Anguidae

Anguidae View in CoL View at ENA ( Fig. 34 View Figure 34 )

The supraoccipital of anguids has a well-developed, cylindrical and slightly dorsoventrally compressed processus ascendens, whose degree of ossification increases with growth. A low supraoccipital crest is present, but less developed in juveniles. The rest of the dorsal surface of the bone is smooth because of the poor development of the semicircular canals. Lateral crests similar to those present in lacertids run along the anterior margin of the supraoccipital in anguids too, flanking the processus ascendens. These crests are well developed in adults (sometimes reaching the distal end of the processus), but lower in juveniles. A distinct, roughly V-shaped and rounded notch is clearly visible in the middle of the posterior margin in dorsal view.

PROOTIC

The paired prootic ( Fig. 40 View Figure 40 ) includes a posterior process (posteriorly), an alar process (anterodorsally) and an anterior inferior process (ventrally). The horizontal semicircular canal and, anterodorsally to the latter, the anterior semicircular canal occupy the posterior process. Posteriorly, this process develops a projection that extends to cover the anterior surface of the paroccipital process of the otooccipital. The alar process extends from the anterodorsal end of the anterior semicircular canal, bearing the articulation surface with the epipterygoid on its anterior margin, which is named crista alaris. The anterior inferior process displays the incisura prootica, the facial foramen and the laminar crista prootica. The incisura prootica is broad and located medioventrally to the alar process. The facial foramen opens both to the lateral and medial surfaces, and ventrally to the horizontal semicircular canal and the crista prootica. The crista prootica runs anteroventrally, starting from the ventral end of the anterior semicircular canal. It continues also on the posterior process, curving posteriorly and becoming a ridge that runs ventrally to the horizontal semicircular canal. The posterior portion of the recessus vena jugularis runs ventrally to the crista prootica. Two other large foramina are visible medially, opening in a concave acoustic recess. These foramina are the smaller anterior acoustic foramen and the very large posterior acoustic foramen. The former is located dorsally to the facial foramen and opens in the ampullary recess, whereas the latter is placed slightly posteriorly and opens internally between the cochlear cavity and the cavum capsularis. These two foramina carry the branches of the vestibulocochlear nerve. The prootic encloses the anterior portion of the inner ear. Its inner structures include the anterior portions of the cavum capsularis dorsally, that of the cochlear cavity ventrally and the cochlear crest between them. The opening of the anterior semicircular canal flanks dorsally the cavum capsularis, whereas laterally to the latter there is the opening of the horizontal semicircular canal. The opening of the ampullary recess is visible at the medioventral corner of the cavum. The dorsal-half of the anterior wall of the cochlear cavity houses the wide groove for the perilymphatic duct. The prootic fuses with the sphenoid anteroventrally, the basioccipital posteroventrally, the supraoccipital posterodorsally and the otooccipital posteriorly.