Cadurcogekko verus, Bolet, Arnau, Daza, Juan D., Augé, Marc & Bauer, Aaron M., 2015

Bolet, Arnau, Daza, Juan D., Augé, Marc & Bauer, Aaron M., 2015, New genus and species names for the Eocene lizard Cadurcogekko rugosus Augé, 2005, Zootaxa 3985 (2), pp. 265-274 : 266-268

Cadurcogekko verus sp. nov.

( Fig. 1 )

Holotype. USTL, PRA 9 (almost complete right maxilla).

Type locality. Les Pradigues (MP17), Phosphorites du Quercy, France.

Referred material. From Sindou D (MP18-19): USTL, SND 2016 (frontal); USTL, SND 626, 627 (two dorsal vertebrae, note that these specimens were reported as uncatalogued in Augé 2005).

Chronological range. From MP17 to MP19 (late Eocene). Les Pradigues (MP17) and Sindou D (MP18-19).

Etymology. Latin ‘ verus ’, meaning true, referring to the fact that this species is being described after been separated from the C. rugosus holotype, which actually corresponds to a scincid (see below).

Diagnosis. A species of Cadurcogekko differing from C. piveteaui in its smaller size, a lower tooth count on the maxilla (ca. 30 vs. 50 in C. piveteaui ), and a coarser ornamentation on the labial surface of the maxilla and possibly the frontal.

Remarks. The holotype of Cadurcogekko rugosus Augé, 2005 is clearly a scincid dentary. Because the species name is linked to the holotype, which exhibits significant differences with respect to both extant and extinct members of Scincidae , we assign this species to a new genus (see below). The fragment of left dentary (USTL, SND 625; Fig. 2 ) tentatively referred to C. rugosus by Augé (2005) presents a closed Meckelian canal, but the clearly tricuspid teeth, the way the Meckelian canal is fused, and the overall morphology of the dentary all allow a referral to the iguanid Cadurciguana hoffstetteri Augé, 1987. This taxon was previously known from Sindou D on the basis of vertebrae ( Augé 2005), and misidentification of Cadurciguana as a gekkotan has been reported before ( Augé 1987). The remaining material previously assigned to C. rugosus (one maxilla, one frontal and two vertebrae) all possess gekkotan features.

The diagnostic characters of the genus Cadurcogekko are, according to Augé (2005): the rugose surface of the facial process of the maxilla, an elongated groove associated with the most posterior neurovascular foramen of the maxilla, a postnarial anterodorsal depression of the maxilla, and presence of a supradental gutter. Thus, most diagnostic characters reported by Augé (2005) for C. rugosus focus on the maxilla. USTL, PRA 9 presents the diagnostic characters of Cadurcogekko , and its smaller size, the lower tooth-count and a coarser ornamentation relative to the type species have been interpreted as characters of interspecific variation ( Augé 2005; Daza et al. 2014). Augé (2005) already noted that C. piveteaui and C. rugosus were quite different and he expressed some doubts about the taxonomic position of C. rugosus . The similarities of the maxillae, shared only by these two species, were considered enough evidence for generic referral, but it is clear now that the contradiction between having a similar maxilla and exhibiting strong differences in the dentary was because the latter bone belonged to a different taxon, rendering C. rugosus a chimaera. A review of the maxillary characters supports the referral of USTL, PRA 9 to Cadurcogekko , and its status as a different species from C. pivetaui , but the identity of the rest of material is more problematic. Augé (2005) provided no explicit reasons to refer the vertebrae and dentary fragment to C. rugosus . The main reason for the referral was indeed that they represented supposedly gekkotan material from the same locality as the type specimen. Because C. piveteaui has been also identified at Sindou D ( Augé 2005), the smaller size—comparable to that of the maxilla—of the additional material (vertebrae and frontal) was used to discriminate between the two forms.

As explained above, the type dentary and the referred fragmentary dentary are no longer considered gekkotan, and identification of the rest of gekkotan material as part of Cadurcogekko is difficult. The only exception is the frontal. Augé (2005) noted that the size of this frontal was smaller to that of C. piveteaui . Ornamentation of the frontal from Sindou D closely matches that of the maxilla from Les Pradigues (here proposed as the holotype of C. verus ). Likewise, some substantial differences of dermal ornamentation and frontal morphology serve to differentiate the currently recognized Cadurcogekko species ( Daza et al. 2014). The referral of the non-diagnostic material (two dorsal vertebrae) to one of the two species of Cadurcogekko present at the locality is even more difficult, and can only be justified in terms of size. Because there is no argument in favor or against this specific allocation, we accept Augé’s (2005) original referral as correct until new evidence sheds light on this issue.

Figures

FIGURE 1. Holotype (right maxilla) of Cadurcogekko verus (USTL, PRA 9) in labial (A) and lingual (B) views, from Les Pradigues (MP 17). Scale bar in mm.

FIGURE 2. Partial left dentary of Cadurciguana hoffstetteri (USTL, SND 625) in labial (A) and lingual (B) views, from Sindou D (MP 18 - 19). Scale bar in mm.