Anguidae

Anguidae View in CoL View at ENA ( Fig. 47O–R View Figure 47 )

The coronoid of anguids is straight (but slightly medially concave) in dorsal view (Fig. 48D). The coronoid process is moderately thin ( Anguis gr. An. fragilis ; Fig. 47O, P View Figure 47 ) or distinctly robust ( Pseudopus apodus ; Fig. 47Q, R View Figure 47 ), dorsally rounded and posteriorly directed. In the articulated lower jaw, this process is covered more extensively by the superior posterior process of the dentary in Pseudopus apodus than it is in Anguis gr. An. fragilis (see: Klembara et al., 2014): the process of the dentary runs up to half the height of the coronoid process in the former taxon, whereas it only covers a short part of it in the latter. The anteromedial process is represented by a horizontal and slender lamina, lacking any foramina and, at least in Anguis gr. An. fragilis , provided with a pointed and moderately developed projection at its anterior end ( Fig. 47O, P View Figure 47 ). In Pseudopus apodus , the anterior end of this process defines the anterior inferior foramen, as can be clearly seen in articulated specimens ( Klembara et al., 2014). In Anguis gr. An. fragilis , the process is excluded from the foramen by the dentary and the splenial ( Klembara et al., 2014). The labial process is short in Pseudopus apodus ( Fig. 47Q View Figure 47 ), but distinctly longer in Anguis gr. An. fragilis ( Fig. 47O View Figure 47 ). The posterior process is very short (often lacking in smaller individuals) and is represented only by a small projection on the dorsal margin of the posteromedial process, defining a small and shallow notch on the posterior end of the coronoid. The degree of development of the posterior process is higher in Pseudopus apodus ( Fig. 47Q, R View Figure 47 ) than in Anguis gr. An. fragilis ( Fig. 47O, P View Figure 47 ). The posteromedial process is long, slender and can be lobe-shaped or pointed. In anguids, this process develops more posteriorly than ventromedially. A well-developed and laminar coronoid ridge, similar to the lamina of gekkotans ( Villa et al., 2018a), is present between the coronoid and the posteromedial processes. The laminar ridge of Pseudopus apodus ( Fig. 47Q, R View Figure 47 ) is thicker and slightly less developed than the one of Anguis gr. An. fragilis ( Fig. 47O, P View Figure 47 ), being also less distinguishable from the coronoid process.

ANGULAR, SURANGULAR, PREARTICULAR AND ARTICULAR

These four bones ( Figs 49 View Figure 49 , 50 View Figure 50 , 51 View Figure 51 ) compose the posterior portion of the mandible, enclosing the posterior portion of the Meckel’s cartilage. They can fuse completely or partially to form a compound bone. The angular is a laminar and elongated bone, composing the ventrolateral wall of this portion of the mandible. The elongate surangular is located dorsally and contributes to the formation of the dorsal and lateral walls of the mandible. At the middle of its length it is expanded and displays a slightly irregular and sunken dorsomedial surface. Another laminar expansion is present near the posterior end. This second expansion is arched and encircles the articular condyle of the articular. Two foramina can be seen in lateral view: the anterior surangular foramen and the posterior surangular foramen. The former is located near the dorsal margin of the bone at the anterior expanded area, whereas the latter is placed near the ventral margin at the posterior expansion.The prearticular and the articular are always fused in a single and straight bone composing the ventral wall of the mandible. This bone has a pointed anterior end and expands dorsally by the second-fourth of its length, forming a projection that contacts the surangular. The posterior end of the bone presents the articular condyle with the quadrate dorsally and the retroarticular process posteriorly. The condyle is wide and subcircular or subquadrangular; the articulation surface is directed posteromedially and bears two slightly sunken areas separated by a low median ridge. The retroarticular process is usually long and wide. It is dorsomedially concave and bears a foramen for the chorda tympani near the anteroventral corner of the medial surface. An angular process can develop in the medial direction ventrally to the condyle. Medially, the broad adductor fossa is present anteriorly to the articular condyle. The fossa is defined by the surangular dorsally and by the prearticular/articular complex ventrally.