Paraplacosauriops quercyi (Filhol, 1882)
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publication ID |
https://doi.org/ 10.5252/geodiversitas2021v43a9 |
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publication LSID |
urn:lsid:zoobank.org:pub:11D0D852-39D7-449C-9EB3-C3D804114556 |
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DOI |
https://doi.org/10.5281/zenodo.4721229 |
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persistent identifier |
https://treatment.plazi.org/id/03A1633B-FFBE-FFDF-30D7-F909FE833FE6 |
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treatment provided by |
Felipe |
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scientific name |
Paraplacosauriops quercyi (Filhol, 1882) |
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Paraplacosauriops quercyi (Filhol, 1882) ( Figs 23-29 View FIG View FIG View FIG View FIG View FIG View FIG View FIG )
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 View FIG ; 24 View FIG )
About the anterior half of the maxilla is preserved, however, its anteriormost portion is missing ( Figs 23 View FIG ; 24 View FIG ). The external wall of the maxilla consists of two complete and three incomplete ornamented shields divided by more or less distinct grooves ( Figs 23A View FIG ; 24A View FIG ). 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 View FIG ). 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 View FIG ; 24A View FIG ).
The smooth medial surface bears two depressions; a large one anteriorly (lacrimal recess) and a smaller one posteriorly ( Figs 23B View FIG ; 24B View FIG ). 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 View FIG View FIG View FIG View FIG View FIG )
The right dentary NHMW 2019/0049/0001 is almost completely preserved, with only several pieces of the posteriormost portion are missing ( Figs 25-28 View FIG View FIG View FIG View FIG ), while the left dentary NHMW 2019/0049/0002 is much more incomplete, missing both anterior and posterior portions ( Fig. 29 View FIG ). 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 View FIG View FIG View FIG View FIG ). 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 View FIG ; 28A View FIG ).
The most distinctive feature of the dentary is a huge alveolar canal ( Figs 25-28 View FIG View FIG View FIG View FIG ). 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 View FIG View FIG View FIG View FIG ). The posteroventral margin of the intramandibular septum extends to a distinct posterior spine ( Figs 25-28 View FIG View FIG View FIG View FIG ). 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 View FIG View FIG View FIG ). The teeth are dorsoventrally straight and they increase in size mesiodistally ( Figs 25-28 View FIG View FIG View FIG View FIG ). 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 View FIG View FIG View FIG View FIG ). 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.
No known copyright restrictions apply. See Agosti, D., Egloff, W., 2009. Taxonomic information exchange and copyright: the Plazi approach. BMC Research Notes 2009, 2:53 for further explanation.