Most significantly,
when Ateles marginatus from northeastern Brazil is included in our
analysis, we find that this species does not belong in the same
clade as A. belzebuth and A. chamek as previously suggested. Rather,
it is inferred to be the sister taxon to all other species of spider
monkeys. Moreover, several of our analyses place Ateles paniscus
in a rather derived position in the Ateles phylogeny, as a sister
taxon to a clade containing the trans-Andean forms (A. geoffroyi
in Mesoamerica and A. fusciceps from the Pacific coast of South
America). Most previous studies (and ours, too, when A. marginatus
is not included in our dataset: Fig. 3E and F) have instead proposed
A. paniscus to be basal within the Ateles radiation, although one
cytogenetic study has placed it in a similar derived position to that
which we reconstruct here (Medeiros et al., 1997)