Sexual dimorphism in the cranium and endocast of the eastern lowland gorillas (Gorilla beringei graueri).

J Hum Evol

Department of African Zoology, Royal Museum for Central Africa, Leuvensesteenweg 13, 3080 Tervuren, Belgium.

Published: November 2023

AI Article Synopsis

  • This study investigates the sexual dimorphism in cranial structures and brain characteristics of eastern lowland gorillas, focusing on both external crania and internal endocasts.
  • Using CT scans and advanced 3D morphometric techniques, researchers identified significant differences in size and shape between male and female gorillas.
  • Findings revealed that males have larger, more elongated features including the face and brain structures, whereas females exhibit rounder cranial formations and specific differences in the positioning of the cerebellum and olfactory bulb.

Article Abstract

Sexual dimorphism of the nervous system has been reported for a wide range of vertebrates. However, understanding of sexual dimorphism in primate cranial structures and soft tissues, and more particularly the brain, remains limited. In this study, we aimed to investigate the external and internal (i.e., endocast) cranial differences between male and female eastern lowland gorillas (Gorilla beringei graueri). We examined the differences in the size, shape, and disparity with the aim to compare how sexual dimorphism can impact these two structures distinctively, with a particular focus on the endocranium. To do so, we reconstructed gorilla external crania and endocasts from CT scans and used 3D geometric morphometric techniques combined with multivariate analyses to assess the cranial and endocranial differences between the sexes. Our results highlighted sexual dimorphism for the external cranium and endocast with regard to both size and shape. In particular, males display an elongated face accompanied by a pronounced sagittal crest and an elongated endocast along the rostroposterior axis, in contrast to females who are identified by a more rounded brain case and endocast. Males also show a significantly larger external cranium and endocast size than females. In addition, we described important differences for the posterior cranial fossae (i.e., the position of the cerebellum within the brain case) and olfactory bulb between the two sexes. Particularly, our results highlighted that, relatively to males, females have larger posterior cranial fossae, whereas males have been characterized by a larger and rostrally oriented olfactory bulb.

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Source
http://dx.doi.org/10.1016/j.jhevol.2023.103439DOI Listing

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