Paleobiology of Protopithecus brasiliensis, a Plus-Size Pleistocene Platyrrhine from Brazil

by Halenar, Lauren B., Ph.D., CITY UNIVERSITY OF NEW YORK, 2012, 253 pages; 3499243

Abstract:

This dissertation tested several hypotheses concerning the paleobiology of the extinct platyrrhine Protopithecus brasiliensis in order to fill in many of the gaps in our knowledge of this fossil and the evolutionary history of its ateline relatives. Both cranial and postcranial morphology were examined using three-dimensional geometric morphometric (3DGM) techniques to investigate the body size, basicranial shape, and locomotor repertoire of the fossil.

Regression equations based on platyrrhine postcranial dimensions support the hypothesis that Protopithecus belonged to a size class of platyrrhines that no longer survives, yielding an average estimate of 23 kg. This large body mass led to a previous suggestion that Protopithecus would have traveled on the ground, but detailed observations of the skeleton found no adaptations to terrestriality. Instead, the original hypothesis of a suspensory mode of locomotion was supported, particularly based on analyses of the elbow and phalanges. The femur and pelvis exhibit robust muscle markings, suggesting that Protopithecus, like Alouatta, also used hindlimb suspension and climbing.

A phylogenetic link between Protopithecus and Alouatta was originally proposed based on suggested synapomorphies of the cranial base and mandible, traditionally related to opening subbasal space for the howler's uniquely enlarged hyoid. These features were examined in more detail to test the hypothesis that Protopithecus also had an enlarged hyoid. Based on the landmark dataset analysed here, the Protopithecus cranial base and mandible were more similar to the generalized, potentially primitive, condition seen in Lagothrix . The occipital region, however, was similar to Alouatta in shape and orientation, a potential phylogenetic link but a neutral feature with respect to the question of hyoid enlargement. The large body size of Protopithecus needs to be considered here as well, since it is possible that at 23 kg the fossil had sufficient space in the throat to accommodate a relatively large hyoid without extreme cranial base modifications comparable to those of the much smaller Alouatta.

Protopithecus demonstrates derived alouattin, primitive ateline, and autapomorphic traits. Based on the fossil hip and thigh morphology, as well as the modified occipital region and small brain size, a provisional phylogenetic position as a basal alouattin is supported.

AdviserAlfred R. Rosenberger
SchoolCITY UNIVERSITY OF NEW YORK
Source TypeDissertation
SubjectsPhysical anthropology; Evolution & development; Paleontology
Publication Number3499243

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