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Silurian sponge spicules from the Racine Formation, Wisconsin

Published online by Cambridge University Press:  20 May 2016

Rodney Watkins  and
P. J. Coorough
Rodney Watkins
Affiliation:
Department of Geology, Milwaukee Public Museum, 800 West Wells Street, Milwaukee, WI 53233, USA
P. J. Coorough
Affiliation:
Department of Geology, Milwaukee Public Museum, 800 West Wells Street, Milwaukee, WI 53233, USA
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Abstract

The Silurian (Wenlockian) Racine Formation of Milwaukee, Wisconsin has yielded 22 types of siliceous and silicified sponge spicules. The spicules occur in bioturbated dolomite mudstone, and they are part of a high-diversity community of small crinozoans, brachiopods, and other taxa. Siliceous desmas of the order Lithistida comprise 79 percent of recovered spicules. Siliceous triaxons of the class Hexactinellida and silicified sexiradiates of the class Heteractinida each comprise 7 percent of spicules. Eleven additional types of siliceous spicules of uncertain taxonomic affinity form 7 percent of the assemblage. No complete sponge skeletons have been observed, probably because of slow deposition and high bioturbation. The Racine spicule assemblage resembles sponge faunas of Silurian offshore deposits in the Canadian Arctic and Great Basin, which suggests moderate bathymetric relief in the Michigan Basin during Wenlockian times.

Type
Research Article
Information
Journal of Paleontology , Volume 71 , Issue 2 , March 1997 , pp. 208 - 214
Copyright
Copyright © The Paleontological Society 

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