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 : 840-841

Lacertidae ( Figs 5E–N , 6F )

Lacertids have an unpaired parietal, with a weakly ( Al. marchi , I. bonnali , I. horvathi , Po. filfolensis and Z. vivipara ; Fig. 5M, N ) or strongly interdigitated (other species; Fig. 5G, H, K, L ) anterior margin. The interdigitations are absent in Ac. erythrurus and generally in Ophisops elegans , whose anterior margin is wavy and presents a concavity in the middle ( Fig. 5E, F, I, J ). The table is larger than it is long in Ac. erythrurus , E. arguta , I. horvathi , Ophisops elegans shield; ls, lateral shield; mvc, medial ventral crest; os, occipital shield; pc, parietal crest; pfr, parietal foramen; pfs, parietal fossa; pn, parietal notch; pot, posterior tab; pp, posterior process; ps, posterior section of the posterolateral ventral crest; pt, parietal tab; pvc, posterolateral ventral crest; r, ridge; sl, suture line; stp, supratemporal process; t, parietal table; tp, triangular process. Scale bars = 1 mm.

and Z. vivipara ( Fig. 5E, F, I, J, M, N ), whereas it is longer in the other species ( Fig. 5G, H, K, L ). Anterolateral processes are anteriorly pointed, usually bifurcated ( Barahona, 1996), and distinctly developed in anterior direction to form parietal tabs. The degree of development of the tabs is linked to age and size, with adults and larger species having more developed ones. In Ac. erythrurus , E. arguta and Ophisops elegans they are also expanded laterally ( Fig. 5E, F, I, J ). The morphology of the supratemporal processes varies: they are thin in Ac. erythrurus , Al. marchi , Al. moreoticus , Di. mosorensis , E. arguta , I. bonnali , Ophisops elegans , Po. siculus , Po. hispanicus and Z. vivipara ( Fig. 5E, F, I, J, M, N ), whereas they widen proximally in Al. fitzingeri (Wiegmann, 1834) , Al. nigropunctatus , Ar. bedriagae , Da. oxycephala , H. graeca , I. cyreni , I. horvathi , I. monticola , Lacerta , Po. bocagei , Po. filfolensis , Po. hispanicus , Po. lilfordi , Po. melisellensis , Po. milensis , Po. muralis , Po. pityusensis , Po. tauricus , Po. tiliguerta , Po. waglerianus , Psammodromus algirus (Linnaeus, 1758) and Ti. lepidus ( Fig. 5G, H, K, L ). A well-developed dermal ornamentation, the development of which increases in older individuals and larger species, is present on the dorsal surface of the table, but not on the processes. The two frontoparietal (anteriorly), the interparietal (in the middle of the table), the two lateral (laterally) and the occipital (posteriorly) shields are recognizable because of the presence of the grooves marking their borders on the ornamentation. Acanthodactylus erythrurus , E. arguta and Ophisops elegans have a less-developed ornamentation ( Fig. 5E, I ). The two former species lack the occipital shield, whereas a small one is present in Ophisops elegans ( Fig. 5I ). In Ti. lepidus the latter shield is very large ( Figs 5K , 7 ). An area levis devoid of ornamentation is present on the parietal table of Ac. erythrurus , I. horvathi , Ophisops elegans , Ps. hispanicus and Z. vivipara ( Fig. 5E, I, M ), whereas in other species the ornamentation reaches the posterior margin (at least in adults). Five ventral crests are present on the ventral surface: a medial one in the middle of the table, two anterolateral ones running posteromedially from each anterolateral corner of the table and two posterolateral ones running anteromedially along the ventral surface of the supratemporal processes. The crests are moderately low in small species ( Fig. 5F, J, N ) and in juveniles of the largest ones, but they can grow to become sharp and well developed in adults of the latter ( Fig. 5H, L ). The deep (shallower in juveniles) parietal fossa is visible posteriorly to the medial ventral crest. Anterolateral ventral crests always touch the medial one, whereas a contact between the former and the posterolateral ones is absent in adults of Al. fitzingeri , Al. nigropunctatus , H. graeca , Lacerta , Po. filfolensis , Po. melisellensis , Po. milensis , Po. muralis [in contrast to what was stated by Barahona (1996) and Barahona & Barbadillo (1997)], Po. pityusensis , Po. siculus , Po. tauricus , Po. tiliguerta , Po. waglerianus , Psammodromus algirus and Ti. lepidus ( Fig. 5H, L ), and present in juveniles of the previously cited species, as well as in both adults and juveniles of other ones ( Fig. 5F, J, N ). It has to be noted that the contact is also present in some adult specimens of Lacerta agilis Linnaeus, 1758 (MDHC 178) and Po. melisellensis (MDHC 217, 218 and NHMW 650), suggesting that variation may rarely be present, at least in these species. The parietal fossa is wide and U-shaped in Ac. erythrurus , Algyroides , Ar. bedriagae , Da. oxycephala , H. graeca , I. bonnali , I. cyreni , I. monticola cantabrica , Ophisops elegans , Po. bocagei , Po. carbonelli , Po. filfolensis , Po. hispanicus , Po. lilfordi , Po. melisellensis , Po. milensis , Po. siculus , Po. tauricus , Po. tiliguerta , Po. waglerianus , Ps. hispanicus and Z. vivipara ( Fig. 5F, J, N ), narrow and U-shaped in I. monticola monticola , Lacerta schreiberi , Lacerta viridis , Po. pityusensis , Psammodromus algirus and juveniles of Po. muralis , triangular in Lacerta bilineata , Lacerta trilineata , Ti. lepidus and adults of Po. muralis ( Fig. 5H, L ). Lacerta agilis can have either a narrow or a wide U-shaped fossa. A parietal notch is present in juveniles of all species and is retained in adults of Ac. erythrurus , Al. marchi , Ophisops elegans , Ps. hispanicus and Z. vivipara ( Fig. 5E, I, M ), whereas in adults of the other species the posterior margin is straight ( Fig. 5G, K ). A wide and either subcircular or subelliptical parietal foramen is present in the middle of the table. Measurements are given in the Supporting Information 3.

