Exceptional preservation informs the paleobiology of tapinocephalid dinocephalians.

The tapinocephalid dinocephalian Moschops is one of the most iconic taxa of the middle Permian, yet its paleobiology remains one of the least well-known. Here, we address some aspects of paleoneurology and paleobiology of Moschops using CT scanning of four well preserved skulls from the upper Abrahamskraal Formation of South Africa. Two of the specimens preserve articulated scleral ossicle rings, the dimensions of which are more consistent with a diel activity pattern, although intermediate between diurnal, nocturnal, and cathemeral. The bony labyrinth for the inner ear (preserved in one specimen) has comparatively short semicircular canals, and the agility score aligns with those of modern large herbivores that are able to swim. This is consistent with previous hypotheses inferring that some tapinocephalid dinocephalians may have been semi-aquatic. The four individuals form a partial ontogenetic series, and we show that the endocast grows markedly with body size in Moschops, as does the encephalization quotient. The latter is an unusual pattern for vertebrates. We also report the first possible evidence for the preservation of soft brain tissues in a non-mammalian synapsid, which sparks exciting perspectives for future studies of non-mammalian synapsid paleoneurology.