Anguidae

Villa, Andrea & Delfino, Massimo, 2019, A comparative atlas of the skull osteology of European lizards (Reptilia: Squamata), Zoological Journal of the Linnean Society 187 (3), pp. 828-928 : 846-847

Anguidae ( Fig. 9E–J )

In European anguids, the premaxilla has a wide and low alveolar plate. In Anguis gr. An. fragilis , the ascending nasal process is short and very narrow by its base, but it presents a wide and lobe-shaped dorsal-half, provided with a pointed end ( Fig. 9E, F ). In Pseudopus apodus , on the other hand, it is moderately wide, with straight and parallel lateral margins and a rounded dorsal end ( Fig. 9I, J ). However, according to Klembara et al. (2017) the process of young Pseudopus apodus is slightly widened at midlength. The anterior surface of the process is smooth ( Fig. 9E, I ), whereas only in Anguis gr. An. fragilis a low but distinct septonasal crest runs along the posterior one ( Fig. 9F ). The development of the crest increases during growth, being unrecognizable in juveniles. Each palatal process is split into two portions by a deep notch ( Fig. 9H ): laterally there is the narrow maxillary process, provided with a roughly rounded end, whereas the pointed and slightly wider vomerine process is present medially. The two vomerine processes are not fused medially, but they are flanked and present a wide notch between them. The ventral end of the septonasal crest splits into two prominent ridges that merge into the dorsal surface of the vomerine processes ( Fig. 9F ). These ridges are present also in Pseudopus apodus , even if the crest is not present in this species ( Fig. 9J ). A well-developed incisive process is present: it is composed of two lobe-shaped and ventrally concave portions located on the ventral surface of the vomerine processes ( Fig. 9H ). Teeth are subpleurodont, slender (slightly thicker in Pseudopus apodus ), monocuspid and slightly posteriorly curved by their tip. They are roughly subcylindrical, but the pointed tip gives them a more trenchant shape [morphotype A sensu Kosma (2004)] in Anguis gr. An. fragilis ( Fig. 9E, F ). Teeth of Pseudopus apodus have a blunter tip ( Fig. 9I, J ). No striation is visible on the crown of the teeth of Anguis gr. An. fragilis , whereas distinct striae are visible on both the labial and the lingual sides in Pseudopus apodus . The number of tooth positions is nine in Anguis gr. An. fragilis and goes from six to seven [seven to nine following Roček (1980) and Klembara et al. (2017)] in Pseudopus apodus , whereas the maximum width of the alveolar plate varies from 1.4 mm to 2.9 mm in Anguis gr. An. fragilis and from 5 mm to 5.5 mm in Pseudopus apodus .

MAXILLA

The paired maxillae ( Figs 11 , 12 ) consist of an alveolar portion and a dorsomedially developed facial process. The alveolar portion is composed by a tooth-bearing alveolar border and by a palatal shelf developed medially. The anterior end (anterior premaxillary process) has a concave anterior margin due to the presence of the anteromedial and anterolateral processes. The posterior end corresponds to an elongated posterior process. The maxilla is crossed by the superior alveolar canal, which runs through the base of the facial process. Its anterior opening, the vomeronasal foramen, is located on the dorsal surface of the premaxillary process. The posterior opening, on the other hand, is the wide superior dental foramen [infraorbital foramen in Barahona (1996)] and opens on the dorsal surface of the palatal shelf. Lateral openings of the canal are represented by the ventrolateral (labial) foramina, whose number is highly variable, even in the two maxillae of the same specimen.

Figures

Figure 9. Premaxillae (continued) – A–D, Chalcides ocellatus (MDHC 250), right premaxilla in anterior (A), posterior (B), dorsal (C) and lateral (D) views. E–H, Anguis gr. An. fragilis (MDHC 102), premaxilla in anterior (E), posterior (F), left lateral (G) and ventral (H) views. I–J, Pseudopus apodus (MDHC 215), premaxilla in anterior (I) and posterior (J) views (the right side of the alveolar plate is broken). Abbreviations: ip, incisive process; mp, maxillary process; n, notch; pp, palatal process; sc, septonasal crest; vp, vomerine process. Scale bars = 1 mm.

Figure 11. Maxillae – A–B, Laudakia stellio (HUJ.OST-Z-423), left maxilla in lateral (A) and medial (B) views (the maxilla is broken and lacks part of the tooth row). C, Laudakia stellio (HUJ.OST-Z-5), articulated right maxilla in lateral view. D–E, Chamaeleo chamaeleon (NHMW 611), right maxilla in lateral (D) and medial (E) views. F–G, Ac. erythrurus (UAM.R.ACVII), left maxilla in lateral (F) and medial (G) views. H–I, Lacerta bilineata (MDHC 15), right maxilla in lateral (H) and medial (I) views. J, Lacerta bilineata (MDHC 381), right maxilla in lateral view. K–L, Po. melisellensis (NHMW 628), left maxilla in lateral (K) and medial (L) views. M–N, Psammodromus algirus (UAM.R.Ps9), left maxilla in lateral (M) and medial (N) views. O, Ti. lepidus (NHMW 625), right maxilla of a juvenile individual in medial view. Abbreviations: ab, alveolar border; adp, anterior dorsal process; alp, anterolateral process; amp, anteromedial process; ap, alveolar portion; app, anterior premaxillary process; ar, arched ridge; fp, facial process; l, lappet; pp, posterior process; ppj, posterodorsal projection; ps, palatal shelf; r, ridge; sp, spur; vlf, ventrolateral foramen. Scale bars = 1 mm.

Figure 12. Maxillae (continued) – A–B, Z. vivipara (UAM.R.Lv24), left maxilla in lateral (A) and medial (B) views. C–D, Ab. kitaibelii (MDHC 239), left maxilla in lateral (C) and medial (D) views. E–F, Chalcides chalcides (MDHC 398), right maxilla in lateral (E) and medial (F) views. G–H, Chalcides ocellatus (MDHC 250), right maxilla in lateral (G) and medial (H) views. I–J, Ophiomorus punctatissimus (MDHC 427), left maxilla in lateral (I) and medial (J) views. K–L, Tr. aurata (MDHC 280), right maxilla in lateral (K) and medial (L) views. M–N, Anguis gr.An. fragilis (MDHC 102), right maxilla in lateral (M) and medial (N) views. O–P, Pseudopus apodus (MDHC 215), left maxilla in lateral (O) and medial (P) views (the anterior tip of the anteromedial process is broken and there is a pathologically-growth tooth). Q, Ac. erythrurus (UAM.R.ACVII), left maxilla in dorsal view. R, Lacerta bilineata (MDHC 381), right maxilla in dorsal view. S, Chalcides chalcides (MDHC 398), right maxilla in medial view.T, Chalcides ocellatus (MDHC 250), right maxilla in dorsal view. U, Ophiomorus punctatissimus