Chalcides Chalcides sp.

Vasilyan, Davit, Cernansky, Andrej, Szyndlar, Zbigniew & Moers, Thomas, 2022, Amphibian and reptilian fauna from the early Miocene of Echzell, Germany, Fossil Record 25 (1), pp. 99-145 : 99

cf. Chalcides Chalcides sp.

Fig. 12C-H

Material.

Right maxilla HLMD-Ez 1990, six right dentaries HLMD-Ez 1993-1998, one left dentary HLMD-Ez 1999.

Description.

Maxilla: One fragment of a right maxilla is preserved. The specimen HLMD-Ez 1990 (Fig. 12C, D ) represents the posterior region of the maxilla. The lateral surface of this specimen is completely smooth. This maxillary fragment bears eight tooth positions with five teeth still attached). The nasal process is partly preserved. Note, however, that the dorsoventral height of the posteriorly located posteroventral process of the maxilla is still significant. Thus, it forms the wall along the entire length of the process here rather than narrowing posteriorly into a tip. Moreover, the shallow notch is developed posteriorly between the dental crest supporting teeth and the dorsally located wall. Although the posterior portion of this dorsal wall is broken off, it can be estimated that, when completely preserved, it exceeds the dental part posteriorly. The dorsal margin of the posteroventral process is slightly damaged, but this portion has a thicker appearance than the ventrally located region possessing a longitudinal depression. This depression partly forms a jugal facet. The ventrally located supradental shelf is thin and expands laterally. It is dorsally convex, but only a small portion is completely preserved. No alveolar superior foramen is preserved here. This highlights a possible anterior position of this foramen.

Dentary: The description is based on several fragments (Fig. 12E-H ), most of which represent more-or-less anterior sections. The most complete specimen bears 20 tooth positions; however, its posterior region is broken off. The real tooth number is undoubtedly slightly higher. The dentary is slender, anteroposteriorly elongated. The bone gradually narrows anteriorly. In dorsal view, its anterior portion has a small medial curvature. The otherwise smooth lateral surface is pierced by several labial foramina located in the mid-portion of the bone. In medial view, the Meckel`s groove is narrow, but entirely open. The subdental shelf is medially protruded and robust, especially in the anterior region. It narrows posteriorly because of the presence of the splenial articulation facet. The symphysis is small, rectangular and somewhat narrow.

Dentition: The tooth implantation is pleurodont. The teeth are conical and high. They are closely spaced with small interdental gaps. The tooth crowns are mediolaterally compressed. Thus, the necks have a slightly lingually enlarged appearance. The tooth crowns have blunt apices. In medial view, they have a labial and lingual cusp. The lingual side, bordered by the culmen lateralis posterior and anterior, has striation formed by apicobasal ridges. They are more-or-less parallel to each other and their number usually varies from around five to eight. The labial aspect of the teeth appears smooth. Resorption pits pierce the tooth bases of some teeth.

Remarks.

All scincid elements here are assigned to one species based on the significant similarity in the dentition. Moreover, all elements are from the same locality and comparable in size. Besides tooth morphology (see Kosma 2004), the Echzell skink material can be allocated to the clade Scincidae (sensu Hedges 2014; Scincinae sensu Estes et al. 1988) based on the narrow but fully open Meckelian groove in the dentary. This is present in members of the Scincidae clade and in, e.g., Ateuchosaurus , whereas it is closed in members of Acontiidae , Sphenomorphidae , Eugongylidae , Lygosomidae , Egerniidae and Mabuyidae (see, e.g., Greer 1970, 1974; Evans 2008; Hutchinson and Scanlon 2009; Čerňanský et al. 2020b; Čerňanský and Syromyatnikova 2021).

The specimens resemble members of the genus Chalcides . The Miocene species of this taxon is represented by Chalcides augei (see Čerňanský et al. 2020b) and the Echzell material shows similarities to this taxon. Note that usually five striations are reported in Ch. augei , it can range from five to seven, and the small variation in the number of striae (from five to seven ot eight) can be seen in specimens from Austria as well ( Čerňanský 2016). However, the limitation of the Echzell material does not allow alpha taxonomy and caution is needed here.

Figures

Figure 12. Lacertidae indet. (A, B) and cf. Chalcides sp. (C-H) from the Echzell locality. Right dentary HLMD-Ez 1992 in (A) lateral and (B) medial views with a detail of dentition. Right maxilla HLMD-Ez 1990 in (C) lateral and (D) medial views with a detail of dentition. Right dentary HLMD-Ez 1994 in (E) lateral and (F) medial views with a detail of dentition. Right dentary HLMD-Ez 1993 in (G) lateral, and (H) medial views.