Paleoecology and Systematics of the Echinoderm Faunas of the Middle Ordovician Platteville and Lower Galena Groups of North-central Illinois and South-central Wisconsin

Résumé du livre

[An] unusually large, diverse and well-preserved echinoderm fauna has been discovered in the Middle Ordovician Platteville and lower Galena rocks of north-central Illinois and south-central Wisconsin. The echinoderms are associated with an extensive fauna representing a number of invertebrate phyla as well as a variety of multicellular algae. Studies of these organisms and their enclosing sediment suggest that they largely represent the accumulation of recurrent communities in place. Recent advances in the understanding of the genesis of carbonate sediments and recognition of ancient communities provide a good opportunity to analyze this early echinoderm fauna in terms of paleoecology and evolution. The purpose of this investigation is to determine the probable depositional environments, make a preliminary survey of the composition and structure of the communities, and to systematically describe the echinoderms.