Xiphodolamia barbadica (Casier, 1958)

Artüz, M. Levent & Sakinç, Mehmet, 2025, Description of a new species, Xiphodolamia maliki sp. nov. and the shark teeth of Middle Eocene (Lutetian) aged Soğucak Formation in Küçükçekmece, Istanbul, Turkey, Zootaxa 5646 (4), pp. 527-544 : 538

Xiphodolamia barbadica

The fossil teeth of Xiphodolamia barbadica lack lateral cusplets and feature a deep, prominent transverse groove. The tooth cervix, defined as the distance between the basal ledge and the root, is distinctly visible on the labial view, while it appears narrower on the lingual view. On the labial side, the basal ledge is positioned lower, with noticeable transverse ridges extending across the surface.

The tooth exhibits an orthodont structure, with an enameloid layer constituting approximately 1/1053 of the total tooth length. The enameloid is relatively thick and displays folds on its labial surface. The enameloid layer is approximately 1/11 the thickness of the pallial dentin. The pallial dentin layer is robust and rigid, making up about 1/96 of the total length, and shows no porosity. The orthodentin layer, which accounts for roughly 1/8 of the tooth length, contains well-organised small dentinal tubules. These tubules have a diameter ratio of approximately 1/10 compared to other tubules scattered throughout the orthodentin and distributed in the axial direction. They are aligned in a single row at the pallial dentin-orthodentin junction, both peripherally and in the axial plane ( Fig. 8A, 8B /e). A thin pulp cavity runs axially through the tooth and is nearly the same thickness as the dentinal tubules ( Fig. 8A; 8B ). The osteodentin in the root is rigid and exhibits a homogeneous structure.

Figures

FIGURE 8. Internal tooth structure of Xiphodolamia barbadica (right anterolateral tooth) A (Axial) and B (Transversal) in back-scattered mode, Xiphodolamia ensis (right anterolateral tooth) C and D, Xiphodolamia eoceana (left anterolateral tooth) E and F, and Xiphodolamia maliki sp. nov. (right anterolateral tooth) G and H in axial views and labiolingual axial cross-sections at the neck of the tooth. a) Enameloid; b) Pallial dentin; c) Orthodentin with dentinal tubules; d) Pulp cavity; e) Single row of dentinal tubules at the interface between pallial dentin and orthodentin (pallial dentin–orthodentin junction). Scale bar 500 µm.