Echinodon sp.

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 : 709

Echinodon sp.

( Fig. 21 A-D)

DESCRIPTION

Premaxillary teeth

Two well-preserved, isolated heterodontosaurid premaxillary teeth (ANG15-R672 & ANG14-3368) were recovered in Angeac-Charente ( Fig. 21 A-D). Only the crown, possibly from a shed tooth, is preserved in the first one ( Fig. 21A, B ), the other also shows a part of the root ( Fig. 21C, D ). Both crowns are very similar in being swollen and recurved folidont ( Hendrickx et al. 2015a). They are rather short with a mesiodistal basal length of 6 mm and 7.5 mm and a preserved crown height of 8 and 9 mm, respectively. The teeth resemble those of Echinodon from the Purbeck Group of England described by Norman & Barrett (2002) and Sereno (2012). The crown is slightly concave lingually and gently convex labially, with an elliptical cross-section at mid-height. The main axis of the crown is recurved distally, so that its apex is slightly distal to the center of the crown base.The apex is blunt and bears a wear facet lingually.In lingual and labial views, the mesial border of the crown is convex with a bulge at its base, whereas the distal border is concave.As in Echinodon ( Sereno2012) , and in contrast to many ornithischians, the carinae of the premaxillary teeth do not bear denticles ( Galton 2009). The marked lingual wear facet, presumably from occlusion with the predentary bill, is apicobasally oriented ( Sereno 2012). The crown enamel ends at the same level on every surface. The enamel has a relatively smooth texture, but exhibits small striations.

At the cervix, a slightly pronounced constriction separates the crown from the base of the root. The latter being incomplete in one specimen and lacking in the other, we cannot assess its length relatively to the length of the crown. The base of the root is large. The root labiolingual width is stable along the preserved section, practically equivalent to the crown mesiodistal basal length, and slightly inferior to the maximum width of the crown. The root is labiolingually narrower than mesiodistally wide. In lingual and labial views, it has subparallel and slightly convex borders. At the fracture point, the root has an oval cross-section with a large pulp cavity.

Figures

FIG. 21. — Ornithischian teeth from Angeac-Charente: A, B, Heterodontosaurid premaxillary tooth of Echinodon sp. (ANG15-R671) in lingual (A) and labial (B) views; C, D, Heterodontosaurid premaxillary tooth of Echinodon sp. (ANG14-3368) in lingual (C) and labial (D) views; E, F, hypsilophodontid premaxillary tooth (ANG M-119) in lingual (E) and labial (F) views; G, H, hypsilophodontid dentary tooth (ANG15-R927) in labial (G) and lingual (H) views; I-L, hypsilophodontid maxillary tooth (ANG 10-153) in lingual (I), distal (J), labial (K) and mesial (L) views. Scale bars: A-D, I-L, 5 mm; E-H, 3 mm.