Opisthias Gilmore 1909

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.