Reconstructing dietary ecology of extinct strepsirrhines (Primates, Mammalia) with new approaches for characterizing and analyzing tooth shape

The morphological and ecological diversity of lemurs and lorisiformes once
rivalled the rest of the primate order. Here, we assemble a dataset of 3D
models representing the second mandibular molars of a wide range of extant
and fossil strepsirrhines encompassing this diversity. We use these models
to distill quantitative descriptors of tooth form and then analyze these
data using new analytical methods. We employ a recently developed dental
topography metric (ariaDNE), which is less sensitive to details of random
error in 3D model quality than previously used metrics (e.g., DNE);
Bayesian multinomial modelling with metrics designed to measure
overfitting risk; and a tooth segmentation algorithm that allows the
shapes of disaggregated tooth surface features to be quantified using
dental topography metrics. This approach is successful at reclassifying
extant strepsirrhine primates to known dietary ecology and indicates that
the averaging of morphological information across the tooth surface does
not interfere with the ability of dental topography metrics to predict
dietary adaptation. When applied to extinct species, many subfossil lemurs
and the most basal fossil strepsirrhines are predicted to have been
primarily frugivorous or gummivorous. This supports an ecological
contraction among the extant lemurs and the importance of frugivory in the
origins of crown Strepsirrhini, potentially to avoid competition with more
insectivorous and folivorous members of Paleogene Afro-Arabian primate
faunas.