Investigating Pterion from Two Perspectives: Phylogenetics and Biomechanics

Pterion is a skull landmark located directly behind the orbits where four cranial bones (sphenoid, parietal, temporal and frontal) articulate in 4 basic configurations: spheno-parietal, fronto-temporal, stellate and epipteric. Two hypotheses may explain the configurations and other aspects of pterion: 1) phylogenetic history reflected in conservative development in species with shared ancestry and 2) biomechanical forces due to chewing stressors on skull shape. Impacts of phylogenetics and biomechanics may be highlighted through the diversity of skull used. Skulls from UW's Burke Museum were assessed for pterion pattern, suture length and masseter and temporalis muscles in: Canis latrans (30), Vulpes vulpes (30), Ursus americanus, (30), Puma concolor (18), Lynx rufus (30), Papio hamadryas (8), Saimiri sciureus (8), Odocoileus hemionus (14), Cervus elaphus (4), Lepus americanus (21). Chi-square tests were used to test for an association of pterion pattern x Order, Family and Genus (Phylogenetics). Chi-squares are used to test for an association between pterion pattern and suture complexity (Biomechanics). Linear regressions are used to identify biomechanical predictors on cranial suture length. The results of the analysis provide evidence to support pterion is conservative at each phylogenetic level and that biomechanical variables do predict some of the variation in cranial suture length. This analysis is one of a handful to move beyond the traditional comparative approach and highlights the importance of phylogenetic relatedness and biomechanics influences on pterion.