Late Cambrian conulariids from Wisconsin and Minnesota

Several localities within the heterolithic facies of the St. Lawrence Forma tion (Upper Cambrian) of Wisconsin and Minnesota yield specimens with phosp hatic exoskeletons, quadrate cross sections composed of four equidimensiona l faces each bearing a midline, and possible holdfast attachment during lif e. These specimens are here referred to the order Conulariida, class Scypho zoa. Their fine, tuberculate surface ornament and serially invaginated midl ine: structure serve to define a new genus, Baccaconularia, to which two ne w species, B. robinsoni and B. meyeri, are assigned. Conularia cambria Walc ott 1890, also from the Cambrian of the northern Mississippi Valley and lon g dismissed as a misidentified trilobite fragment, is illustrated photograp hically for the first time. This species occurs in rocks stratigraphically beneath the St. Lawrence Formation. Specimens assigned to this species by W alcott are conulariids, but lack features now considered diagnostic of eith er Conularia or Baccaconularia. Walcott's material is insufficient to permi t detailed taxonomic evaluation, and we isolate this name to this material, pending the collection of additional, better preserved specimens. Together , Baccaconularia and Conularia cambria contain the oldest large conulariids , and these narrow a stratigraphic gap between other large conulariids know n from the Lower Ordovician onwards, and smaller fossils with conulariid af finities known only from Lower Cambrian rocks.