Xiphodolamia maliki, Artüz & Sakinç, 2025

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 : 540

Xiphodolamia maliki sp. nov.

In Xiphodolamia maliki sp. nov. fossil teeth, there are no lateral cusplets, and the transverse groove is thin and narrow. The tooth cervix is a fine line on both the labial and lingual views ( Fig. 7 a-d). In apical teeth, it forms a distinct "D" shape in lateral section, with the flat side facing the lingual side. Unlike other species in the genus, X. maliki sp. nov. lacks transverse ridges on the labial view, with an all-around smooth surface below the basal ledge.

The tooth exhibits an orthodont structure, with the external surface covered by a robust and smooth enameloid layer, free of folds on both the labial and lingual surfaces. The enameloid layer constitutes approximately 1/12 of the thickness of the pallial dentin layer. The pallial dentin layer is rigid and represents a ratio of about 1/87 of the total tooth length. The orthodentin layer has a slightly porous structure, with irregularly arranged, sparse, and thin tubules, containing a pulp cavity that extends from the root to the apex, accounting for a diameter ratio of approximately 1/10 of the total tooth length. The proportions of the enameloid and orthodentin to the total tooth length are 1/1072 and 1/8, respectively. The osteodentin in the root is sparsely porous ( Fig. 8G, 8H ).

Figures

FIGURE 7. Xiphodolamia maliki sp. nov. (a–d) Holotype: LA60-001.00, anterior tooth. a) labial view; b) mesial view; c) distal view; d) lingual view. (e–f) selected mandibular lateral teeth; e) labial view; f) lingual view. (g–h) selected maxillar lateral tooth; g) labial view; h) lingual view. (j–m) selected maxillar intermediate tooth; j) lingual view; k) labial view; l) mesial view; m) distal view. (Scale bar 10 mm)

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.