Proa et al PeerJ Raw Data.zip

The form
of the cranium can vary extensively among closely related species of papionins
(Cercopithecidae, Primates), a fact that is often related to their adaptive
differences to distinct diets. Yet, the form of the cranium can also vary
greatly between males and females of the same species, even though both sexes
tend to have the same diet. Here we use finite elements models and geometric morphometrics
to test for differences in cranial biomechanical performance that could be
attributed to differences in diet and feeding habits in male and female
specimens of Papio anubis and Theropithecus gelada, two extant
papionin species with known diets. It is
expected that adaptation to that same diet must have occurred in both
sexes, despite differences in form. Strain contour plots show that differences
can be seen between male and female of each species, but differences between
male and female T. gelada are much
larger than those between male and female P.
anubis for all bites. Nevertheless, larger differences in strain are seen
between species, rather than between male and female of the same species. An
analysis of deformations shows male and female of each species falling with
each other, and away from the other species. P. anubis male and female deform almost identically, with the
female deforming only slightly less than the male for all bites. Differences
between male and female T. gelada are
more marked, with the female deforming far less than the male particularly
during incisor bites; the trajectory followed, though, is the same, with
differences being mainly in magnitude of deformation. These results are an
indicator that diet might have had a major adaptive effect on papionin cranial
form, but they also indicate that papionin cranial form may be highly
constrained by other non-masticatory functions. Also, these results highlight
the difficulties in trying to interpret dietary ecology from modes and
magnitudes of cranial deformation, which, being difficult in extant species
with known diets and sexes, becomes extremely challenging when applied to
extinct species.