Protopithecus, Paralouatta, and Alouatta: The making of a platyrrhine folivore

COOKE, S.; HALENAR, L.; ROSENBERGER, A.L.; TEJEDOR, M.F.; HARTWIG, W.

Philadelphia, USA

Congreso; 72th Annual Meeting of the American Association of Physical Anthropologists; 2007

American Association of Physical Anthropologists

Howler monkeys are the most folivorous platyrrhine primates, and they are also highly unusual in cranial morphology. Recent discoveries of large and plus-sized subfossil alouattin platyrrhines in Cuba and Brazil provide insight into the mosaic craniodental evolution of Alouatta features and adaptations. Both incisor and cheek tooth morphology of Protopithecus and Paralouatta indicate that ancestral alouattins were not dedicated folivores; rather, they were highly frugivorous. This is consistent with character analyses and evolutionary scenarios based on the more restricted sample of modern ateline genera. While Protopithecus is still somewhat primitive in this regard, craniofacial and basicranial anatomy of both subfossils is distinctly similar to living howlers in features relating to head posture and the enlarged hyolaryngeal apparatus, showing that the howler-like vocalizations and head carriage were already established in ancestral alouattins. There is also evidence of a relatively small brain size in Protopithecus and Paralouatta, resembling Alouatta, and more tenuous indications of phyletic size decrease, suggesting that de-encephalization, body size increase and folivory may not be coupled adaptively as a folivory syndrome in this tribe. Knowing that definitive leafeating alouattins more closely related to Alouatta were already present in the middle Miocene of Colombia, these taxa demonstrate that alouattins experienced an adaptive radiation. They had a diverse and complex prior evolutionary history that far exceeds projections based on living forms alone or the close linkage and dental correspondence of Stirtonia from La Venta and living Alouatta. They also underscore the unique “semifolivorous” ways that characterize the platyrrhines’ only leaf-eating icon.