Why Owl Monkeys Are Pitheciids: Morphology, Adaptations, and the Evolutionary History of the Aotus Lineage

Abstract

Phylogeny reconstruction is an estimation of genealogical history, not an exact rendering of it, and no method of phylogeny reconstruction is infallible. The cladistic relationships of the owl monkey, Aotus, are the most hotly contested node of New World monkey interrelationships. The alternative hypotheses can be described taxonomically: Aotus is monophyletically related to either cebids or pitheciids. As predictive propositions, each notion should be evaluated by its explanatory power. The cebid hypothesis predicts that Aotus broadly shares adaptations in morphology, behavior, and ecology with cebines and/or callitrichines, while the pitheciid hypothesis predicts extensive overlap with Callicebus and/or pitheciins. We find no support for the cebid hypothesis and commanding support for the pitheciid hypothesis in the form of integrated morphological and behavioral complexes that are likely to be homologously derived. More attention should be directed toward understanding why the morphology and molecules do not align, from both biological and methodological perspectives.