Chamaeleonidae 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

Chamaeleonidae indet.

Fig. 11C-M

Material.

Two right maxillae HLMD-Ez 1961-1962, two left dentaries HLMD-Ez 1963-1964.

Description.

Maxilla: The specimen HLMD-Ez 1961 (Fig. 11C-E ) represents the anterior maxillary section. It bears five small teeth. The fragment is relatively massively built with a slight medial curvature at its anterior end. The bone rises dorsally, but only the base of the facial process is preserved. In medial view, the anterior internal dorsal margin has a rough surface. It can be most likely interpreted as a facet for the premaxilla. The supradental shelf is thin in medial view. However, this structure is well-expanded medially, being broad in ventral view. The external surface of the preserved section of the bone is smooth. The specimen HLMD-Ez 1962 (Fig. 11F, G ) represents a posterior maxillary section - a part of the posteroventral process. It bears four teeth. In medial view, the supradental shelf is well-developed. Dorsally from this structure, the maxilla forms a longitudinal depression; a facet for the jugal is present here. The lateral surface of this fragment is smooth.

Dentary: Both dentaries are fragmentarily preserved. The specimen HLMD-Ez 1963 (Fig. 11H-J ) represents the anterior portion of the left dentary. The anterior end of the dentary is curved medially, and a large elliptical symphysis is located here. This dentary fragment bears six teeth, although it should be noted that the anterior tooth is broken off. Ventrally to it, the dental groove is present, being shallow rather than deep. The well-developed and straight supra-alveolar ridge floors it. Most of the ventral portion of the Meckel`s groove is damaged. The external surface is pierced by a labial foramen located closed to the ventral margin. The specimen HLMD-Ez 1964 (Fig. 11K-M ) bears only two teeth. Its lateral surface shows well-developed triangular interdental grooves (two are preserved), which incline anteroventrally.

Dentition: The tooth implantation is acrodont. Tooth size increases more-or-less posteriorly, but the dentary specimen HLMD-Ez 1964 and maxillary specimen HLMD-Ez 1962 show that at least the last posterior tooth is smaller than the adjacent anterior (probably penultimate) one. The teeth are triangular, with a low degree of tricuspidity - the central cusp is distinctly dominant. The teeth are compressed mediolaterally. The sizes of the inter-dental gaps are small in the anterior region and distinctly widen posteriorly. The large posterior teeth have wide interdental gaps. Thus, their bases are not in contact. On the posterior region of the maxilla, however, the size of the inter-dental gap between the last and the penultimate tooth is small.

Remarks.

The absence of pleurodont dentition in the anterior section of the tooth row allows the allocation to Chamaeleonidae without doubts ( Čerňanský 2010b; Čerňanský et al. 2020a). In contrast to chamaeleonids, agamids retain a trace of the primitive pleurodont condition in the anterior region (often in caniniform anterior teeth; Moody 1978).

Figures

Figure 11. Chamaeleo andrusovi (A, B) and Chamaeleonidae indet. (C-M) from the Echzell locality. Frontal HLMD-Ez 1960 in (A) dorsal and (B) ventral views. Right maxilla HLMD-Ez 1961 in (C) lateral, (D) medial and (E) ventral views. Right maxilla HLMD-Ez 1962 in (F) lateral, and (G) medial views. Left dentary HLMD-Ez 1963 in (H) lateral, (I) medial, and (J) dorsal views. Left dentary HLMD-Ez 1964 in (K) lateral, (L) medial, and (M) dorsal views.