Cadurcogekko cf. piveteaui, Hoffstetter, 1946

Georgalis, Georgios L., Čerňanský, Andrej & Klembara, Jozef, 2021, Osteological atlas of new lizards from the Phosphorites du Quercy (France), based on historical, forgotten, fossil material, Geodiversitas 43 (9), pp. 219-293 : 223-227

Cadurcogekko cf. piveteaui

( Figs 2-4 )

REFERRED SPECIMENS. — A frontal (NHMW 2019/0052/0002); a left maxilla (NHMW 2019/0052/0001).

DESCRIPTION

Frontal NHMW 2019/0052/0002 ( Fig. 2 )

The left and right frontals are fused in this specimen, forming a single element, with a length of 8.1 mm ( Fig. 2 ). It is almost completely preserved and only its anterior portion is damaged. It is rectangular, with a slight mid-constriction. Thus, the lateral margins are rather concave in dorsal aspect and fluently continue into well laterally expanded posterolateral processes. These processes form narrow triangles with pointed lateral terminations. The anterolateral margins of both processes are stepped due to a presence of short and narrow facets for the postfrontal. An additional step is present on both sides in the anterior region of the lateral margin of the frontal. There, the large facet for prefrontal is located ( Fig. 2B, C ). It is mainly exposed in ventral aspect as a rough surface. It is wedge-shaped posteriorly, where its peak reaches posterior to the level of the step. The facet for prefrontal and postfrontal are not in contact, thus the frontal is not fully excluded from the orbit. In ventral view, the frontal cranial crests run medially from the posteroventral processes and merge together further anteriorly ( Fig. 2B ). They are completely fused to form a tunnel-like structure. The overall dorsal surface of the frontal, although slightly bulged in the central region, is slightly depressed, with dorsally inclined lateral portions. This external surface is sculptured, having a wrinkled appearance. The sculpturing pattern consists of ridges and pits ( Fig. 2A ). They are mainly developed in the mid-section and run to the periphery of the surface. A deep depression runs along the entire dorsal surface of both posterolateral processes. The posterior margin of the frontal is almost straight.

Maxilla NHMW 2019/0052/0001 ( Figs 3 ; 4 )

NHMW 2019/0052/0001 represents an almost complete left maxilla ( Figs 3 ; 4 ). This element is elongate and lightly built, measuring 14.2 mm in length. It is straight with a small medial anterior curvature. A complete tooth row is preserved, bearing 37 tooth positions, of which six complete teeth are still attached. The premaxillary process is bifurcated. The external ramus of this process is short and blunt, whereas the internal ramus is more distinct and broader. The internal ramus is more medially oriented and more dorsally located relative to the external one. Between them, an oval and wide premaxillary notch is present. Dorsal to it, an anterior opening for the superior alveolar canal is located. The supradental shelf is thin. Its portion located in the anterior two thirds is slightly bent dorsally (convex) and expanded medially. In dorsal view, the medial margin of the supradental shelf is rounded, reaching the maximum of expansion at the level around of 18th tooth position (counted from anterior). This forms a palatine process. Slightly posteriorly to it, the rounded but flat superior alveolar foramen is located at the dorsal portion, at the level of the 21 st tooth position (counted from anterior). The posterior 1/3 of the supradental shelf is more or less straight in medial aspect. In posterior direction, it is gradually less expanded medially. The anteroposterior length of the nasal process is greater than its dorsal height. The dorsal margin of the nasal process appears to be slightly worn, but in the case that it represents more or less the original shape, it shows a lack of a pronounced dorsal process. This configuration of the nasal process contrasts sharply with the prominent, often pointed process typical of many gekkotans and resembles that seen in Euleptes Fitzinger, 1843 (e.g., Bauer et al. 1997; Čerňanský et al. 2018; Villa et al. 2018). The nasal process is trapezoidal in shape, with the posterior margin being more ventrally slopped relative to the anterior one. The anterior margin possesses a free terminus. It forms a triangular tip (this feature can be seen in extant and extinct species of the genus Euleptes but also in the genera Hemidactylus Goldfuss, 1820 , and Tarentola Gray, 1825 ; see e.g., Čerňanský et al. 2018; Villa et al. 2018), well delimited from the dental portion of the maxilla. In the anterior region of the nasal process, on the medial side there is a fine ridge that runs posterodorsally. This ridge originates from the supradental shelf at the level of the fifth tooth position. The internal side of the nasal process posterior to this ridge is excavated, forming a cavity. In dorsal aspect, the process has a rounded, laterally convex appearance.

The posteroventral process of maxilla is moderately long. It possesses a longitudinal deep groove, which is roofed by a bent, dorsally depressed bony flange. This flange continues here from the dorsolateral side of the posteroventral process.

The lateral surface of maxilla is pierced by nine labial foramina located in the ventral series, where the posteriormost one is located at the level of the 27th tooth position ( Figs 3A ; 4A ). Posteriorly from this foramen, a well-developed groove runs along the entire portion of the posteroventral process. Dorsal to this series, the surface is pieced by additional five, irregularly arranged foramina. The rest of the lateral surface is rather rugose and irregularly pitted.

REMARKS

The material can be referred to Gekkota on the basis of the following characters: 1) absence of osteoderms fused to the skull bones; 2) unpaired frontals; 3) fused subolfactory processes of frontal in the mid-line to form a tunnel like structure; and 4) the high number of conical, unicuspid pleurodont teeth ( Estes 1983; Daza et al. 2014). The maxilla can be referred to the genus Cadurcogekko on the basis of the presence of rugose surface of the nasal process, an elongated groove associated with the most posterior neurovascular foramen, and a postnarial anterodorsal depression of the element ( Augé 2005).

