Anguidae

Anguidae View in CoL View at ENA ( Figs 34 View Figure 34 , 37R, S View Figure 37 )

The basipterygoid processes are axe-shaped and short in the sphenoid of anguids. Their proximal half is strongly enlarged, almost reaching the width of the distal end. The latter is expanded, almost flattened and almost horizontal in anterior view, whereas it is slightly convex in dorsal view. Very long cristae ventrolaterales are present on the posterolateral corners of the bone. The trabeculae are well developed and robust, projecting beyond the anterior margin of the bone; the midline contact between them is a very variable feature both in Anguis gr. An. fragilis and Pseudopus apodus . The cristae trabeculares are also well developed. A well-developed rostrum develops between the trabeculae. The sella turcica is very wide and smooth; it is covered by a well-developed dorsum sellae. The ventral surface of the sphenoid is rather flattened, with only a slightly sunken area in the middle. In European anguids, the Vidian canals continue posteriorly and their posterior opening is located on the prootics. However, the lateral wall of this posterior portion of the canals is still composed of the sphenoid, because they are covered by the cristae ventrolaterales. A laminar supravenous process similar to the one of lacertids and scincids develops anteriorly from each alar process of the crista sellaris. As in the latter families, it is not clear if this process can be considered homologous with that of gekkotans, but the merging of the crista prootica into them seems to suggest so. These processes are narrower and more rounded anteriorly in Anguis gr. An. fragilis ( Fig. 34B View Figure 34 ), whereas they are larger and more squared in Pseudopus apodus ( Fig. 34G View Figure 34 ). A wide and moderately deep groove for the lateral head vein is visible ventrally to them, being marked ventrally by a low ridge located on the dorsal surface of the proximal end of the basipterygoid processes. Sometimes, the anterior part of this ridge can form a dorsally directed expansion that comes close to the related supravenous process.

SUPRAOCCIPITAL

The unpaired supraoccipital ( Fig. 38 View Figure 38 ) includes the epiotic of Jollie (1960). This bone is elongated transversely and posteriorly inclined. It can be separated into three portions: a thin medial portion and two wide lateral portions. The latter form the roof of each cavum capsularis. Posteriorly the supraoccipital represents the dorsal margin of the foramen magnum. Anteriorly, it can carry an anterodorsally developed processus ascendens or other different structures. The anterior margin of the bone hosts the dorsal portions of the anterior semicircular canals. The dorsal portions of the posterior semicircular canals run from the posterolateral corners to the middle of the dorsal surface of the bone. Anterior and posterior canals merge in the common crus, which in turn opens to the cavum capsularis. The endolymphatic foramina are present near the contact with the prootic, on the medial surface of each lateral portion of the supraoccipital. This foramina opens posterodorsally and are moderately wide. The supraoccipital is fused with the prootics and the otooccipitals.