Ecological divergence and medial cuneiform morphology in gorillas

Area of Science:

• Primate anatomy
• Functional morphology
• Evolutionary biology

Background:

• Gorillas, closely related primates, exhibit varied arboreal behaviors and diets.
• Medial cuneiform bone morphology may reflect functional differences in hallucial (big toe) abduction and arboreality.

Purpose of the Study:

• To test if medial cuneiform morphology in gorillas correlates with hallucial abduction ability and arboreality.
• To investigate functional differences between western and eastern gorilla taxa based on foot bone anatomy.

Main Methods:

• Utilized a three-dimensional methodology to measure key features of the medial cuneiform bone.
• Analyzed angles between articular surfaces, relative areas, and curvatures of the hallucial articular facet.

Main Results:

• Medial cuneiform morphology partially confirmed functional predictions, differentiating western gorillas from eastern gorillas.
• Western gorillas possess a more medially oriented, larger, and more curved hallucial facet, suggesting a more prehensile hallux.
• Differences between Grauer's and mountain gorillas were not clearly linked to hallucial abduction or arboreality.

Conclusions:

• Ecological divergence likely explains the distinct medial cuneiform morphology between western and eastern gorillas.
• Western gorillas show adaptations for a more prehensile hallux, while eastern gorillas appear adapted for a more stable, plantigrade foot posture.
• Further research is needed to understand non-adaptive differences within eastern gorilla taxa.