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Gli squali fossili

Cretolamna

GLIKMAN 1958
Extinct mackerel shark
Lwr Cretaceous - Lwr Eocene
Ordine Famiglia
Lamniformes BERG 1958 Cretoxyrhinidae GLIKMAN 1958

This genus has a worldwide fossil record, but is limited to isolated teeth and vertebral centra. The teeth of C. appendiculata (AGASSIZ 1843) are common in Cretaceous marine exposures (extending into the Paleocene in Europe and Lower Eocene of Africa), including those of the Middle Atlantic States, and easily identified. Cappetta (1987) notes that other members of this genus are more localized in time and distribution. In addition to C. appendiculata, North Carolina sediments yield C. biauriculata maroccana ARAMBOURG 1935, as do those of Texas (Noubhani & Cappetta 1997).

Welton & Farish (1993) include C. appendiculata and C. woodwardi HERMAN 1977 in their Cretaceous fauna. Siverson (1996) deemed C. woodwardi synonymous with Pseudoisurus tomosus GLIKMAN 1957 and was of the opinion that these Texas teeth, ascribed to C. woodwardi, were in fact, C. appendiculata.

Kent (1994) further expands the possibilities in the Chesapeake region by listing five species: C. appendiculata, C. appendiculata lata (AGASSIZ 1843), C. appendiculata pachyrhiza HERMAN 1977, C. biauriculata maroccana and C. lerichei (CASIER 1946). Following Landemaine (1991), the later species has been included under Serratolamna.

The teeth of C. appendiculata (no attempt will be made to differentiate the sub-species) are best characterized by their smooth triangular cusp, broad triangular lateral cusplets and a bilobate root, which has a lingual protuberance and foramen but lacks a nutrient groove. The crown of anterior teeth is elongated and erect and in laterals, the cusp is shorter and distally directed (more acutely in upper teeth). The basal margin of the root is "U" in shape.
 

Fig. 1 - Big Brook, Monmouth Co., NJ
Anterior 18.0 and lateral 16.0 mm in height


Cretolamna biauriculata teeth are said to be found in North Carolina, but are much less common. They are identifiable by their dual lateral cusplets and weakly concave basal root margin. The below specimen cannot be positively identified by the author as C. biauriculata. It was found in tailings that produce teeth of Serratolamna serrata (AGASSIZ 1843). Welton & Farish (1993) include a lateral tooth of that species which is very similar to the those of C. biauriculata. A variation of the tooth-design depicted below is included in the S. serrata section.

Fig. 2 - Cretolamna biauriculata
or Serratolamna serrata
Lateral - 17.5 x 21.0 mm
Black Creek Group, No Carolina



On rare occasions, the chalk of Kansas yields a Cretolamna tooth. Time wise (late Coniacian) these should be ascribed to C. appendiculata, however its crowns can be quite broad.

Welton & Farish found teeth similar to those illustrated below in the Turonian of Texas and listed them as C. woodwardi, but speculated that they might be C. appendiculata. A similar difficulty was encountered with the these Smoky Hill anteriors. Mikael Siverson (pers. com.) felt certain that these teeth are C. appendiculata noting the deep-water environment. Note how much broader these crowns are than on their Campanian and Maastrichtian counterparts.
 
Fig. 3 & 4 - Cretolamna appendiculata
Smoky Hill Chalk, Niobrara Formation, Kansas

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