Gli squali fossili
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.
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.
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.
© 1999-2013 www.squali.com di Antonio Nonnis