Opisthias, Gilmore, 1909

Allain, Ronan, Vullo, Romain, Rozada, Lee, Anquetin, Jérémy, Bourgeais, Renaud, Goedert, Jean, Lasseron, Maxime, Martin, Jeremy E., Pérez-García, Adán, Fabrègues, Claire Peyre De, Royo-Torres, Rafael, Augier, Dominique & Bailly, Gilles, 2022, Vertebrate paleobiodiversity of the Early Cretaceous (Berriasian) Angeac-Charente Lagerstätte (southwestern France): implications for continental faunal turnover at the J / K boundary, Geodiversitas 44 (25), pp. 683-752 : 701-702

cf. Opisthias

( Fig. 14 )

DESCRIPTION

ANG M-120 ( Fig. 14 ) is a posterior dentary fragment bearing two preserved acrodont teeth in addition to seven broken teeth, there are six anteriorly and one posteriorly.Tooth crowns are sub-pyramidal in shape, angulous anteriorly, more rounded posteriorly, and slightly inclined anteriorly throughout the dentition ( Fig. 14A ). As suggested by tooth bases, teeth are gradually increasing in size posteriorly. In occlusal view, the tooth row is straight ( Fig. 14C ). The coronoid process is broken at its base and the mandibular ramus is broken ventrally at the level of the Meckelian groove ( Fig. 14B ).

ANG M-120 is here tentatively referred to cf. Opisthias because of the tooth morphology and gradual heterodonty pattern which is similar to that observed in previously described Opisthias dentaries ( Gilmore 1910; Evans & Fraser 1992). In lateral view, the dentary of Homoeosaurus shows wider tooth bases and crown apices that are less acute and not anteriorly inclined (Cocude-Michel 1963). Tingitana from the Tihonian-Berriasian of Morocco, has dentary teeth bearing a strong, inwardly concave, anterolingual crest between a large posterior cone and a small anterolingual one (Evans & Sigogneau-Russell 1997). It is worth noting that a sphenodontian from Cherves-de-Cognac, represented by a partial skeleton, was referred to Homoeosaurus by Buffetaut et al. 1989. A revision of this material, housed in a private collection, including a detailed comparison with the Angeac-Charente specimen would be useful to assess sphenodontian diversity in western Europe.

Figures

FIG. 14. — Rhynchocephalian right dentary fragment from Angeac-Charente: A-C, cf. Opisthias sp. (ANG M-120) in labial (A), lingual (B) and dorsal (C) views. Scale bar: 2.5 mm.