Helicoplacoidea: A New Class of Echinoderms

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Science  17 May 1963:
Vol. 140, Issue 3568, pp. 820-822
DOI: 10.1126/science.140.3568.820


A fusiform, spirally coiled and pleated, free-living, heavily placate echinoderm with an expansible test has been discovered in the Lower Cambrian Olenellus zone of California. It is characterized by 10 "interambulacral" areas, a single principal endothecal ambulacrum with a short branch, and oral and apical regions at opposite poles. A new class, the Helicoplacoidea is proposed for the new genus Helicoplacus, with two new species, H. gilberti (type species) and H. curtisi.