COMMENSUAL ENDOLITHIC BORING TRACES ON SPIRIFERID HOSTS FROM THE MIDDLE DEVONIAN OF CENTRAL NEW YORK

Commensal endolithic borings are relatively rare during the Devonian and have been largely attributed to sponge, worm and bryozoan dwelling activity. Investigation of more than 100 well-preserved spirifierid brachiopod hosts from the Middle Devonian of central New York reveals at least four ichnospecies and associated bioerosion textures belonging to Clionolithes, Clionoides and Specus suggesting such traces are more common than previously thought. The taxonomy of Devonian sponge and worm ichnofossils remains problematic due to the scarcity of well-preserved diagnostic morphological features differentiating the boring traces. The most common sponge-traces include at least two small radiating forms infesting Athrys hosts that correspond closely to Clionolithes radicans originally described by John Clarke in the early 1900’s and subsequently referred to Nododerdrina and Ramodendrina. Associated with Clionolithes are larger, U-shaped, ribbed tubes which we attribute to worm dwelling traces of Specus. Although Specus and Clionolithes co-occur in close proximity on the same host, they exhibit no apparent site preference on valve surface. The re-examination of Clarke's types together with recently collected specimens suggest the need for a new Clionoides ichnospecies distinguished by large cylindrical tubes parallel to the shell surface with small perpendicular cones extending from the larger tubes. This larger form. also attributed to sponge activity, penetrates near the umbo of host brachiopod and extends radially towards the commissure and is associated with a unique pitted texture covering host shell surface. Taken together, these endolithic borings provide for a better understanding of sponge and worm ichnofossil richness during the Middle Devonian.