Formerly known (1975-90s) to North American collectors as Plicatolamna arcuata, or more recently, Cretodus arcuatus, these somewhat uncommon Cretaceous teeth are now ascribed to Archaeolamna kopingensis (DAVIS, 1890). Davis (pp 390-91) originally named these teeth Odontaspis kopingensis however, Woodward's 1894 description of Lamna arcuata came into common usage. Cappetta & Case 1975 attributed NJ specimens to Herman's (1975) newly erected genus as Plicatolamna arcuata. Cappetta (1987:98) citing Herman (1977:196-206) reluctantly moved arcuata to Cretodus; Kent (1994:50) did the same.

When studying tooth-sets, Siverson (pers com 1999) found that these lamnoid teeth were part of a primitive, odontaspidid-like dentition. Citing ICZN article 79 C [2], he (1992:529-534) erected a new genus (Archaeolamna) and reverted to the senior synonym (kopingensis).

This genus is known from Albian to Maastrichtian sediments of Europe, North America and Australia, generally from isolated teeth only; Cook et al (2011) described a partial skeleton from the Pierre Shale of Kansas. A single species have been attributed to the western North Atlantic -- Archaeolamna kopingensis. Teeth from this species dating to the Maastrichtian of the Western Interior Seaway (Wyoming and Montana) vary from their Atlantic counterparts and have been placed in the subspecies A. k. judithensis. SIVERSON 1992

Underwood & Cumbaa (2010) reported upon a very large cache of these teeth from the Cenomanian of Saskatchewan. The authors proposed a reconstructed tooth-set, but there appear to be gaps in the lateroposterior positions. However, it does provide a group of very good positional examples present in the genus. Cook et al (2011) depicted the Archaeolamna dentition using articulated material.

As alluded to earlier, the genus does not have the relatively simple tooth-set seen in living lamnoids. Rather, an odontaspid-like, complex grouping of teeth is present. It incorporates small symphyseal? / parasymphyseals, intermediates and posterior teeth and enlarged anterior and laterals.

In general, the teeth of A. kopingensis have bilobate roots with a U-shaped basal margin and a lingual protuberance. Some teeth show evidence of a very weak nutrient groove. The cusp is triangular and elongated with a pair of triangular cusplets and complete cutting edge. Except for some posterior teeth, the crown are smooth (without wrinkles).

The upper anteriors have a weak distal bend with symmetrical roots and the lowers are more erect with less symmetrical roots. Upper laterals bend more strongly towards the commissure and the roots are shorter with an obtuse basal margin. Lower laterals are more erect than the uppers and the mesial lobe is often elongated. Posterior teeth are much smaller than the anteriors and laterals with a distally directed cusp and often lacking a cusplet on the mesial shoulder.

Selected References