Figures

Figure 5. Parietals – A–B, Laudakia stellio (MDHC 245), parietal in dorsal (A) and ventral (B) views. C–D, Chamaeleo chamaeleon (NHMW 611), parietal in dorsal (C) and ventral (D) views. E–F, Ac. erythrurus (UAM.R.ACVII), parietal in dorsal (E) and ventral (F) views. G–H, Lacerta schreiberi (UAM.R.S-6), parietal in dorsal (G) and ventral (H) views. I–J, Ophisops elegans (MDHC 281), parietal in dorsal (I) and ventral (J) views. K–L, Ti. lepidus (MDHC 216), parietal in dorsal (K) and ventral (L) views. M–N, Z. vivipara (UAM.R.Lv24), parietal in dorsal (M) and ventral (N) views. O–P, Ab. kitaibelii (MDHC 239), parietal in dorsal (O) and ventral (P) views. Q–R, Chalcides chalcides (MDHC 398), parietal in dorsal (Q) and ventral (R) views. S–T, Chalcides ocellatus (MDHC 250), parietal in dorsal (S) and ventral (T) views. U–V, Ophiomorus punctatissimus (MDHC 427), parietal in dorsal (U) and ventral (V) views.W–X, Tr. aurata (MDHC 280), parietal in dorsal (W) and ventral (X) views. Y–Z, Anguis gr. An. fragilis (MDHC 102), parietal in dorsal (Y) and ventral (Z) views. Abbreviations: al, area levis; alp, anterolateral process; as, anterior section of the anterolateral ventral crest; aspa, articulation surface with the processus ascendens of the supraoccipital; avc, anterolateral ventral crest; fps, frontoparietal shield; ips, interparietal

Figure 6. Parietals (continued) – A–B, Pseudopus apodus (MDHC 214), parietal in dorsal (A) and ventral (B) views (supratemporal processes are broken). C, Pseudopus apodus (PIMUZ A/III0975), parietal in dorsal view. D, Laudakia stellio (MDHC 245) in right lateral view. E, Chamaeleo chamaeleon (NHMW 611), parietal in right lateral view. F, Lacerta bilineata (MDHC 381), parietal in left lateral view. G, Chalcides ocellatus (MDHC 250), parietal in left lateral view. H, Ophiomorus punctatissimus (MDHC 427), parietal in left lateral view. I, Tr. aurata (MDHC 280), parietal in left lateral view. J, Anguis gr. An. fragilis (MDHC 102), parietal in left lateral view. K, Pseudopus apodus (MDHC 214), parietal in right lateral view (supratemporal processes are broken). Abbreviations: al, area levis; as, anterior section of the anterolateral ventral crest; aslf, articulation surface with the lappet of the frontal; ca, carina arcuata; ep, epipterygoid process; fps, frontoparietal shield; l, lappet; mc, median crest; pc, parietal crest; pfs, parietal fossa; ps, posterior section of the posterolateral ventral crest. Scale bars = 1 mm.

Figure 7. Articulated parietal of Ti. lepidus (MNHN 1991.4242) in dorsal view. Scale bar = 1 mm.