LATE CAMBRIAN CONULARIIDS FROM WISCONSIN AND MINNESOTA

Several localities within the heterolithic facies of the St. Lawrence Formation (Upper Cambrian) of Wisconsin and Minnesota yield specimens with phosphatic exoskeletons, quadrate cross sections composed of four equidimensional faces each bearing a midline, and possible holdfast attachment during lif...

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Bibliographic Details
Published in:Journal of paleontology 2000-09, Vol.74 (5), p.828-838
Main Authors: HUGHES, NIGEL C, GUNDERSON, GERALD O, WEEDON, MICHAEL J
Format: Article
Language:English
Subjects:
Baccaconularia
Baccaconularia meyeri
Baccaconularia robinsoni
Biological taxonomies
Cambrian
Cnidaria
Coelenterata
Conularia
Conularia cambria
Conulariida
Dane County Wisconsin
Exoskeletons
Fossils
Geological facies
Geology
Holotypes
Invertebrata
invertebrate
Materials preservation
Minnesota
Mississippi Valley
new taxa
Paleontology
Paleozoic
revision
Saint Lawrence Formation
Sauk County Wisconsin
Scyphozoa
Skeleton
Taxa
Trempealeau County Wisconsin
United States
Upper Cambrian
Upper Mississippi Valley
Wabasha County Minnesota
Wisconsin
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Description
Summary:Several localities within the heterolithic facies of the St. Lawrence Formation (Upper Cambrian) of Wisconsin and Minnesota yield specimens with phosphatic exoskeletons, quadrate cross sections composed of four equidimensional faces each bearing a midline, and possible holdfast attachment during life. These specimens are here referred to the order Conulariida, class Scyphozoa. Their fine, tuberculate surface ornament and serially invaginated midline structure serve to define a new genus, Baccaconularia, to which two new species, B. robinsoni and B. meyeri, are assigned. Conularia cambria Walcott 1890, also from the Cambrian of the northern Mississippi Valley and long dismissed as a misidentified trilobite fragment, is illustrated photographically for the first time. This species occurs in rocks stratigraphically beneath the St. Lawrence Formation. Specimens assigned to this species by Walcott are conulariids, but lack features now considered diagnostic of either Conularia or Baccaconularia. Walcott's material is insufficient to permit 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 known from the Lower Ordovician onwards, and smaller fossils with conulariid affinities known only from Lower Cambrian rocks.
ISSN:0022-3360
1937-2337
DOI:10.1666/0022-3360(2000)074<0828:LCCFWA>2.0.CO;2