinus ) appear as good diagnostic characters for this taxon. Our analyses on the ecological variation associated with collecting localities of Aotus specimens support the geographic subdivision previously proposed based on karyotypic data. Based on obtained models of potential distribution we define the location and extent of potential contact zones among species of Aotus from northwestern Colombia.