The genus Cadurcogekko is known exclusively from localities within the Phosphorites du Quercy.Two species of this genus are currently regarded as valid: the type species, Cadurcogekko piveteaui from the old collections of the Phosphorites du Quercy, and Cadurcogekko verus Bolet, Daza, Augé & Bauer, 2015 , from the late Eocene (MP 17) of Les Pradigues, Quercy (see Bolet et al. 2015). Notably, the holotype dentary of the type species, C. piveteaui , was originally described as a frog by Piveteau (1927), until it was eventually demonstrated by Hoffstetter (1946) that it pertained instead to gekkotans. The two valid species of Cadurcogekko can be distinguished by: 1) different size of the available elements, with Cadurcogekko verus being smaller than C. piveteaui ; 2) lower maxillary tooth number – according to Bolet et al. (2015), C. verus possesses 30 vs. 50 in C. piveteaui . The tooth row in the referred maxilla MNHN.F.QU17734 of Cadurcogekko piveteaui from the late Eocene (MP 17) of Perrière, Quercy, is incomplete, lacking its posterior portion; it has 38 tooth positions ( Augé 2005: fig. 59). Daza et al. (2014) estimated the tooth number in a complete tooth row to be between 40 and 44, contrasting with only 27 tooth positions in C. verus ; and 3) a coarser sculpture on the external surface of the maxilla and possibly the frontal in C. verus .

Note that a third named species of the genus, Cadurcogekko rugosus Augé, 2005 , has recently been reidentified as a scincid and placed accordingly in its own genus, Gekkomimus Bolet, Daza, Augé & Bauer, 2015 , by Bolet et al. (2015). Nevertheless, the figure of the type material of Cadurcogekko verus in Bolet et al. (2015: fig. 1) deserves a comment at this point. Bolet et al. (2015) established the species Cadurcogekko verus and they supposedly figured its holotype, the right maxilla UM PRA 9, in their fig. 1. That specimen, UM PRA 9, originated from the late Eocene (MP 17) of Les Pradigues, Quercy and was previously allocated to C. rugosus by Augé (2005). However, despite their figure caption which stated that UM PRA 9 was figured there, Bolet et al. (2015) did not figure at all this holotype, but instead their fig. 1 represents another specimen, the right maxilla MNHN.F.QU17734 of C. piveteaui originating from the late Eocene (MP 17) of Perrière, Quercy (see Augé 2005: fig. 59a-b [for MNHN.F.QU17734] vs. 64a-b [for UM PRA 9] and Daza et al. 2014: fig. 5a-b [for MNHN.F.QU17734]; this paper: Fig. 5 [for UM PRA 9]). In addition, Daza et al. (2014) mentioned in their text the maxilla UM PRA 9 (following the previously suggested referral by Augé [2005] to C. rugosus ) and stated that they figured this specimen in their figure 5j-k. However, the photographs of the maxilla “UM PRA 9” figured by Daza et al. (2014: fig. 5j-k) represent a different specimen from the drawings of the maxilla “UM PRA 9” figured by Augé (2005: fig. 64a-b). Judging from newly furnished photographs of the specimen provided to us by UM, we here confirm that UM PRA 9 is the specimen figured by Augé (2005: fig. 64a-b) and not the one figured by Daza et al. (2014: fig. 5j-k). All these being said, despite the erroneous figure of Bolet et al. (2015), UM PRA 9 indeed represents the holotype of Cadurcogekko verus , as the diagnosis and description of this species is based on this specimen. We here provide photographs of this specimen, UM PRA 9, for the first time ( Fig. 5 ).

The left maxilla NHMW 2019/0052/0001 described herein exhibits a complete tooth row, possessing 37 tooth positions. This seems to be an intermediate condition between Cadurcogekko verus and that what has been previously estimated for Cadurcogekko piveteaui . This brings several questions about this character state in these two currently valid species. The frontal NHMW 2019/0052/0002 is almost identical with specimen MNHN.F.QU17165, which has been referred to C. piveteaui (see Augé 2005: fig. 60; Daza et al. 2014: fig. 5h-i). However, the sculpturing pattern present on the dorsal surface of NHMW 2019/0052/0002 appears to be slightly more strongly developed relative to that of MNHN.F.QU17165. The frontal NHMW 2019/0052/0002, despite the fact that its anterior portion is damaged, currently represents the best preserved frontal of Cadurcogekko . In any case, the overall morphologies of the specimens NHMW 2019/0052/0001 and NHMW 2019/0052/0002 fit better to the diagnosis previously stated for C. piveteaui , although with some doubts. Therefore, we have decided to refer this gekkotan material to as Cadurcogekko cf. piveteaui .

Figures

FIG. 2. — Cadurcogekko cf. piveteaui. Photographs of frontal NHMW 2019/0052/0002 in dorsal (A), ventral (B), left lateral (C), and anterior (D) views.Scale bar:2 mm.

FIG. 3. — Cadurcogekko cf.piveteaui. Photographs of left maxilla NHMW 2019/0052/0001 in lateral (A), medial (B),dorsal (C), and ventral (D) views.Scale bar:2 mm.

FIG. 4. — Cadurcogekko cf. piveteaui. Virtual 3D models of left maxilla NHMW 2019/0052/0001 in lateral (A), medial (B), dorsal (C), and ventral (D) views. Note that further preparation on this specimen was conducted after the micro-CT scanning. Scale bar: 2 mm.

FIG. 5. — Cadurcogekko verus Bolet, Daza, Augé & Bauer, 2015. Photographs of the holotype right maxilla UM PRA 9 in lateral (A) and medial (B) views. Scale bar: 2 mm.