Varanidae Gray, 1827

Varanidae Gray, 1827 View in CoL View at ENA (sensu Estes et al., 1988)

cf. Varanidae indet.

Figure 46 View Fig

Material. Spilia 4: one isolated tooth ( UU SP4 506).

Description. Tis isolated tooth from Spilia 4 misses its proximal part ( Fig. 46 View Fig ). Te preserved portion is 3.1 mm in length. Te tooth is strongly labiolingually compressed, slightly curved posteriorly, canine-like and pointed. It is smooth, without longitudinal grooves. Te mesial and distal cutting edges are slightly serrated, with the distal one being more serrated than the mesial one.

Remarks. Te single and partial tooth from Spilia 4 is tentatively attributed to an indeterminate monitor lizard because of the overall similarity between it and the general morphology of varanid teeth: labiolingual compression that encompasses the pulp cavity, presence of serrated carinae, posterior bending (Bhullar & Smith, 2008; Bullet, 1942; Georgalis et al., 2023b; Ivanov et al., 2018; Peyer, 1929; Villa et al., 2018). Nevertheless, the attribution cannot be confidently confirmed because of the missing tooth base, the absence of which hinders the recognition of the main apomorphy of varanoid teeth (namely, the presence of plicidentine; Estes et al., 1988; Georgalis & Scheyer, 2019; Kearney & Rieppel, 2006). Remarkable is also the absence of grooves in the preserved portion of the basal area of the tooth; such grooves are generally associated with the presence of the plicidentine (see for example Villa et al., 2021, fig. 17a–d). Nevertheless, the labiolingual tooth crown compression, with mesial and distal carinae is considered a synapomorphy of the varanoid genera Lanthanotus Steindachner, 1878 , and Varanus , with the latter genus having this compression extending to the tooth base and being visible in the pulp cavity (Bhullar & Smith, 2008; Georgalis et al., 2023b). Most of the tooth base is not preserved in the Spilia tooth, but nevertheless it seems that the pulp cavity is compressed, a feature typical of Varanus (Georgalis et al., 2023b) .

(non-snake) Squamata indet.

Figure 47 View Fig

Material. Chalicorrema: one fragment of indeterminate tooth bearing bone ( UU RA 405); Spilia 3: one cervical vertebra ( UU SP3 615); Spilia 4: three quadrates ( UU SP4 608, UU SP4 612, and UU SP4 613), one indeterminate cranial element ( UU SP4 692), one axis ( UU SP4 626), three trunk vertebrae ( UU SP4 642, UU SP4 644, and UU SP4 710), two sacral vertebrae ( UU SP4 703,

708), three caudal vertebrae ( UU SP4 621, UU SP4 628, and UU SP4 656), five ribs ( UU SP4 505), two humeri ( UU SP4 607 and UU SP4 610), and five femora ( UU SP4 609, UU SP4 651, UU SP4 652, and UU SP4 702).

Description and remarks.

Te fossil remains from Spilia 3 and Spilia 4 pertain to lizards, but they cannot be confidently identified because of either an overall poor preservation or the current lack of data on the comparative postcranial osteology of these reptiles.

Te three quadrate fragments from Spilia 4 ( UU SP4 608, UU SP4 612, and UU SP4 613) only preserve the pillar, which is narrow and straight and expands dorsally and ventrally ( Fig. 47c–k View Fig ). In all three specimens, a low medial lamina is present but the lateral lamina is broken off .

Te humerus (UU SP4 610) from Spilia 4 ( Fig. 47m View Fig ), as well as most femora, are very small, but well ossified. Tey could thus pertain to the small-sized lacertid identified based on the above-described coronoid UU SP4 704. Te other humerus (UU SP4 607) is also very small, but its epiphyses are not ossified, thus suggesting it belonged to a juvenile. At least one rather large femur (part of UU SP4 702) is also present, possibly attributable to the medium-sized lacertid.

Te trunk vertebrae from Spilia 4 are small, with a centrum length ranging from 1.8 to 1.9 mm. Tey are poorly elongated and have a not compressed centrum. Tis morphology is more similar to the one of lacertid vertebrae, among non-snakes squamates from Spilia. Pending a real detailed comparative analysis of the vertebrae of these squamates, however, this possible identification should just remain tentative.

It is also worth noticing the specimen UU SP4 656

( Fig. 47l View Fig ). Tis is a medium-sized caudal vertebra, with a not compressed, procoelous centrum. Te centrum length is about 3.5 mm and both cotyle and condyle are circular. Tere is no precondylar constriction. Te ventral surface of the centrum is distinctly keeled and posteriorly it displays two small articular surfaces for the chevron bone located immediately anterior to the posterior condyle. Te left transverse process is better preserved than the right one, even though the distal half is still missing. Te autotomy plane is not visible. Te neural arch is poorly preserved. A laminar neural spine is present, but broken. Te suboval left prezygapophysis is preserved, with a slight dorsal inclination in anterior view. On the lateral surface of the neural arch, a very low but distinct postzygoprezygapophyseal lamina is visible. Tis morphology fits well with caudals of lacertids, thus suggesting that this vertebra could pertain to the medium-sized one (cf. Lacerta sp. ) identified in Spilia based on cranial bones. UU SP4 621 and UU SP4 628 are smaller (centrum length around 3 mm and 2.5 mm respectively) and less preserved, but the morphology is more or less the same. Tey could pertain to indeterminate lacertids as well.

As for the single element from Chalicorrema, this specimen (UU RA 405) is a fragment of tooth bearing bone

( Fig. 47a, b View Fig ). It is either part of a maxilla or a dentary, but this cannot be clearly stated. It carries seven tooth positions, two of which are still occupied by moderately preserved teeth. Te teeth are pleurodont, cylindrical, slender and closely spaced. Te tooth base is not swollen. Both teeth have a poorly preserved crown, thus hindering a clear recognition of the morphology. Te crown of the (probably) most anterior tooth appears rounded, but this is due to breakage and wearing. Te other tooth seems to display a small anterior cusp mesially, but, at a closer inspection, this comes out as an artifact due to breakage. Te fragment is 4.0 mm long. According to this description, it is obvious that a third lizard taxon, a small lizard with a pleurodont dentition, is also present in the Chalicorrema fossil assemblage, but its taxonomy cannot be confidently stated based on this single and very poorly preserved specimen. Considering what is preserved of its tooth morphology and the fossil record of non-snake squamates in the Neogene of Europe, teeth of this element appear more similar to those of lacertid and scincoid lizards, and maybe to a lesser degree, gekkotans. However, a clear attribution is not possible for the moment, and we only refer this fossil to an indeterminate lizard, different from the above-described agamine and anguine from that locality.