Dissection of a specimen of the South American primate genus Aotus was performed, focusing on the morphology of the hyoid apparatus and surrounding musculature within the hyoid region (the ventral side of the throat). Data collected from this dissection, along with data from published descriptions of primate genera from both primate suborders Haplorhini and Strepsirhini, were analyzed using the computer software program PAUP (Phylogenetic Analysis Using Parsimony). This analysis generated four equally probable phylogenetic trees (cladograms) depicting possible phylogenetic relationships of Aotus to other primates. While the cladograms differ in minor detail, they all show that Aotus appears to be more closely related to the more apomorphic suborder Haplorhini than to the Strepsirhini, and that it is a relatively plesiomorphous member of the haplorhine group. This suggests that the ancestor of the New World monkeys arrived in South America at about the time when haplorhine primates were beginning to diverge in the rest of the world, about 28 million years ago.
Immel '97, Melissa S., "Phylogenetic Systematics of the Primate Genus Aotus Based on Hyoid Morphology" (1997). Honors Projects. Paper 14.