Archaeolamna sp.

Vullo, Romain, Cappetta, Henri & Néraudeau, Didier, 2007, New sharks and rays from the Cenomanian and Turonian of Charentes, France, Acta Palaeontologica Polonica 52 (1), pp. 99-116 : 104-105

Archaeolamna sp.

Fig. 2C .

Material.—One tooth (UM AMA 2) from l’Amas, Roullet– Saint−Estèphe, Upper Cenomanian D; a few unnumbered incomplete teeth from Les Renardières, Tonnay−Charente, Lower Cenomanian B1, and from Vauban cliff, Fouras and Traslemaine, Champniers, Lower Cenomanian B2.

Description.—The illustrated lateral tooth (UM AMA 2) shows a relatively narrow cusp curved toward the commissure. The lingual face of the cusp is convex, and the labial face is flat. Both faces are smooth. There is one pair of strong, triangular lateral cusplets. The root is thick and has a well−developed medio−lingual protuberance. The lingual neck is narrow, nearly as much at the centre of the cusp as near the margins. The two lobes are clearly distinct, separated by a rounded basal notch. In the anterior files, the teeth have a more erect cusp and a less laterally expended root.

Remarks.—The genus Archaeolamna was originally erected by Siverson (1992) for the reassignment of the Davis’ species Odontaspis kopingensis , from the Campanian of Sweden. This genus occurs commonly from the Albian to the Maastrichtian in numerous regions ( Siverson 1992, 1996, 1997; Biddle 1993). A second species, A. haigi Siverson, 1996 , has been recently described from the Cenomanian of Australia, beside teeth tentatively referred to A. kopingensis ( Siverson 1996) . Conversely to A. kopingensis , A. haigi have lingually folded teeth. Zhelezko (1990) has described three species and subspecies, Archaeolamna aduncata , A. aduncata suberecta , and A. arcuata orica from the Santonian of western Kazakhstan, under the generic name of Protolamna Cappetta, 1980c . Due to the poor quality of the Zhelezko’s illustrations, it is difficult to evaluate the validity and mainly the morphological differences between species. According to Mikael Siverson (1996, personal communication 2006), this material entirely corresponds to the type species A. kopingensis . The specimen UM AMA 2 is also similar to the lateral teeth of Dwardius Siverson, 1999 , but it cannot be assigned to this monospecific genus owing to its relatively slenderer cusp and its narrower neck at the centre of the cusp (see Siverson 1999). In Dwardius woodwardi ( Herman, 1977) , the neck is indeed much more developed below the cusp than marginally. Due to the scarcity of the Charentes material, it is here considered preferable to leave the specimens in open nomenclature, as Archaeolamna sp.

Figures

Fig. 2. Teeth of the hemiscylliid Almascyllium Cappetta, 1980a, the ginglymostomatid Cantioscyllium Woodward, 1889, the cretoxyrhinid Archaeolamna Siverson, 1992 and the anacoracid Squalicorax Whitley, 1939 from the Cenomanian and Turonian of Charentes, SW France. A. Almascyllium sp., Font−de−Benon, Lower Cenomanian; labial view of UM FBN 1. B. Cantioscyllium cf. decipiens Woodward, 1889, l’Amas, Upper Cenomanian; labial (B1), and occlusal (B2) views of UM AMA 1. C. Archaeolamna sp., l’Amas, Upper Cenomanian; labial (C1), and lingual (C2) views of UM AMA 2. D. Squalicorax baharijensis Stromer, 1927, Le Mas, Upper Cenomanian; labial (D1), and lingual (D2) views of UM LMS 1. E. Holotype of Squalicorax coquandi sp. nov., Port−des−Barques, basal Turonian; labial (E1), distal (E2), and lingual (E3) views of UM PDB 1. F. Squalicorax cf. intermedius Glückman in Glückman and Shvazhaite, 1971, Le Puits des Insurgés, Upper Cenomanian; labial (F1), mesial (F2), and lingual (F3) views of UM PDI 1.