Dimorpharaea de Fromentel, 1861 (Scleractinia, Anthozoa) from the Middle Jurassic of Kachchh, India

The current classification of scleractinian corals based upon gross morphological features has been found unsatisfactory due to additional information from skeletal microarchitecture and microstructure. It is necessary to investigate microstructural details and limits in morphologic variation within and between different coral clades before a revised classification is constructed. Variations in morphologic characters and microstructural details from a population of Dimorpharaea de Fromentel, 1861 (Family Microsolenidae) from Upper Bathonian (Jumara Dome) strata in Kachchh are described. The data used include the diameter(D) and height (H) of the corallum, number of corallites in the colony (NC), number of septa in the mother corallite at the center of the colony (NS), minimum distance between centers of central corallite and corallite of the inner ring (C1), minimum distance between corallite centers of the outer ring (C2), septal density (DS) and trabecular density (DT). The principal components analysis reveals that most of the variation is explained by 'size' related characters (D and H) while corallite density (NC and C1) and septal structures (DS and DT) contribute to the second and third principal component axes, respectively. The microarchitecture and distribution of characters observed in the Kachchh Dimorpharaea require a re-evaluation of familial-specific concepts and suggest that the population belongs to a single species, Dimorpharaea stellans Gregory, 1900, rather than four nominal species (D: stellans, D. distincta, D. continua and D. orbica) as has been assumed.