Crinoids from the Silurian of Western Ohio and Indiana

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The Ohio State University

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A large section of the stratigraphic column of the Great Lakes Area is composed of carbonate rock from the Silurian Period (ca. 443-419 Ma). This limestone, which has been highly dolomitized, formed in association with an ancient reef system that was present in the epicontinental seas that prevailed during this time. The rock has been thoroughly studied for both economic and academic purposes. Silurian dolomites are used for industrial purposes, and they are a key oil producer. Study of these carbonate rock has also revealed much about the nature of ancient reef systems. However, there is still much to learn about these reef systems. Of particular interest is the biota that helped to form the reefs. Among the least understood Silurian reef contributors are the echinoderms, in particular the crinoids. Little research has been done on Silurian reef crinoids; the last major work was in 1900. This is in part due to the high dolomitization of the fossils that makes identification of these species more difficult. To develop a better understanding of these species, a systematic study is being undertaken to identify several specimens from five different quarries in the western Ohio and Indiana. The study of these crinoids has led to further advances in the understanding of Silurian reefs worldwide. Understanding these crinoids provides further insight into the phylogenetic history of the crinoid class, allowing also for a greater understanding of echinoderm evolution. The identification of these Silurian crinoids also aids in understanding of the organisms and the processes by which these reefs formed. There is much to be discovered yet in the Silurian reefs of the Great Lakes Area, and the identification of these crinoid species is a step toward more complete understanding.



Systematics, Crinoids, Silurian, Ohio