Anguinae indet.

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

Anguinae indet.

Fig. 15

Material.

One right maxilla HLMD-Ez 1966, one right and one left dentaries HLMD-Ez 1967-1968, 12 dorsal vertebrae HLMD-Ez 1969-1980.

Description.

Maxilla: Only a fragment of the right maxilla is preserved (Fig. 15A, B ). It represents the area around the superior alveolar foramen plus the section of the posteroventral process. This maxillary fragment bears eight tooth positions (one tooth is still attached). The otherwise smooth lateral surface is pierced by the labial foramina - three and a half are preserved. The medial side bears the well-developed supradental shelf. At the level of the fifth tooth position (counted from posterior), the shelf expands medially to form the palatine articulation. At this level, the superior alveolar foramen is located on the dorsal side of the shelf. Only the base of the nasal process is preserved; the rest of the bone is broken off. The posterior portion gradually narrows into the posteroventral process. Its dorsal margin smoothly decreases ventrally without being stepped.

Dentary: Two dentary fragments are preserved, both representing only the posterior portions (Fig. 15C-F ). The right one (HLMD-Ez 1967) possesses five tooth positions, where the penultimate and fourth (counted from posterior) are still partly preserved. Except for two labial foramina, the lateral surface is smooth (only one foramen is preserved in HLMD-Ez 1968). The medial surface exhibits open Meckel`s groove, which narrows anteriorly. It is roofed by the concave, shallow subdental shelf. The position of the anterior inferior alveolar foramen between the dentary and a splenial can be recognized at the level of the fifth tooth position, but this area appears to be eroded. The alveolar foramen is located at the level of the third tooth position. The intramandibular septum, which separates the alveolar canal from Meckel`s groove, is completely fused with the body of the dentary (the free ventral portion is absent). The surangular spine is damaged, so only its root portion can be recognized. The angular process is broken off. The other posterior processes are damaged. The left dentary HLMD-Ez 1968 represents a specimen with four tooth positions - only one complete tooth and the base of another one are still preserved. The position of the anterior inferior alveolar foramen can be still recognized on the subdental shelf. The splenial spine is absent in both specimens. Due to poor preservation of this area, however, this appears to represent a postmortal damage only.

Dentition: The tooth implantation is shallowly pleurodont. The teeth are large, well exposed over the dorsal crest, which supports them laterally. They are conical and distinctly recurved. Their tips are pointed. The mesial and distal cutting edges are well developed. The tooth bases are broad, being pierced by resorption pits. In most cases, the pits are located slightly posterior to the tooth axis. The dentary teeth are smooth by weathering (or affected by digestive process of carnivores), the maxillary tooth crown possesses fine but dense striations on both labial and lingual sides.

Dorsal vertebra: The description is based on the well-preserved specimen HLMD-Ez 1969 (Fig. 15G-J ). The vertebral centrum is anteroposteriorly elongated. The height of the vertebra gradually increases posteriorly. The neural spine is low, however, its dorsal portion is broken off. It forms a ridge running along almost the entire length of the dorsal section of the neural arch. In dorsal view, the ridge is thin, becoming less distinct in the anterior section. In the posterior third of its length, it is well defined and widens at its posterior end. The neural canal is high and well arched dorsally. The cotyle is depressed, being mediolaterally expanded and broader than the neural canal. However, the maximum height of the cotyle is lower than the maximum dorsoventral height of the neural canal. The pre- and postzygapophyses are well expanded laterally; a well-developed interzygapophyseal constriction is located between them. The pre- and postzygapophyses have elliptical articulation surfaces, oriented more or less anteroposteriorly. The prezygapophyses are inclined from the horizontal plane at an angle of approximately 30°. The synapophyses are protruding laterally, being square in shape. The condyle, which is well-protruded posteriorly, is markedly depressed as well as the above-mentioned cotyle. The ventral surface of the centrum is flat. It is pierced by two subcentral foramina in the anterior one-third of the centrum. The lateral margins of the centrum have a concave course, running more anterolaterally from the level of the subcentral foramina.

Remarks.

Among extant anguine genera, the morphology of herein described vertebrae resembles that of Ophisaurus ( Čerňanský et al. 2019). The maxilla with markedly recurved teeth and vertebrae similar to those from Echzell have been described also from Gratkorn (see Böhme and Vasilyan 2014). Such a distinct tooth curvature is not very typical among members of extant Ophisaurus (see Klembara et al. 2014), but can be found in fossil species, e.g. in O. acuminatus (see Klembara and Čerňanský 2020). However, it should be noted that some features in the dentary, such as the presence of a splenial spine, cannot be supported with confidence due to poor preservation. Moreover, another crucial reason exists why the allocation of this material to Ophisaurus might be problematic - the occurrence of a new taxon Smithosaurus echzellensis in both Echzell and Gratkorn localities. We cannot entirely exclude the very plausible option that some of those specimens (if not all) belong to this newly described taxon. For this reason, we allocated this material only as Anguinae indet. Caution is also needed in regards to interpretations of isolated jaw fragments and isolated vertebrae from other European Miocene localities, where such incomplete and fragmentary materials are often described as Ophisaurus . More complete and articulated material of Smithosaurus echzellensis , in which bones can be associated together to observe the anatomy of this taxon, is crucial to resolve this problem.

Figures

Figure 15. Anguinae indet. from the Echzell locality. Right maxilla HLMD-Ez 1966 in (A) lateral, and (B) medial views. Right dentary HLMD-Ez 1967 in (C) lateral, (D) medial and (E) dorsal views. Left dentary HLMD-Ez 1968 in (F) medial view. Dorsal vertebra HLMD-Ez 1969 in (G) anterior, (H) posterior, (I) dorsal and (J) ventral views.