Endocranial casts of early archosaurian reptiles

The first endocranial casts from non-crown-group archosaurian reptiles are described. Synthetic casts were made of the preserved parts of the endocranial cavities ofErythrosuchus africanus,Vjushkovia triplicostata andXilousuchus sapingensis. These casts are incomplete, but they reveal a substantial amount of information on the form of the early archosaur brain and inner ear. Cranial and pontine flexures are equal in bothErythrosuchus (45°) andV. triplicostata (35–40°). The endocasts ofXilousuchus andV. triplicostata are characterised by the possession of a pseudolagena and a quantifiable down-slope from the myelencephalon to the metencephalon — features that have yet to be described for other reptilian endocranial casts.