Sagittal craniofacial growth in the fetal macaque monkey Macaca nemestrina

Abstract

In the third trimester of fetal life in Macaca nemestrina, the craniofacial dimensions in the sagittal plane showed no statistically significant sexual differences. In the human fetus, facial dimensions and the anterior cranial base grow isometrically with proportional constancy relative to overall fetal length. In this study a linear regression in which the Y-intercept differed significantly from zero was used as an indicator of allometry. For the pooled male-female M. nemestrina sample, the regression coefficient for each variable was statistically significant for the linear function Y = a + b (CRL). The 99 per cent confidence intervals for the Y-intercepts of the variables measuring anterior and posterior upper facial height and pterygoid process length included zero, suggesting the proportional constancy relative to fetal size of isometric growth. The confidence intervals of the anterior, posterior, and total cranial base length did not include zero, suggesting allometric growth. The difference in the anterior cranial base growth pattern between human fetuses and those of M. nemestrina probably reflects the greater activity of midsphenoidal synchondrosis in M. nemestrina.