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

对具有不寻常特征的动物群的研究 保存和/或出现在不寻常的环境中， 提供了大量的古生态信息。 在这种情况下，PI将 调查三个保存完好的古生态， 爱荷华州安中奥陶世不同棘皮动物群 明尼苏达 岩性和区域地层表明 这些动物生长在一个浅的赤道陆缘带， 在40到50米深的沃茨中的陆棚。 这些社区被 悬浮进食的棘皮动物。 灾难性的埋葬 在保存许多完整的成年和一些少年 棘皮动物 因此，PI将决定海拔 相对于个体生活的基底， 估计食物颗粒的大小，并推断它们的 从最近的海百合外推食物捕获方法， 其他棘皮动物和应用过滤理论。 的 物质鼓励生态结构的重建， 在成年人和个体发育序列的背景下。 初步 数据表明，分层水平和食物大小选择， 中奥陶世棘皮动物的复杂程度 密西西比纪以海百合为主的动物群。 然而，在这方面， 典型的奥陶纪形态利用了稍微不同的海拔高度 比密西西比纪晚期的更高。 个体发育，生存和分布模式将进行检查 对于丰富的类群内部和之间的不同生活， 埋藏环境 由于大多数分类群是新的， 将被描述，并确定其系统发育的亲和力。

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.