Cordylidae, Gray, 1837

Čerňanský, Andrej, 2012, The oldest known European Neogene girdled lizard fauna (Squamata, Cordylidae), with comments on Early Miocene immigration of African taxa, Geodiversitas 34 (4), pp. 837-848 : 843-844

? Cordylidae indet. ( Fig. 6 )

LOCALITY AND HORIZON. — Merkur-North opencast mine; Lower Miocene (Eggenburgian), Lower Orleanium, zone MN 3a.

MATERIAL EXAMINED. — Left maxilla (Ah-939 SGDB).

DESCRIPTION

Maxilla

The maxilla is robust and subtriangular in shape ( Fig.6 ). Unfortunately, it is not completely preserved. Its posterior end is broken and the majority of the anterior portion is also missing. The external surface of the nasal process, above the row of seven labial foramina (foramina pro rami nervorum alveolarium superiorum), is ornamented by pits and very short irregular grooves. Unfortunately, the dorsal-most portion of the nasal process and the whole premaxillary process is broken. The dorsal section of the posterior portion behind the nasal process is short, well bounded from the dental portion (pars dentalis) of the maxilla – the distal end of the nasal process is stepped, forming a posteriorly oriented triangular tip. The region below the labial foramina is smooth. The inner surface bears a prominent well-developed straight supradental shelf which supports the tooth bases along the entire tooth row. There are 12 preserved teeth. The shelf distinctly widens medially approximately between the second and last third of its length. Here, a large infraorbital foramen is situated at the level of the 3 rd posterior tooth counted from the back.A deep and broad depression extends from this foramen to the posterior end of the maxilla and forms the articulation for the jugal. Although the sulcus dentalis is well-developed, unfortunately it is impossible to demonstrate its continuation since this part is mostly unpreserved on the material.

Dentition

The dentition is pleurodont. The teeth are high, robust and slightly curved lingually. The tooth shafts are tall with their bases slightly expanded lingually and oval in cross-section. Huge circular resorption pits are present on the lingual sides of some maxillary tooth bases. The teeth are closely distributed with inter-dental gap sizes very small or even absent between some maxillary teeth. The apical parts of the teeth are variable exibiting heterodont dentition. The anteriorly situated teeth are larger and considerably more pointed. They are slightly posteriorly oriented with the crowns bent posteromedially. The teeth of the posterior section of the tooth row are lower and blunter, being close to each other, and of irregular size. They are slightly bicuspid with a main cusp and an anteriorly situated lateral cusp. The labial surfaces of the tooth crowns are slightly convex with weak radial striations. A pronounced pattern of striations has developed on the lingual surface of the tooth crown between the culmen lateralis anterior and culmen lateralis posterior (terms after Richter 1994). The number of striae on the lingual side is variable, but mostly around 10-11 and (14 in the last tooth). The angle between the crista mesialis and the crista distalis of the posterior teeth measures around 110 degrees. As a result of this apical angle, the occlusal cutting edges are generally relatively sharp.

REMARKS

The attribution of the maxilla to Scincoidea is beyond doubt. However within the superfamily Scincoidea , Scincidae and Cordylidae are often difficult to distinguish ( Gao & Fox 1996). The exact identity of the maxilla Ah-939 SGDB from Merkur-North is also rather uncertain. The tooth morphology present here and the combination of the distinctive sulcus dentalis, wide posterior portion, the robust shape and the presence of dermal sculpturing are more common among the cordylids than the scincids. Unfortunately, the isolated maxilla lacks enough diagnostic features to support this, thus enabling determination to the family level somewhat questionable.

The number of striae on the lingual surface of the crowns is similar to that of the material described from Puttenhausen B by Böhme (2010), where the number reaches 12. It also possesses similar characteristics to heterodont dentition. However, the morphology of the tooth crowns is different – all teeth are unicuspid and distinctly blunter in the material from Puttenhausen B (after Böhme 2010), where the striae are mostly indistinct. In the material from the locality of Petersbuch 2, described by Kosma (2004) as Bavaricordylus ornatus , the cristae form the blunt apical portion with an apical angle of about 150 degrees. There, approximatelly 20 striae are present. The morphology of the tooth crowns in the maxilla described herein is certainly closer to that of Palaeocordylus Roček, 1984 , especially in the anteriorly situated teeth which are very similar to that on the premaxilla of P. bohemicus from Dolnice (DP FNSP 114; in Roček 1984: pl. III, figs 3; 5). In P. bohemicus , the infraorbital foramen is situated at the level of the 5th tooth position from the back, while it lays at the level of the 3rd one in the material described here.

Figures

FIG. 6.—? Cordylidae indet.;the left maxilla Ah-939 SGDB:A, labial view; B, C, D, lingual views with the details of the tooth crowns. Scale bars: A, B, 2.5 mm; C, 1 mm; D, 500 µm.