The 82nd Annual Meeting of the American Association of Physical Anthropologists (2013)


New interpretations of the positional behaviors of the Dominican subfossil, Antillothrix bernensis, from the pectoral and pelvic girdles

JUSTIN T. GLADMAN1,2 and ALFRED L. ROSENBERGER1,2,3.

1Department of Anthropology, The Graduate Center, City University of New York, 2New York Consortium in Evolutionary Primatology, NYCEP, 3Department of Anthropology and Archaeology, Brooklyn College, City University of New York

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Subfossil platyrrhine postcranial remains from the Dominican Republic include a partial sacrum, several os coxae, and the first scapulae from the Caribbean. These remains, attributed to Antillothrix bernensis, exhibit a unique mosaic of morphology not found in modern platyrrhines, potentially expanding the diversity of platyrrhine positional behaviors and adding to the novel behaviors interpreted for other Caribbean fossil taxa (i.e., Xenothrix and Paralouatta). Based on absolute size and published mass regressions, Antillothrix was larger than a male Cebus, but smaller than most atelids (~3.5-6kg). Although the new specimen may approach the size range dominated by prehensile-tailed platyrrhines, the fragmentary sacrum does not appear to indicate such adaptations based on its low sacral canal height index (<0.80). The os coxae have expanded iliac and deeply excavated gluteal planes, a morphology found in atelids that might indicate powerful hindlimb-assisted climbing or anti-pronograde behaviors. However, the ratio of the ventral to dorsal acetabulum walls (<0.65) is unlike the roughly equal walls in atelids, possibly indicating more pronograde positional behaviors for Antillothrix. The blade of the scapula strongly resembles quadrupedal primates, with its greater length across the spine than between the superior and inferior angles. The morphology of the shoulder joint, especially in the robust acromion and short coracoid with an expanded attachment for the coracoclavicular ligament, is unlike any modern platyrrhine and shares similarities with slow-climbing lorises. Behaviorally, these new fossils are best reconstructed as of a moderately large platyrrhine practicing arboreal quadrupedalism, possibly with specialized climbing adaptations not found amongst modern platyrrhines.

This work was supported by the New York Consortium in Evolutionary Primatology, NSF DGE 0966166 (IGERT).

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