Skip to main content Accessibility help

Silurian sponge spicules from the Racine Formation, Wisconsin

  • Rodney Watkins (a1) and P. J. Coorough (a1)


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.



Hide All
Bengston, S. 1986. Siliceous microfossils from the Upper Cambrian of Queensland. Alcheringa, 10:195216.
Boucot, A. J. 1975. Evolution and Extinction Rate Controls. Elsevier, Amsterdam, 427 p.
Brett, C. E., Boucot, A. J., and Jones, B. 1993. Absolute depths of Silurian benthic assemblages. Lethaia, 26:2540.
de Freitas, T. A. 1991. Ludlow (Silurian) lithistid and hexactinellid sponges, Cape Phillips Formation, Canadian Arctic. Canadian Journal of Earth Sciences, 28:20422061.
Dong, X. P., and Knoll, A. H. 1996. Middle and late Cambrian sponge spicules from Hunan, China. Journal of Paleontology, 70:173184.
Kuglitsch, J. J. 1994. Conodont biostratigraphy of the Silurian Waukesha, Racine and Engadine formations, eastern Wisconsin. Geological Society of America Abstracts with Programs, 26(4):49.
Mehl, D., Rigby, J. K., and Holmes, S. B. 1993. Hexactinellid sponges from the Silurian–Devonian Roberts Mountains Formation in Nevada and hypotheses of hexactine-stauractine origin. Brigham Young University Geology Studies, 39:101124.
Mikulic, D. G., and Kluessendorf, J. 1988. Subsurface stratigraphic relationships of the Upper Silurian and Devonian rock of Milwaukee County, Wisconsin. Geoscience Wisconsin, 12:123.
Nitecki, M. H., and Dapples, C. C. 1975. Silurian Ischadites tenuis n.sp. (Receptaculitids) from Indiana. Fieldiana Geology, 35:1120.
Rigby, J. K. 1983. Fossil Demospongia, p. 1239. In Broadhead, T. W. (ed.), Sponges and Spongiomorphs. University of Tennessee Department of Geological Sciences Studies in Geology 7, Knoxville, Tennessee.
Rigby, J. K. 1995. Sponges as microfossils, p. 117. In Blome, C. D., Whalen, P. M., and Reed, K. M. (eds.), Siliceous Microfossils, Short Courses in Paleontology Number 8. The Paleontological Society, Knoxville, Tennessee.
Rigby, J. K., and Dixon, O. A. 1979. Sponge fauna of the Upper Silurian Read Bay Formation, Somerset Island, District of Franklin, Arctic Caǹada. Journal of Paleontology, 53:587627.
Rigby, J. K., Hannum, C., and Frest, T. J. 1979. Hexactinellid sponges from the Silurian Waldron Shale in southeastern Indiana. Journal of Paleontology, 53:542549.
Rigby, J. K., and Harris, D. A. 1979. A new Silurian sponge fauna from northern British Columbia. Journal of Paleontology, 53:968980.
Rigby, J. K., and Lenz, A. C. 1978. A new Silurian astylospongiid sponge from Baille Hamilton Island, Canadian Arctic Archipelago. Canadian Journal of Earth Sciences, 15:157162.
Rigby, J. K., and Maher, B. J. 1995. Age of the hexactinellid beds of the Roberts Mountains Formation, Snake Mountains, Nevada, and additions to the Silurian sponge fauna. Journal of Paleontology, 69:10201029.
Rigby, J. K., Maher, B. J., and Browne, Q. J. 1991. New hexactinellids from the Siluro–Devonian of the Snake Mountains, Elko County, Nevada, and a new locality for Gabelia . Journal of Paleontology, 65:709714.
Rigby, J. K., and Stuart, R. J. 1988. Fossil sponges from the Siluro–Devonian Roberts Mountains Formation in northeastern Nevada. New Mexico Bureau of Mines and Mineral Resources Memoir 44:129137.
Watkins, R. 1991. Guild structure and tiering in a high-diversity Silurian community, Milwaukee County, Wisconsin. Palaios, 6:465478.
Watkins, R. 1993. The Silurian (Wenlockian) reef fauna of southeastern Wisconsin. Palaios, 8:325338.
Watkins, R., and Kuglitsch, J. J. 1995. A silicified deep-water Silurian fauna from SE Wisconsin. Geological Society of America Abstracts with Programs, 27(3):94.
Webby, B. D., and Trotter, J. 1993. Ordovician sponge spicules from New South Wales, Australia. Journal of Paleontology, 67:2841.
Ziegler, A. M. 1965. Silurian marine communities and their environmental significance. Nature, 207:270272.
Zhang, X., and Pratt, B. R. 1994. New and extraordinary Early Cambrian sponge spicule assemblage from China. Geology, 22:4346.

Related content

Powered by UNSILO

Silurian sponge spicules from the Racine Formation, Wisconsin

  • Rodney Watkins (a1) and P. J. Coorough (a1)


Full text views

Total number of HTML views: 0
Total number of PDF views: 0 *
Loading metrics...

Abstract views

Total abstract views: 0 *
Loading metrics...

* Views captured on Cambridge Core between <date>. This data will be updated every 24 hours.

Usage data cannot currently be displayed.