FIGURE 6 in A fragmentary leptonectid ichthyosaurian from the lower Pliensbachian of Luxembourg

FIGURE 6. Diagnostic dental features of Early Jurassic ichthyosaurians with small and elongated tooth crowns. The distribution of concave ring at the level of the acellular cementum ring, which we term here "annulus" (indicated by orange arrows) appears restricted to leptonectids but are not fully expressed in all the teeth of an individual. (A) OUM J10305. (B) BRSMG Ce9856. (C) NHMUK R PV14370. (D) drawing extracted from Fraas (1892). (E) MNHNL LM226. (F) MNHNL TU112. (F) SMNS 81965. (H) MNHNL TV178.