The braincase of Typhlops and Leptotyphlops (Reptilia: Serpentes)

The structure of the braincases and associated nerves and blood-vessels is described. Typhlops combines primitive lacertilian features, notably the retention of a palatine artery, with specialisations such as the structure of the recessus scalae tympani. Leptotyphlops is more completely snake-like, but the two genera show in common a specialised intracranial course of the hyomandibular branch of the facial nerve, due to lateral closure of the juxtastapedial recess by the overgrowing crista circumfenestralis. The lateral closure of the juxtastapedial recess is considered as an adaptation to burrowing habits. The Vidian canal in scolecophidians is poorly defined, due to the lack of lateral ascending wings of the parasphenoid. This might constitute an archaic character contradicting the descent of snakes from any Recent lacertilian group.