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Some Molluscan Problematica from the Upper Cambrian. Lower Ordovician of the Ozark Uplift

Bruce L. Stinchcomb and Guy Darrough
Journal of Paleontology
Vol. 69, No. 1 (Jan., 1995), pp. 52-65
Published by: Paleontological Society
Stable URL: http://www.jstor.org/stable/1306279
Page Count: 14
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Since scans are not currently available to screen readers, please contact JSTOR User Support for access. We'll provide a PDF copy for your screen reader.
Some Molluscan Problematica from the Upper Cambrian. Lower Ordovician of the Ozark Uplift
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Abstract

The mollusk Hemithecella, which occurs abundantly both above and below the Cambrian--Ordovician boundary in the Ozark region of Missouri, is discussed and compared with Matthevia and with the polyplacophoran order Paleoloricata and found to be distinctly different. Based upon the presence of monoplacophoran-like multiple muscle scars and asymmetrical valves, Hemithecella and related forms described here are considered to be molluscan problematica. Hemithecellids are mollusks; however, their affinity to other classes is unclear although structural similarities to the Monoplacophora are noted. The new order Hemithecellitina is proposed. It contains two new families, the Hemithecellidae and the Robustidae. Three new genera, Conodia, Robustum, and Elongata, and nine new species are proposed: Conodia levicosta, C. acuminata, Robustum nodum, R. phallarium, Elongata perplexa, Hemithecella elongata, H. abrupta, H. quinquelites, and H. eminensis.

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