Froehlich et al. (1991) conducted the first explicitly phylogenetic analysis of the spider monkeys using 50 cranial and dental characters scored for seven putative taxa of Ateles. They concluded that the genus could be divided into three clades, merging some of the taxa previously recognized as distinct by Kellogg and Goldman (1944): Clade 1 consisted of Kellogg and Goldman’s (1944) A. p.paniscus; Clade 2 comprised A. hybridus – which Kellogg and Goldman (1944) had included as a subspecies within Ateles belzebuth – as well as the Mesoamerican and Pacific coast forms(A. geoffroyi, A. fusciceps = A. fusciceps fusciceps, and A. robustus = A.fusciceps rufiventris); and Clade 3 consisted of the all the northwestern,southwestern, central, and southeastern Amazonian forms, which correspond to contemporary A. belzebuth plus Kellogg and Goldman’s (1944) A. p. chamek and A. b. marginatus (Table 1). Froehlich et al. (1991) also suggested that all the South American forms comprise an interbreeding ring species, as they
found a morphological cline ranging from the Guianas to Venezuela (Froehlich et al., 1991).