Lacertidae

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 : 854

Lacertidae ( Fig. 16E–L )

In the jugal of lacertids, the anterior process can be narrow and pointed (most species; Fig. 16I–L ), moderately large, flattened and more rounded anteriorly ( Ac. erythrurus ; Fig. 16E, F ) or moderately large, flattened and anteriorly forked ( Ophisops elegans ; Fig. 16G, H ). The lateral surface of the anterior portion of this process is largely covered by the articulation surface with the posterior process of the maxilla ( Fig. 16I, K ), except for Ac. erythrurus and Ophisops elegans , in which this surface is narrow and the bone is more laterally exposed ( Fig. 16E, G ). In species in which either a step or a spur is present on the dorsal margin of the posterior process of the maxilla (see above), the articulation surface on the jugal recalls the stepped and spurred morphology, respectively. The palatal process is present: it is weakly developed in Ac. erythrurus ( Fig. 16F ), E. arguta and Ophisops elegans ( Fig. 16H ), and moderately to well developed in other species ( Fig. 16J, L ). A distinct medial process is present in Ophisops elegans ( Fig. 16H ) and Psammodromus ( Figs 16J , 17A ), but a poorly developed one ( Fig. 17B ) can be also present in other genera [e.g. Podarcis , as also reported by Blain et al. (2007)]. The posterodorsal process is narrow and pointed. Proportions of the anterior and posterodorsal processes differ within species: the anterior one is the longest in Algyroides , Da. oxycephala , Di. mosorensis , Lacerta agilis , Lacerta bilineata , Lacerta schreiberi , Lacerta viridis , Ophisops elegans , Po. siculus , Po. tauricus , Po. tiliguerta , Po. waglerianus , Psammodromus algirus , Z. vivipara and some specimens of Po. muralis ( Fig. 16G–J ), the posterodorsal one is the longest in Ac. erythrurus and E. arguta ( Fig. 16E, F ), whereas they have roughly the same length in Ar. bedriagae , H. graeca , I. bonnali . I. cyreni , I. horvathi , I. monticola , Lacerta trilineata , Po. bocagei , Po. filfolensis , Po. hispanicus , Po. lilfordi , Po. melisellensis , Po. milensis , Po. pityusensis , Ti. lepidus and some specimens of Po. muralis ( Fig. 16K, L ). A certain degree of ontogenetic variation can be present, as demonstrated by Ti. lepidus NHMW 625, a very young individual whose anterior process is clearly longer than the posterodorsal one ( Fig. 18 ). The quadratojugal process can be absent ( Ac. erythrurus and Ophisops elegans ; Fig. 16E–H ), weakly developed ( I. horvathi , Po. pityusensis , Po. tiliguerta and Psammodromus algirus ; Fig. 16I, J ) or well developed (other species; Fig. 16K, L ). Its development may vary during ontogeny, being more developed in juveniles and less developed in adults (e.g. Psammodromus algirus ; Barahona & Barbadillo, 1997). The lateral surface of the ventral portion of the bone can be covered, at least in large specimens, by a moderately to well-developed dermal ornamentation (absent in Ac. erythrurus , Algyroides , Da. oxycephala , Di. mosorensis , E. arguta , H. graeca , I. bonnali , I. cyreni , I. horvathi , I. monticola and Ophisops elegans ). A moderately large foramen opens on the medial surface of the jugal, at the meeting point of the anterior and the posterodorsal processes.

Figures

Figure 16. Jugals – A–B, Laudakia stellio (HUJ.OST-Z-424), left jugal in lateral (A) and medial (B) views. C–D, Chamaeleo chamaeleon (NHMW 611), left jugal in lateral (C) and medial (D) views. E–F, Ac. erythrurus (UAM.R.ACVII), left jugal in lateral (E) and medial (F) views (the dorsal margin of the anterior process is damaged). G–H, Ophisops elegans (MDHC 281), left jugal in lateral (G) and medial (H) views. I–J, Psammodromuss algirus (UAM.R.Ps9), right jugal in lateral (I) and medial (J) views. K–L, Ti. lepidus (MDHC 216), right jugal in lateral (K) and medial (L) views. M–N, Ab. kitaibelii (MDHC 239), right jugal in lateral (M) and medial (N) views. O–P, Chalcides chalcides (MDHC 398), left jugal in lateral (O) and medial (P) views. Q–R, Ophiomorus punctatissimus (MDHC 427), left jugal in lateral (Q) and medial (R) views. S–T, Anguis gr. An. fragilis (MDHC 102), right jugal in lateral (S) and medial (T) views. U–V, Pseudopus apodus (MDHC 215), left jugal in lateral (U) and medial (V) views. Abbreviations: ap, anterior process; asm, articulation surface with the maxilla; aspo, articulation surface with the postorbital; mp, medial process; pdp, posterodorsal process; pp, palatal process; qjp, quadratojugal process. Scale bars = 1 mm.

Figure 17. Dorsal view of theright jugal of Psammodromus algirus (UAM.R.Ps9) (A), Ti. lepidus (MDHC 216) (B) and Anguis gr.An. fragilis (MDHC 102) (C), displaying different developments of the medial process (white arrows): well developed (A), poorly developed/almost indistinct (B) and absent (C). Scale bars = 1 mm.

Figure 18. Right jugal of NHMW 625, a young individual of Ti. lepidus, in medial view. Note the anterior process, which is longer than the posterodorsal one. Scale bar = 1 mm.