Scincidae

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 : 837

publication ID	https://doi.org/10.1093/zoolinnean/zlz035
persistent identifier	https://treatment.plazi.org/id/9C298799-D24A-5A32-FF2D-FD3B257EA981
treatment provided by	Plazi
scientific name	Scincidae
status

Treatment

Scincidae View in CoL ( Figs 2R–Y View Figure 2 , 3A, B, I–L View Figure 3 )

In European scincids, the frontal can be either unfused, having no clear constriction in the middle ( Chalcides and Ophiomorus punctatissimus ; Fig. 2T–Y View Figure 2 ), or fused, with a weak ( Tr. aurata ; Fig. 3A, B View Figure 3 ) or stronger ( Ab. kitaibelii ; Fig. 2R, S View Figure 2 ) middle constriction. In all species except Ophiomorus punctatissimus the posterior end is about twice as large as the rest of the bone and so, when paired, the latter is roughly L-shaped in dorsal view. Because of the poor development of the posterolateral process, the frontal of Ophiomorus punctatissimus widens only slightly posteriorly ( Fig. 2X, Y View Figure 2 ). When fused, the suture line is still visible in ventral view on the anterior-half of the resulting bone ( Fig. 3A View Figure 3 ). As in lacertids, short medial and lateral processes are present on the anterior end and are separated by a moderately shallow concavity, but, in contrast with them, the lateral one is not bifurcated. The only exception is Tr. aurata , whose lateral processes are represented by short and wide flanges, with an irregular anterior margin made of more or less pointed expansions ( Fig. 3A, B View Figure 3 ). In Ab. kitaibelii and Ophiomorus punctatissimus , the lateral processes are little developed, in contrast with the distinctly developed medial ones ( Fig. 2R, S, X, Y View Figure 2 ). Low ridges (strongly more distinct in Tr. aurata ; Fig. 3A View Figure 3 ) mark the margins of the articulation surface with the nasal, which is subtrapezoidal ( Ab. kitaibelii , Chalcides chalcides and Ophiomorus punctatissimus ; Fig. 2R, X View Figure 2 ) or rounded ( Chalcides ocellatus , Chalcides striatus and Tr. aurata ; Figs 2T, V View Figure 2 , 3A View Figure 3 ) in shape. The articulation surface with the prefrontal is long and large. It reaches half the length of the bone (the posterior third in Ophiomorus punctatissimus ; Fig. 3L View Figure 3 ), but it does not touch the smaller and shorter (very short in Ab. kitaibelii ; Fig. 3I View Figure 3 ) articulation surface with the postfrontal. However, in Chalcides ocellatus and Ophiomorus punctatissimus these two articulation surfaces are close to each other ( Fig. 3K, L View Figure 3 ); they can also contact each other in the latter species (e.g. MDHC 427; Fig. 3L View Figure 3 ). The posterolateral process is moderately short (even shorter in Ophiomorus punctatissimus ; Fig. 2X, Y View Figure 2 ) and wide, with a rounded or pointed distal end (in dorsal view); the process is slightly longer and more slender in Ab. kitaibelii ( Fig. 2R, S View Figure 2 ) and Tr. aurata ( Fig. 3A, B View Figure 3 ). The posterior margin is straight or slightly concave. The crista cranii and the anterior process are morphologically similar to those of lacertids, even though the latter is larger (in lateral view) and distally pointed. However, the frontal of Ab. kitaibelii and Tr. aurata lacks the anterior process and the former species also has poorly developed cristae cranii ( Figs 2S View Figure 2 , 3A, I View Figure 3 ). The ventral surface is smooth, whereas a weak ( Chalcides chalcides and Chalcides striatus ; Fig. 2V View Figure 2 ) or well developed ( Chalcides ocellatus ; Fig. 2T View Figure 2 ) cover of dermal ornamentation is present in the middle of the dorsal surface. The ornamentation is lacking by the anterior and posterior ends and along the lateral margin. No sulci are visible on the ornamentation. In this case Tr. aurata is also an exception, because it has a moderately developed ornamentation that reaches the posterior margin ( Fig. 3A View Figure 3 ). Moreover, the grooves separating frontal, frontoparietal and interfrontal shields are visible in this species. The two frontoparietal shields contact each other medially, separating the frontal and interfrontal ones ( Fig. 3A View Figure 3 ). The ornamentation is usually totally absent in smaller specimens, and in Ab. kitaibelii and Ophiomorus punctatissimus (except for some weak grooves visible in some specimens of the former and in all specimens of the latter). Maximum lengths of the frontal in European species of scincids are summarized in the Supporting Information 4.