Paleoecology of Some Exceptional Echinoderm Faunas: Middle Ordovician of the Mid-Continent

以异常保存和/或在异常环境中出现为特征的动物群的研究可以提供许多古生态信息。在这种情况下，PI将研究来自爱荷华州和明尼苏达州中奥陶世的三个保存精致和多样化的棘皮动物动物群的古生态。岩性和区域地层学表明，这些动物在40至50米深的浅水赤道陆缘陆架上膨胀。群落以悬浮进食的棘皮动物为主。灾难性的埋葬导致许多完整的成体和一些幼年外胚层被保存下来。因此，PI将确定相对于个体所在底物的海拔高度，估计摄取的食物颗粒的大小，并通过从最近的海鞘动物和其他棘皮动物推断并应用过滤理论来推断它们捕获食物的方法。该材料鼓励在成人和个体发育序列的背景下重建生态结构。初步数据表明，中奥陶世棘皮动物的分层水平和食物大小的选择与密西西比河流域以海鞘为主的动物群一样复杂。然而，与密西西比晚期发生的情况相比，典型的奥陶纪形式使用的基岩上方的海拔略有不同。将对不同生物和蚕茧环境内和之间丰富的类群的个体发育、生存和分布模式进行研究。由于大多数分类群都是新的，因此将对动物群进行描述，并确定其系统发育亲缘关系。

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.