Anomalocystitid Mitrates (Stylophora-Echinodermata) from the Champlainian (Middle Ordovician) Guttenberg Formation of the Upper Mississippi Valley Region

Two new mitrate stylophoran "carpoids," Ateleocystites guttenbergensis n. sp. and Willmanocystis denticulatus n. gen. and n. sp., have been discovered in the Champlainian (middle Ordovician) Guttenberg Formation of the Upper Mississippi Valley Region. The family Anomalocystitidae, to which both new mitrates are assigned, is partitioned into two subfamilies: the Placocystitinae that have 2 adaulacophorals and a placocystid plate (A. guttenbergensis n. sp. belongs here) and the Enoplourinae that have 3 adaulacophorals and lack a placocystid plate (Willmanocystis belongs here). The problem most critical to the understanding of stylophoran phylogeny and functional morphology is that neither the mouth nor anus can be identified definitely. The single main thecal orifice that is recognized in all species has been variously interpreted as a mouth, an anus, or a mouth-anus combination. Based on a review of the various interpretations we prefer to consider the main thecal orifice as an opening for all intake and excretion.