Form differences in the fetal craniofacial complex:  A three dimensional (3D), morphological comparison between fetal pigtailed macaques (Macaca nemestrina) and humans (Homo sapiens)

While the form of the fetal craniofacial complex has been well documented in humans and in pigtailed macaques in two dimensions, there are no investigations that directly compare the fetal craniofacial morphology of these two primates. The purpose of this research is to provide the first three dimensional comparison of fetal craniofacial morphology between M. nemestrina and H. sapiens.  Euclidean Distance Matrix Analysis (EDMA) is used to test the null hypothesis that the macaque and human fetal craniofacial complex have similar forms.

The populations consist of 18 pigtailed macaques fetuses  (9 male and 9 females; mean age of 21 weeks) and 15 human fetuses (8 males and 7 females; mean age of 29 weeks).   Birth for the pigtailed macaque is estimated at 24.3 gestational weeks, while 40 gestational weeks is the estimated gestation time for humans.  Chronologically, the macaque population has completed 86% of their gestation, while the human population has completed 72% of their gestation.
 
Three dimensional (3D) coordinates of 14 landmarks on the face and inferior neurocranium were collected from 3D-CT reconstructed images and 2D axial slices.  For the human specimens, 3D coordinates were digitized using REMEDI, while landmarks for the macaque specimens were digitized using VoxBlast.  EDMA was used to test each population for the presence of sexual dimorphism.  No sexual dimorphism was present, thus males and females were combined in each population.
 
Results from EDMA failed to support the null hypothesis.  There were significant differences in the overall form of the fetal craniofacial complex.  The inferior neurocranium and upper face is wider along mediolateral axes in the macaque skull, relative to the human skull.  The macaque middle cranial fossa is shorter along anteroposterior axes, and the midface is more prognathic in the macaque.  Finally, the entire cranial base in the macaque is shorter, relative to the human.
 
Supported for the macaque fetal collection was provided by NIH grants DE02918, RR00166, HD08633, HD10356, HL19187, NSF grant SBR9601027,  Mark Diamond Research Foundation at SUNY Buffalo, and Sigma Xi Foundation and NSF grant BNS9100684 provided support for the collection of the human fetuses.