Lacerta sp.

Čerňanský, Andrej, 2024, The first lacertid and partly articulated snake from the Middle Miocene of the Devínska Kobyla Hill in Slovakia, from the type locality of the earliest known seal, Comptes Rendus Palevol 23 (24), pp. 385-399 : 388-390

cf. Lacerta sp.

( Fig. 1)

MATERIAL EXAMINED. — Slovakia • Bratislava, Devínska Nová Ves, Bonanza site ; Middle Miocene (MN 6b); SNM Z 29221 , left maxilla .

LOCALITY AND HORIZON. — Slovakia, Bratislava, Devínska Nová Ves, Bonanza site; Middle Miocene ( MN 6b).

DESCRIPTION

Maxilla

The left maxilla is fairly well preserved although incomplete – most of the specimen is an imprint of its lateral side in the sediment ( Fig. 1). There is a subvertical crack running along the mid-portion of the element. The bone is partly preserved in the anterior and posterior region (some remains also occur in the central region of the facial process). The maximum anteroposterior length of the preserved portion is 10 mm and its maximum dorsoventral height is 5.6 mm. It bears 17 tooth positions (four and half teeth are still attached in the anterior section and remains of five teeth are partly preserved in the posterior section). The tooth row is almost complete and thus it can be estimated that the complete maxilla possessed around 18-19 teeth. The premaxillary process of the maxilla is damaged and covered by matrix. The CT scan reveals that part of the external ramus of the premaxillary process is still preserved as a narrow expansion. The lateral face of the maxilla above the teeth is pierced by relatively large supralabial foramina arranged in a single line (five are preserved as imprints). The supradental shelf (sensu Rage & Augé 2010) is damaged, with small portions partly visible in the posterior and anterior sections. At the end of the anterior section, the anterior border of the cavum nasi can be recognized. It forms a slightly medially bulged ridge. Here, the anterior margin of the facial process rises upwards to form the posterior margin of the external naris. However, only the ventral portion of this region is preserved – the facial process is mostly preserved only as an imprint of its lateral surface. Based on this imprint, the facial process clearly possessed three attached osteodermal shields based on positive imprints of sulci. The sculpture (sensu Glynne et al. 2020) of these osteoderms is well developed and strong. It consists of densely spaced grooves and ridges (connected in some places). Most of these surface features are directed posterodorsally but there is an exception anteriorly where the orientation is rather irregular (roughly radial; this might indicate an ossification centre). The nasal process is roughly trapezoidal in shape. It is tall, forming an almost perpendicular wall. Its anteroposterior width is larger than its dorsoventral height. Its dorsal margin is probably not completely preserved, because this portion is usually slightly bent medially. In any case, a part of the frontal process can be recognized in the anterior region. The triangular prefrontal process is located in the dorsal region, posterior to the frontal process. Further posteriorly, the facial process gradually decreases ventrally and fluently continues into the posteroventral process of the maxilla. The latter gradually narrows posteriorly, having a concave dorsal margin. The posterior portion is poorly preserved, but its morphology indicates that it was stepped ( Fig. 1D). The tooth row does not reach the posterior end of the bone, leaving a small posterior toothless portion.

DENTITION

The tooth implantation is pleurodont. The teeth are tall, rising above the dental crest by approximately one-third of the tooth length. In general, teeth are relativelly robust and the tooth size appears to be slightly enlarged posteriorly. The tooth crowns are lingually slightly concave. All teeth which can be observed (including their imprints in the posterior section of the tooth row) are bicuspid (perhaps except for the first anterior preserved one which seems to be monocuspid). There is a dominant distal cusp which is large and pointed. A mesially located accessory cusp is well defined. It is separated from the dominant cusp by a notch, which further continues into a distinct groove. This groove gradually diminishes dorsally. The accessory cusp has a sharp appearance. It is relatively large, reaching a half of the mesiodistal width of the dominant cusp. Thus, the whole tooth crown seems to be almost bifurcated. The accessory cups is more-or-less straight, whereas the dominant cusp is slightly curved posterolingually. For this reason, the mesial edge (the crista mesialis) of the dominant cusp is longer than its distal one. Weak striations can be recognized on the lingual side of the tooth crown. The tooth necks are slightly swollen lingually. Interdental gaps are present, the gap size in preserved anterior teeth forms approximatelly half of the mesiodistal length of the tooth shaft in the middle region.

COMMENTS

The DVN Bonanza lizard specimen SNM Z 29221 described here can be allocated to Lacertidae without doubts (see Discussion: Taxonomic allocation of the lizard). However, the material is limited, represented by an isolated and incomplete maxilla which is actually not the best elements for alpha taxonomy.