LATEST CAMBRIAN CORNUTES (ECHINODERMATA: STYLOPHORA) FROM THE TAEBAEKSAN BASIN, KOREA

Abstract

The oldest echinoderms and first cornute stylophorans ever reported from Korea are described, based on more than 40 specimens collected from the Late Cambrian of the Taebaeksan Basin. New material doubles the number of stylophorans described from Asia and the number of specimens of Late Cambrian stylophorans recorded throughout the world. Three different cornutes are identified: Sokkaejaecystis serrata n. gen. and sp. and two genus and species indeterminate forms A and B. Sokkaejaecystis serrata and indeterminate form B are assigned to the Chauvelicystinae, while the systematic position of indeterminate form A within cornutes is difficult to assess. This new material suggests paleobiogeographic connections between echinoderm faunas from Korea, western North America (Wyoming), and western Europe (Montagne Noire, Shropshire). A cladistic analysis of selected cothurnocystids shows that Sokkaejaecystis n. gen. is closely related to Prochauvelicystis and the sister group of a clade uniting Ampelocarpus with Lyricocarpus. The analysis also confirms the placement of Milonicystis within the Chauvelicystinae and questions the monophyly of the genus Chauvelicystis. CHINODERMS ARE extremely rare fossils in the Late Cambrian rocks throughout the world. In this study, we report the old- est echinoderm remains (latest Cambrian) ever discovered in Ko- rea, based on new materials from the Tongjom Formation of the Taebaeksan Basin. This material comprises more than 40 speci- mens of cornute stylophorans, with numerous isolated plates and columnals of a Macrocystella-like rhombiferan blastozoan. This study focuses on the description of three cornute stylophorans, Sokkaejaecystis serrata n. gen. and sp., and genus and species indeterminate forms A and B. The new specimens have doubled the number of stylophorans reported from Asia, formerly includ- ing only the two mitrates Anatifopsis cocaban Kobayashi, 1960 and A. truncata Kobayashi, 1960 from the Early Ordovician of Korea (Kobayashi, 1960; Choi and Kim, 1989; Dominguez and Gutierrez, 1990) and the cornuteMongolocarpos minzhiniRozh-