The 81st Annual Meeting of the American Association of Physical Anthropologists (2012)

Trigonid talonid height and dental shearing in a sample of euprimates


Evolutionary Anthropology, Duke University

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With the loss of the paraconid among the euprimates, there has been a reorganization of the tooth crown resulting in an overall reduction of the trigonid and expansion of the talonid basin. This project explores the relationship between trigonid and talonid height, shearing and dietary categories across a broad sample of primates. Buccal shearing crests 1-4 length and protoconid and hypoconid height were measured on m1. Shearing quotient (SQ) was calculated as residuals from a frugivore-based regression line of the log summed length of shearing crests regressed against the length of m1. SQ was calculated for crests 1-4, and 1-2 (trigonid), 3-4 (talonid). Relative height indices (RHI) were calculated as (hypoconid height * 100) / protoconid height.

RHI can distinguish primates of different dietary category with frugivores having the broadest range of RHI values, This perhaps indicates a release of selective constraints on this trait in frugivores. The partially insectivorous, Saimiri can also be distinguished from other genera based on RHI. When RHI was compared to SQ 1-2, 3-4, no significant relationship was found. All measures of SQ were able to distinguish frugivores, folivores, and insectivores suggesting that SQ measures calculated from a small sample of crests are still a useful measure for determining dietary category in incomplete fossil specimens. Interestingly, SQ 3-4 was better able to distinguish different species from each other than SQ 1-2 perhaps indicating a stronger phylogenetic component to shear crest length in the talonid than the trigonid.

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