A preliminary survey of temporal lobe and cranial morphometrics in extant haplorrhines

Abstract

The temporal lobes of the brain, located in the middle cranial fossae, are sensitive to changes in the cranial base. The relationships between the temporal lobes and middle fossae are relevant in evaluating the constraints in functional craniology and allowing inferences in primate paleoneurology. Utilising imaging scans of four extant species from the Ceboidea and Cercopithecoidea (n=32), we examined ex-vivo crania using Computed Tomography (CT) and Magnetic Resonance Imaging (MRI) of the in-vivo brain to generate virtual models of the cranial base and brain. Linear metrics were used to approximate the dimensions of fossae shape and size before interspecific variation was assessed using Principal Component Analysis (PCA). Temporal lobe volume was calculated directly from the MRI and linear regression used to examine any correlation with the middle cranial fossae. Results indicated that size was the only factor involved in the morphological variation of the fossa, with no recognisable shape differences between species. Temporal lobe volume showed a strong correlation with all linear metrics. Future research should incorporate larger samples with interspecific and intraspecific variation investigated to elucidate the biological and evolutionary implications for primate functional craniology and paleoneurology.