Size and shape differences of the basicranium using craniometric morphometric methods

Abstract

This study predominantly examined sexually dimorphic size and shape differences of the basicranium. Landmark coordinate data was collected from crania from the Southeast Texas Applied Forensic Science Facility at Sam Houston State University in Huntsville, Texas. 42 landmarks from 191 individuals of reported White group affiliation were recorded, divided into data subsets, and used to compute traditional linear measurements, centroid sizes, and shape differences using principal components and relative warp graphs. Discriminant functions applied to all linear measurements and basicranial linear measurement produced classification accuracies of 88.48% and 71.73% respectively. T-tests of centroid sizes showed significant differences between male and female means for all subsets meaning that males exhibited significantly larger crania than females. Principal component analyses and their respective relative warp graphs exhibited relative homogeneity between male and female shapes within the sample. Despite the homogeneity of shape between the sexes, consistent significant shape differences between males and females were observed in the basicranium. Males consistently exhibited increased basicranial flexion between the landmarks Basion and Hormion in comparison to females. Increased basicranial flexion and larger cranial vaults in males compared to females supports previous allometric research stating that larger cranial vaults correlate with an increase in basicranial flexion. It is suggested that further research on the possible correlation of cranial vault size and basicranial flexion focuses on allometric differences rather than sexual dimorphism.