Delpitoscyllium planum ( Davis, 1890 )

Adolfssen, Jan S. & Ward, David J., 2015, Neoselachians from the Danian (early Paleocene) of Denmark, Acta Palaeontologica Polonica 60 (2), pp. 313-338 : 325

Delpitoscyllium planum ( Davis, 1890)

Fig. 5A–E .

1890 Scyllium planum sp. nov.; Davis 1890: 383, pl. 38: 9.

Material.— Davis’ specimen from Terkelskov, Denmark ( MGUH 1400 ), further four specimens from Faxe ( OESM-10046-19 , OESM-10046-20 , OESM-10046-21 , OESM-10046-22 ), and additional specimens in the collection of Alice Rasmussen, Faxe (Br2) .

Description.—Symmetrical teeth with a prominent main cusp flanked by one to two pairs of cusplets.The teeth are sigmoidal in lateral view and the furrows between the cusplets and the main cusps create a median labial depression in the crown.The apron is weakly bifid and strongly overhangs the root.

In anterior teeth the crown is longer than wide with only one pair of converging cusplets, whereas lateral teeth are wider and the cusplets are either erect or diverging. Posterior teeth have a second pair of small cusplets and the crown becomes progressively wider and slightly asymmetrical. Both the labial and the lingual faces are smooth and convex, the lingual face particularly so. In none of the specimens is the root preserved. The lingual face has a well-developed median protuberance

Remarks.— Noubhani and Cappetta (1997) erected a new genus, Delpitoscyllium , for the species Ginglymostoma africanum Leriche, 1927 due to the lower number of cusps, “not exceeding two pairs” and a median labial keel on the main cusp. Though lacking the keel, present in the Moroccan material, we have transferred Scyllium planum Davis, 1890 to this genus. D. planum is regarded as a separate species and it is separated from the partly coeval species Delpitoscyllium africanum by the presence of a median keel on the apex of the labial crown. It could be that this character is variable among populations and that the two species of Delpitoscyllium are synonymous, in which case D. planum ( Davis, 1890) is the senior synonym.

Amongst the Moroccan material depicted by Arambourg (1952: pl. 22: 8), there is a wide posterior tooth similar to what is observed in the Danish material. The median keel is present in specimens from the French Thanetian figured by Moreau and Mathis (2000).

Stratigraphic and geographic range.—Currently only recorded from the Danian (early Paleocene) of Denmark.

Figures

Fig. 5. Orectolobiformes and Heterodontiformes from the Danian of Stevns Kridtbrud, Kulstirenden, Faxe kalkbrud, and Terkelskov Kalkvaerk. A–E. Delpitoscyllium planum (Davis, 1890). A. MGUH 1400, holotype (Br2) anterior tooth in labial (A 1), basal (A 2), and lateral (A 3) views. B. OESM-10046-20 Br2) anterior tooth in labial (B 1), basal (B 2), and lateral (B 3) views. C. OESM-10046-21 (Br2) anterior tooth in labial (C 1), basal (C 2), and lateral (C 3) views. D. OESM-10046-19 (Br2) lateral tooth in labial (D 1), basal (D 2), and lateral (D 3) views. E. OESM-10046-22 (Br2) posterior tooth in labial (E 1), basal (E 2), and lateral (E 3) views. F–H. Heterodontus rugosus (Agassiz 1843). F. MGUH 29848 (Ce) anterior tooth in labial (F 1), lingual (F 2), and lateral F 3) views. G. MGUH 29849 (Ce) lateral tooth in occlusal view. H. MGUH 29850 (Ce) lateral tooth in labial (H 1), occlusal (H 2), and lateral (H 3) views., J. Heterodontus sp. I. MGUH 298451 (Br2) anterior tooth in labial view. J. OESM-10046-13 (Br2) lateral tooth in occlusal view.