Paraplacosauriops quercyi
Creators: name: Georgalis, Georgios L.
name: Čerňanský, Andrej
name: Klembara, Jozef
Publisher: name: Zenodo
Year: 2021
Subjects: Biodiversity
Taxonomy
Animalia
Chordata
Reptilia
Squamata
Anguidae
Paraplacosauriops
Paraplacosauriops quercyi

description: Paraplacosauriops quercyi (Filhol, 1882) (Figs 23-29)
REFERRED SPECIMENS. — An incomplete left maxilla (NHMW 2019/0049/0003); a right dentary (NHMW 2019/0049/0001); a left dentary (NHMW 2019/0049/0002).
DESCRIPTION
Maxilla (Figs 23; 24)
About the anterior half of the maxilla is preserved, however, its anteriormost portion is missing (Figs 23; 24). The external wall of the maxilla consists of two complete and three incomplete ornamented shields divided by more or less distinct grooves (Figs 23A; 24A). One of the shields lying between the two anterior and two posterior shields is the largest and is of pentagonal shape. The ornamentation consists of small tubercles (Fig. 23E). The ornamented surface is ventrally delimited by a shallow and narrow, anteroposteriorly running groove. Immediately ventral to the groove, the surface of the maxilla is smooth and four labial foramina are present there (Figs 23A; 24A).
The smooth medial surface bears two depressions; a large one anteriorly (lacrimal recess) and a smaller one posteriorly (Figs 23B; 24B). The supradental shelf is straight and the bone immediately laterally to the posterior portion of the shelf is burrowed by the superior alveolar canal. The teeth are mesiodistally narrow and the apex is pointed.
Dentaries (Figs 25-29)
The right dentary NHMW 2019/0049/0001 is almost completely preserved, with only several pieces of the posteriormost portion are missing (Figs 25-28), while the left dentary NHMW 2019/0049/0002 is much more incomplete, missing both anterior and posterior portions (Fig. 29). Accordingly, we base our description on the almost complete right dentary NHMW 2019/0049/0001. The dentary is massively built. Its external surface is smooth. A distinct groove runs immediately anteroventrally to the root portion of the coronoid process (Figs 25-28). From there, a shallow sulcus runs anteriorly along the dorsal crest of the dentary. Ventrally to this sulcus, five labial foramina are present. The coronoid process is small and short. The posteriormost portion of the dentary has an almost perpendicular margin and represents a surangular process (Figs 26C, D; 28A).
The most distinctive feature of the dentary is a huge alveolar canal (Figs 25-28). The intramandibular septum runs in dorsolateral-ventromedial direction and, in the place of the alveolar foramen, it is distinctly embayed anteriorly. The ventral margin of the intramandibular septum is divided from the wall of the dentary by a distinct groove (Figs 25-28). The posteroventral margin of the intramandibular septum extends to a distinct posterior spine (Figs 25-28). The dental crest extends medioventrally. The Meckel’s groove opens medioventrally.
There are 22 tooth positions, while at least 10 teeth are rather well preserved (Figs 25-27). The teeth are dorsoventrally straight and they increase in size mesiodistally (Figs 25-28). The most robust are the 3rd and 4th teeth from posterior. The lingual walls of the teeth are medially bulged. The apices become mesiodistally gradually more robust and bear distinct mesiodistally straight cutting edges (Figs 25-28). The lingual and labial surfaces of the apices are distinctly striated.
REMARKS
The almost complete dentary NHMW 2019/0049/0001 bears strong resemblance with the neotype dentary of Para- placosauriops quercyi (MNHN.F.QU16569). Most characteristically, both specimens share the strongly heterodont dentition, with the anterior teeth being much slender and the posterior ones robust, a developed intramandibular septum, with its ventral margin fused to the floor of the Meckel’s groove (Augé & Sullivan 2006). The fragmentary dentary NHMW 2019/0049/0002, although much incomplete, seems to possess also this dental morphology. The general morphology of the preserved portion of the maxilla and the type of ornamentation correspond to those described by Augé & Sullivan (2006).
The specimen NHMW 2019/0049/0001 represents the most complete dentary assigned to Paraplacosauriops quercyi and thus, enhances our understanding of this element in this melanosaurine taxon. We agree with recent authors that the species Diploglossus cadurcensis De Stefano, 1903, and Placosaurus leenhardti Leenhardt, 1926 (both from the old collections of the Phosphorites du Quercy) are junior synonyms of Paraplacosauriops quercyi (e.g., Augé 2005), although we have to highlight that the completeness of the holotype of Placosaurus leenhardti is remarkable and this taxon is certainly worth of a comprehensive redescription.
description: Published as part of 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, pp. 219-293 in Geodiversitas 43 (9) on pages 246-247, DOI: 10.5252/geodiversitas2021v43a9, http://zenodo.org/record/4720776