Gregoryceras Spath, 1924

Cecca, Fabrizio & Savary, Bérengère, 2007, Palaeontological study of Middle Oxfordian- Early Kimmeridgian (Late Jurassic) ammonites from the Rosso Ammonitico of Monte Inici (north-western Sicily, Italy), Geodiversitas 29 (4), pp. 507-548 : 528-529

Genus Gregoryceras Spath, 1924

TYPE SPECIES. — Ammonites transversarius Quenstedt, 1847.

REMARKS

The Sicilian specimens of the genus Gregoryceras originally described by Gemmellaro (1877) have been recently revised by D’Arpa & Meléndez (2002). These authors have proposed a Gregoryceras -based biostratigraphic scale on the basis of the Sicilian specimens and on the revision of the literature ( D’Arpa & Meléndez 2004), focusing on the species G. riazi (de Grossouvre, 1917) , G. transversarium (Quenstedt, 1847) and G. fouquei (Kilian, 1889) . More recently, the systematics of the genus Gregoryceras has been almost entirely revised (with the exception of the fouquei group) by Bert (2004) on the basis of material collected in SE France. This author also proposes an accurate biostratigraphical correlation of the vertical succession of Gregoryceras species with the Submediterranean zonation. It is worth noting that Bert’s biostratigraphical conclusions are based on the co-occurrence of Gregoryceras representatives together with Submediterranean perisphinctids in SE France. This author distinguishes different chronospecies, corresponding to segments of a substantially anagenetic line within the genus Gregoryceras . The limits between these species are not easy to recognize and the stratophenetic succession proposed by Bert cannot be tested in the Mediterranean regions because a succession of species as complete as the one available in SE France has not been discovered yet.

The systematic and biostratigraphic conclusions of Bert (2004) are accepted in this paper and the proposed chronospecies succession from G. iteni Jeannet, 1951 up to G. devauxi is adopted. The conclusions of D’Arpa & Meléndez (2002, 2004) about the group of G. fouquei are also taken into account here.