Trilobites of the Upper Cambrian Ptychaspid biomere, Wilberns Formation, central Texas

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Trilobites of the Upper Cambrian Ptychaspid biomere, Wilberns Formation, central Texas

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dc.contributor.advisor Bell, William Charles, 1911-
dc.creator Longacre, Susan Ann
dc.date.accessioned 2011-06-24T22:03:10Z
dc.date.available 2011-06-24T22:03:10Z
dc.date.created 1968-06
dc.date.issued 2011-06-24
dc.identifier.uri http://hdl.handle.net/2152/11967
dc.description.abstract Trilobites collected during the past twenty years from the Morgan Creek, Point Peak, and San Saba members of the Wilberns Formation constitute the material basis for this paleontologic and statistical investigation. Eighty-nine species assigned to forty-five genera belong to zones of the upper Franconian and Trempealeauan Stages of the Upper Cambrian Croixan Series. New zonal names are proposed in the interest of a regionally applicable nomenclature. Although none of the zonal nomenclature is identical to that of the Cambrian Correlation Chart, the four zones recognized in central Texas are equivalent to the eight highest zones of the Chart. Stratigraphically lowest is the Franconian Taenicephalus zone, with a locally recognized Parabolinoides subzone at its base; this is equivalent to the Conaspis zone of the Correlation Chart. The Franconian Idahoia zone, with a locally recognized Idahoia lirae subzone at its base, is equivalent to the Ptychaspis subzone of the Ptychaspis-Prosaukia zone of the Correlation Chart. The sparsely fossiliferous Ellipsocephaloides zone corresponds to the Prosaukia subzone of the Ptychaspis-Prosaukia zone of the Chart. Almost two-thirds of the trilobite species occur in the Trempealeauan Saukia zone, which corresponds to the five highest zones of the Correlation Chart; local subzones, in ascending order, are the Saukiella pyrene subzone, the Saukiella junia subzone, the Saukiella serotina subzone, and the Corbinia apopsis subzone. The succession of ptychoparioid trilobite faunas contained within these zones make up the Ptychaspid biomere. The base of the biomere is at the base of the Taenicephalus zone; the top coincides with the lowest occurrence of the Ordovician trilobite fauna. Trilobite families that characterize the Ptychaspid biomere are the Ptychaspididae and the Parabolinoididae. Regression analyses of range data for all Saukia-zone taxa were used to compile a quantitative range chart. Differences between the quantitative chart and my intuitive range chart were not significant. Systematic descriptions include new species of Conaspis, Idiomesus, Euptychaspis, Keithiella, Saukiella, Prosaukia, Calvinella, and Westonaspis?; and one new variety of Orygmaspis.
dc.format.medium electronic
dc.language.iso eng
dc.rights Copyright © is held by the author. Presentation of this material on the Libraries' web site by University Libraries, The University of Texas at Austin was made possible under a limited license grant from the author who has retained all copyrights in the works.
dc.subject Paleontology--Cambrian
dc.subject Trilobites--Texas
dc.subject Paleontology--Texas
dc.title Trilobites of the Upper Cambrian Ptychaspid biomere, Wilberns Formation, central Texas
dc.description.department Geological Sciences
dc.type.genre Thesis
dc.type.material text
thesis.degree.department Geological Sciences
thesis.degree.discipline Geological Sciences
thesis.degree.grantor The University of Texas at Austin
thesis.degree.level Doctoral
thesis.degree.name Doctor of Philosophy

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