Paper No. 36
Presentation Time: 9:00 AM-6:00 PM
COMMENSUAL BORINGS FROM THE MIDDLE DEVONIAN OF CENTRAL NEW YORK AND THE STATUS OF PALEOSABELLA CLARKE 1921, CLIONOIDES FENTON AND FENTON 1932 AND VERMIFORICHNIS CAMERON 1969
Commensal endolithic borings are relatively rare during the Devonian and have been largely attributed to sponge, worm and bryozoan dwelling activity. The taxonomy of many of these ichnofossils remain problematic due to the scarcity of well-preserved diagnostic morphological features differentiating the boring traces. Through the investigation of endoliths infesting more than 100 well-preserved spirifierid brachiopod hosts from the Middle Devonian of central New York, four ichnospecies and associated bioerosion textures are revealed. The most common sponge traces include the two small rosette forms of Clionolithes nodosa (Vogel et al) and Clionolithes cervicornis (Vogel et al.) which closely resemble Clionolithes radicans Clarke and formally assigned to as Nododerdrina and Ramodendrina. Frequently co-occurring with Clionolithes are small, U-shaped tubes which we attribute to worm dwelling traces of a new and unnamed ichnogenus and ichnospecies. The new combination of Clionoides clarki (Cameron) describes large cylindrical tubes that are parallel to the shell surface with small perpendicular cones extending from the larger tubes. These larger forms, also attributed to sponge activity, penetrate near the umbo of host brachiopod and extend radially towards the commissure. They are also associated with a unique pitted texture covering host shell surface and occasionally co-occurs with the encrusting bryozoan Paleschara incrustans Hall. A new combination for these forms is needed because of its long and confusing nomenclatural history. Paleosabella prisca (McCoy) was originally used by Clarke to describe similar borings from the Devonian of New York, and have been placed by Cameron into Vermiformichnus clarki. Examination of Clarke’s and Cameron’s type specimens and those of this study reveal similar tube morphology and additional structures (pitting and cone extensions) that suggest Vermiformichnus is similar to Clionoides and should be considered synonyms.