ECOLOGY AND TAPHONOMY OF SILURIAN CONULARIIDS FROM THE WAUKESHA LAGERSTÄTTE, WISCONSIN

The Silurian (late Telychian) Brandon Bridge Formation, Wisconsin, USA, hosts a diverse biota of arthropods, annelids, graptolites, brachiopods, corals, sponges, and algae, some of which exhibit exceptional soft-bodied preservation. Whilst many of the rarer, enigmatic constituents of the Waukesha Konservat-Lagerstätte have received taxonomic and taphonomic study, some of the more common taxa remain poorly documented. In order to provide a more complete account of the ecology and diversity of this assemblage, our study is focused on the taxonomic description of a prolific Waukesha faunal element—the conulariids. Specimens (n=21) borrowed from the University of Wisconsin Geology Museum, Madison, USA, were examined using a combination of light microscopy, scanning electron microscopy, and energy dispersive spectrometry (SEM-EDS) to assist in the classification of these taxa. This low diversity conulariid assemblage is characterized by two species, including Conularia niagarensis Hall, 1852 and Metaconularia manni Roy, 1935. Specimens of both taxa often exhibit holdfasts of an encrusting epibiont, Sphenothallus, which is known to co-occur with conulariids throughout the Paleozoic. While body fossils of Sphenothallus are recorded from the Waukesha, only the holdfasts are ever found in direct association with conulariid specimens. Preliminary statistical analyses on our limited samples suggest a kleptoparasitic relationship between Sphenothallus and the host conulariids, though we cannot dismiss a commensal relationship. Conulariids display some variation in preservation between species owing to the original level of biomineralization of the shell. Results of EDS analyses reveal that the shell material is predominantly composed of francolite (calcium phosphate) that experienced partial post-burial dissolution, resulting in the uncommon two-dimensional preservation of these specimens. Despite the common exceptional preservation of Waukesha Lagerstätte specimens, conulariids rarely preserve soft-bodied material. This may be a result of the poor preservation of diploblastic tissue in anoxic conditions that prevail in most Lagerstätten.