The examination of faunas characterized by unusual preservation and/or occurrence in unusual environments can provide much paleoecological information. In this vein, PIs will investigate the paleoecology of three exquisitely preserved and diverse echinoderm faunas from the Middle Ordovician of Iowa ans Minnesota. The lithologies and regional stratigraphy indicate that the animals swelled on a shallow, equatorial epicontinental shelf in waters 40 to 50 m deep. The communities are dominated by suspension-feeding echinoderms. Catastrophic burial resulted in the preservation of many complete adult and some juvenile ecinoderms. Consequently, PIs will determine the elevations relative to the substrate at which the individuals lived, estimate the sizes of food particles taken and infer their methods of food capture by extrapolating from Recent crinoids and other echinoderms and by applying filtration theory. The material encourages reconstruction of ecological structure, both in the context of adults and ontogenetic sequences. Preliminary data demonstrate that the tiering levels and food size selection of Middle Ordovician echinoderms were as complicated as those of the crinoid dominated faunas of the Mississippian. However, typical Ordovician forms utilized somewhat different elevations above the substrate than in the later Mississippian occurrences. Ontogeny, survivorship and distribution patterns will be examined for the abundant taxa within and between different living and taphonomic settings. Inasmuch as most taxa are new, the fauna will be described and its phylogenetic affinities ascertained.
