2017/08/10 by Julien Benoît, Paul R. Manger, Luke A. Norton +2 · 1 citation
Earth and Planetary Sciences · Environmental Science · #Evolution and Paleontology Studies #Paleontology and Evolutionary Biology #Amphibian and Reptile Biology
paper · doi:10.7717/peerj.3496
openalex publication_date 2017/08/10 · openalex created_date 2017/08/17 · openalex updated_date 2026/06/23
reveals, for the first time, numerous anatomical adaptations of the central nervous system related to this combative behaviour. Many neural structures (such as the brain, inner ear and ophthalmic branch of the trigeminal nerve) were completely enclosed and protected by bones, which is unusual for non-mammaliaform therapsids. The nearly complete ossification of the braincase enables precise determination of the brain cavity volume and encephalization quotient, which appears greater than expected for such a large and early herbivore. The practice of head butting is often associated with complex social behaviours and gregariousness in extant species, which are known to influence brain size evolution. Additionally, the plane of the lateral (horizontal) semicircular canal of the bony labyrinth is oriented nearly vertically if the skull is held horizontally, which suggests that the natural position of the head was inclined about 60-65°to the horizontal. This is consistent with the fighting position inferred from osteology, as well as ground-level browsing. Finally, the unusually large parietal tube may have been filled with thick conjunctive tissue to protect the delicate pineal eye from injury sustained during head butting.