Borings on Belemnoid Rostra from Utatur Group of Upper Cretaceous Rocks of Trichinopoly District, Tamil Nadu

The activity of algae, fungi, sponges, bryozoa and barnacles on the belemnoid rostra from clays of the Utatur Group in the form of micro borings are described. The sponge and bryozoan borings are represented by Clionoides Fenton & Fenton and Talpina Hagenow respectively; while, barnacle borings are represented by ichnogenus Brachyzapfes Codez and De Saint-Seine. The algal borings are assigned to ichnogenus Calcideletrix Haentzschel. Ichnogenera Nygmites Haentzschel and Radiarites ichnogen. nov. are the borings of fungi. Ichnogenus Cylindrocavites Ichnogen nov. is erected to accommodate circular borings of unknown affinities.

The present study shows that the borers and the belemnoids belonged to the same biocoenose and indicate littoral to shallow sublittoral depths of well aerated, slightly turbulent but clear marine waters.