Natrix longivertebrata

Description. The basiphenoid is fragmentary. Its anterior portion, at the level of the anterior orifices of the Vidian canals approximately, is missing. The maximum width of the bone, measured between distal tips of the basipterygoid processes, is 3.7 mm. In ventral view, the basisphenoid crest is absent (Fig. 18 A, B). The basipterygoid processes are distinct. Their posterior margins are strongly extended posteriorly covering the recess housing the posterior foramina of the Vidian canals. However, a tiny proximal fragment of the left basipterygoid process is broken off, owing to which the posterior orifice of the Vidian canal as well as the cerebral foramen (for palatine branch of facial nerve, VII) are clearly visible in ventral view. In dorsal view, several foramina are visible, distributed typically of higher snakes (Fig. 18 C, D). The paired largest foramina, located at the midway between the posterior border of the bone itself and the posterior border of the pituitary fossa (sella turcica), are posterior openings for the abducens nerves (VI). The anterior openings for these nerves are situated near the postero-lateral corners of the pituitary fossa. The sympathetic nerve foramina (not visible on the right side) are located directly anterior to the pituitary fossa. The paired openings piercing the basipterygoid processes, laterally to the abducens nerve foramina, are tentatively interpreted as the deep petrosal nerve foramina (both visible on the left side only). Seen in left lateral view, an opening located directly above the posterior orifice of the Vidian canal and partly hidden beneath the basipterygoid process, is interpreted as a foramen for re-entry of the constrictor internus dorsalis branch (cid) of the trigeminal nerve (V 4) on its way from the prootic (Fig. 19 E, F). The location of the exit of the latter nerve (either within the basisphenoid or in a suture between the basisphenoid and parietal) remains unknown owing to the damage of the bone anterior to the basipterygoid processes.

Fig. 19

Material. One basisphenoid HLMD-Ez 2158.