Taxonomy and Intraspecific Variation of Macrocephalites Formosus (Sowerby) from the Jurassic Chari Formation, Kutch, Western India

Macrocephalites Zittel, 1884, an important genus in Kutch biostratigraphy, shows considerable diversity at species level. Macrocephalites formosus (Sowerby) is one species which shows a wide range of variability of different morphological characters. A detailed statistical analysis of the principal biocharacters of 140 individuals collected from different localities of Kutch was made to assess quantitatively the range of variation of the species.  "Macrocephalites chariensis (Waagen)", which was previously designated as a separate species, is demonstrated here to be a variant of Macrocephalites formosus and is incorporated into the latter species. An attempt is made to delineate the generic characters of Macrocephaliles and describe the diagnostic characters of the species M. formosus in detail. The variability of the species has no obvious adaptive significance.