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Trilobites of the Gilmore City Limestone (Mississippian) of Iowa

Published online by Cambridge University Press:  19 May 2016

David K. Brezinski
David K. Brezinski*
Affiliation:
Maryland Geological Survey, 2300 St. Paul Street, Baltimore 21218
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Abstract

Four trilobite species are present in the Gilmore City Limestone (Kinderhookian–Osagean) of Humbolt County, Iowa. The most common trilobite taxa, Perexigupyge hodgesi n. gen. and sp. and Perexigupyge gerki n. gen. and sp., make up the greatest percentage of the trilobite population. Two other species are known from fragmentary cranidia and are assigned to the genera Richterella and Proetides. Prior to the description of these forms, the only trilobite previously described or illustrated from the Gilmore City Limestone was a cranidium of Proetides insignis (Winchell) from the type area.

The Gilmore City Limestone in Humbolt County, Iowa, represents deposits associated with an oölitic sand-shoal environment, including washover-lobe and back-shoal deposits. Morphologic attributes exhibited by the Gilmore City Limestone trilobites, such as low relief and vaulting to the exoskeleton and subdued surface ornamentation, may have been adaptations that enabled them to inhabit current-swept shoal environments. Conversely, coarsely tuberculate forms may have used the tubercules as a mimic of the surrounding coarse-grained sediment or to strengthen the exoskeleton.

Type
Research Article
Information
Journal of Paleontology , Volume 62 , Issue 2 , March 1988 , pp. 241 - 245
Copyright
Copyright © The Paleontological Society 

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