Anguidae

Anguidae View in CoL View at ENA ( Fig. 12M–P, V View Figure 12 )

In European anguids, both anteromedial and anterolateral processes are pointed and well developed, defining a very deep and U-shaped anterior concavity that is also moderately narrow in dorsal view ( Fig. 12V View Figure 12 ). The two processes are slender and roughly similar in size in Anguis gr. An. fragilis , but the anteromedial process is slightly shorter than the anterolateral one in Pseudopus apodus . A well-developed lappet is present on the dorsal surface of the anteromedial process. In Anguis gr. An. fragilis , this lappet projects anteriorly beyond the end of the process with a pointed tip and bends slightly in medial direction ( Fig. 12V View Figure 12 ). The posterior process is long, slender and pointed in lateral view, lacking any step. The vomeronasal foramen is small (very small in Pseudopus apodus ) and opens in a shallow anteriorly concave area, bordered laterally and medially by two low ridges. The superior dental foramen is wide and continues posteriorly in a wide groove that runs along the dorsal surface of the posterior process. Teeth are large (maximum size is reached in the middle of the tooth row in Anguis gr. An. fragilis and by its posterior end in Pseudopus apodus ) and subpleurodont, lacking only on the posterior end of the maxilla. In Anguis gr. An. fragilis , they are monocuspid, trenchant, well-spaced and distinctly posterolingually bent by their tip ( Fig. 12M, N View Figure 12 ). Maxillae of Pseudopus apodus have two different tooth morphologies: anteriorly, they have monocuspid, cylindrical and slightly robust teeth, provided with a pointed and not curved tip, whereas on the posterior end there are very large, cylindrical and stout teeth, provided with a blunt and rounded crown ( Fig. 12O, P View Figure 12 ). Teeth of Pseudopus apodus are closely spaced and increase gradually in size posteriorly, but the last ones are smaller than the preceding ones. Striae are not present in Anguis gr. An. fragilis , but visible on both the lingual and the labial sides in Pseudopus apodus . The facial process is subtrapezoidal in lateral view, with a slightly convex dorsal margin and slightly concave anterior and posterior margins; the latter is almost vertical in Anguis gr. An. fragilis ( Fig. 12M, N View Figure 12 ) and slightly oblique in Pseudopus apodus ( Fig. 12O, P View Figure 12 ). The width of the process is smaller than half the length of the bone in Anguis gr. An. fragilis and roughly half the length in Pseudopus apodus . Both its anterodorsal and posterodorsal corners are rounded and a variable number of small foramina can be present near the former one. No dermal ornamentation is present on the lateral surface of the facial process in Anguis gr. An. fragilis ( Fig. 12M View Figure 12 ), whereas a very light one is visible in Pseudopus apodus ( Fig. 12O View Figure 12 ). The medial surface has a thickened area on the anterior margin and a low (sometimes more distinct in Anguis gr. An. fragilis ) arched ridge, similar to the one present in lacertids and scincids. The maximum length of the alveolar border goes from 3.3 mm to 7 mm in Anguis gr. An. fragilis and from 12.5 mm to 16.6 mm in Pseudopus apodus , whereas the number of tooth positions is nine in Anguis gr. An. fragilis and goes from nine to 14 in Pseudopus apodus . Three or four ventrolateral foramina are present in Anguis gr. An. fragilis , three, four or five in Pseudopus apodus .

PREFRONTAL

The paired prefrontal ( Fig. 14 View Figure 14 ) has an anteriorly concave body, named the orbitonasal flange. The large and pointed dorsal process starts from the medial side of the dorsal margin of the flange, extending in the posterodorsal direction. The laminar anterodorsal process develops in anterior direction from the orbitonasal flange and a posteroventral process develops ventrolaterally from its ventrolateral corner. A small posterolaterally directed projection is present at the tip of the posteroventral process. A wide notch of the lacrimal foramen is located between the anterodorsal and the posteroventral processes.