The development of size dimorphism in the craniofacial complex during the third trimester of prenatal growth in pigtailed macaques (Macaca nemestrina)

Since the pigtailed macaque is a highly dimorphic species, it is not surprising that there are many studies which examine the postnatal development of sexual dimorphism in this species.   However, there are very few studies that explore the development of sexual dimorphism prenatally.   The purpose of this paper is to investigate the development of sexual dimorphism in the craniofacial complex during the third trimester of prenatal growth and development in M. nemestrina.

The data for this study were obtained from the Regional Primate Center at the University of Washington in Seattle.  A suite of measurements were used to compare growth between 56 males and 63 females between 107 and 170 gestational days.  These measurements include 14 cephalometrics, 11 anthropometrics and dental maturation scores of all developing deciduous crown. One- way t-tests were used to determine if there are significant differences in growth between males and females (p < .05). In addition, discriminant function analysis was performed on animals between the ages of 130 - 140 gestational days in order to determine which measurements contribute to the ontogeny of size dimorphism.

Results indicate that the pre-sphenoid and basi-sphenoid portion of the cranial base, palatal length, posterior midface height and midface depth, maxillary central and lateral incisor, maxillary second molar, mandibular central incisor and mandibular canine showed significant levels of size dimorphism.  Discriminant function analysis revealed the cephalometric measurements that contribute to sexual dimorphism are the anterior cranial base, pre-pheniod and basi-sphenoid portion of the cranial base, posterior facial height, and total facial height.  The anthropometrics that contribute to the development of sexual dimorphism are interorbital breadth, ear and nose height.  The dental crowns that contribute to the development of sexual dimorphism are the maxilary central incisor, maxillary canine, maxillary first molar, mandibular central and lateral incisor, and mandibular canine.

This research was made possible by NIH grants DE02918, HD08633, HD10356, HL19187 and RR00166.