Scincoidea, Oppel, 1811

Augé, Marc Louis, Dion, Michaël & Phélizon, Alain, 2021, The lizard (Reptilia, Squamata) assemblage from the Paleocene of Montchenot (Paris Basin, MP 6), Geodiversitas 43 (17), pp. 645-661 : 649

publication ID	https://doi.org/ 10.5252/geodiversitas2021v43a17
publication LSID	urn:lsid:zoobank.org:pub:E0BAA274-37CB-407B-849A-FD284BBE954B
DOI	https://doi.org/10.5281/zenodo.5636445
persistent identifier	https://treatment.plazi.org/id/0F23E968-FF81-FF9A-FBB3-7D08D5E9F938
treatment provided by	Felipe
scientific name	Scincoidea
status

Treatment

? Scincoidea indet.

MATERIAL EXAMINED. — MNHN. F.MTC242, one incomplete axis ( Fig. 4 View FIG ).

DESCRIPTION

Terminology follows Hoffstetter & Gasc 1969 and Čerňanský et al. 2014.

The centrum is well-preserved and strongly built but the neural arch is entirely lacking. A posteroventrally oriented intercentrum (second intercentrum) is sutured (not fused) to the base of the centrum and forms a rather short ventral keel in the antero-ventral region of the centrum. A small, slightly anteriorly curved process is fused to the posterior part of the base of the centrum, nearly beneath the condyle articulation. These two reliefs are separated by a deep, rounded trench.

The huge odontoid process covers most of the articulation area in anterior view, it is high (dorso-ventrally elongated) and not markedly expanded anteriorly. In posterior view, the condyle is laterally compressed.

REMARKS

According toČerňanský 2016 the squamate atlas-axis complex may be an important source of new morphological characters that can help to resolve persistent conflicts between morphological and molecular phylogenetic analyses of lizard phylogeny ( Losos et al. 2012). However, only a handful of morphological studies include detailed anatomy of the atlas-axis complex in lizards ( Rieppel 1980, Čerňanský et al. 2019, anguimorph lizards; Čerňanský et al. 2014;Čerňanský 2016; Čerňanský & Stanley 2019 about the atlas-axis in chamaeleonids, Cordyliformes and dibamids respectively; Vaugh et al. 2015, geckos). The work of Hoffstetter & Gasc 1969 develops a wide-ranging comparative study of the atlas-axis complex between lizard families.

The axis from Montchenot bears several phylogenetic significant characters: odontoid process dorso-ventrally elongated; condyle laterally compressed (occurs in nearly all Cordyliformes, Čerňanský 2016: 22); position and suture of intercentra on the ventral region of the centrum. Among Anguimorpha , the intercentra are fused to the centrum in anguid lizards and in varanids the odontoid process is laterally elongated. The condyle of lacertoid lizards is rather rounded and not laterally compressed and most gekkonids have amphicoelous vertebrae. All characters of this axis suggest scincoid relationships. For example, the morphology of the axis of Broadleysaurus (Cordyliformes, Gerrhosauridae ) is very similar to that of the axis from Montchenot (Čerňanský 2016: fig. 8). However, this referral is at best tentative due to the incompleteness of MNHN.F.MTC242 and the very limited number of specimens available for comparisons.