For this study, we used mitochondrial DNA (mtDNA) sequences to infer the relationships among the different taxa of spider mon- keys we sampled. Mitochondrial DNA has been suggested as an ideal marker to conduct studies of species and subspecies relation- ships as this marker (1) displays extensive intraspecific polymor- phism, (2) typically evolves faster than nuclear DNA, and (3) is present at higher copy number and thus is more readily extracted and amplified from a variety of sample types (feces, hair) than is nuclear DNA (Avise, 2000).