Only skull-deep? Headbutting adaptations may not extend to the brain cavity

Area of Science:

• Paleontology
• Zoology
• Comparative Anatomy

Background:

• Muskoxen (Ovibos moschatus) exhibit high-impact headbutting behavior.
• The anatomical adaptations protecting their brains are largely uninvestigated.
• Digitiform impressions within the bovid brain cavity are theorized to mitigate headbutting injuries.

Purpose of the Study:

• To anatomically describe the muskox brain cavity.
• To quantify digitiform impressions and their relationship to headbutting behavior across bovids.
• To test the hypothesis that digitiform impressions protect the brain during head impacts.

Main Methods:

• Computed tomography (CT) scans of muskox and goat skulls were analyzed.
• A novel measurement, the endocranial roughness index (ERI), was developed to quantify digitiform impressions.
• The ERI was applied to a comparative sample of 59 bovid species.

Main Results:

• The muskox brain cavity was anatomically described for the first time.
• The study found no correlation between endocranial roughness and headbutting behavior across 59 bovid species.
• Quantitative assessment revealed no significant relationship between cranial features and head impacts.

Conclusions:

• Endocranial roughness, at the measured scale, does not appear to significantly protect the bovid brain during headbutting.
• The protective function of digitiform impressions may operate at a smaller, unmeasured scale.
• Evolutionary pressure does not appear to favor pronounced endocranial roughness for brain protection in headbutting bovids.