Tremadocian stylophoran echinoderms from the Taebaeksan Basin, Korea

Abundant isolated elements of cornute and mitrate stylophorans were recovered from the upper Tremadocian Tumugol Formation in the Taebaeksan Basin, Korea. Cornute skeletal elements comprise a diverse assemblage of marginals and brachials of cothurnocystid affinities, suggesting the presence of no fewer than four different species. Mitrate remains include numerous isolated adorals, marginals, and aulacophoral plates with typical peltocystidan morphologies. Two adorals are identified as Anatifopsis sp., while all the others are attributable to A. cocaban. However, the two previously documented peltocystidans of Korea, A. cocaban and A. truncata, are sufficiently distinct from other Anatifopsis species to warrant assignment to a new genus, TAEBAEKOCYSTIS. Cladistic analyses suggest that Lagynocystida is the sister group of the clade uniting peltocystidans and mitrocystitidans and that the adorals of Taebaekocystis n. gen. and associated isolated peltocystidan elements possibly account for several different types of peltocystidans, intermediate in morphology between Peltocystidae and Kirkocystidae.