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

Opisthocranion migration: female progenesis in the vervet (Chlorocebus aethiops) cranium


Anthropology, New Mexico State University

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Several investigations into intraspecific differences in patterns of growth and development of the vervet monkey (Chlorocebus aethiops) have found progenesis (early growth cessation) in females, but the effect of this developmental difference on the cranium has not been investigated. This study seeks to correct this deficiency by examining skeletons of 36 individuals from a single, wild population from Kibwezi, Kenya. The sample is comprised of both males (n=17) and females (n=19) that range in age from infant to adult. The specimens were placed into discrete age classes using previously established dental eruption patterns. These classes were then plotted against the distance from opisthocranion to lambda suture.

The distance from opisthocranion to lambda suture was found to shrink throughout ontogeny in both sexes, but remains relatively large in adult females who are therefore, with regard to this feature, paedomorphic when compared with adult males. For juveniles without fully erupted canines and no M3, the average distance for males (n=9) is 10.5 mm and for females (n=4) is 10.6 mm. In contrast, a statistically significant difference (p=0.00016) was found between the adult male distance (n=4, average=3.95 mm) and the adult female distance (n=10, average=8.47 mm). This cranial variable, here entitled ‘opisthocranion migration,’ illustrates that the developmental process of progenesis in female vervet monkeys is evinced in the morphology of the skull. Due to the consistent sexual dimorphism of this feature, it is also possible to use the degree of opisthocranion migration in adults as a tool for sex estimation in this species.

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