Two New Pacific Ocean Species of Hyocrinid Crinoids (Echinodermata), with Comments on Presumed Giant-Dwarf Gradients Related to Seamounts and Abyssal Plains

Abstract

Hyocrinus foelli, n. sp. is a small hyocrinid sea lily from the abyssal ferromanganese nodule fields of the North Pacific Ocean. Hyocrinus giganteus, n. sp. is a very large hyocrinid from Horizon Seamount in the eastern Pacific that shows close affinities to H. cyanae from the western Pacific, off New Caledonia. A possible giant-dwarf heterochronic gradient, related to scarcity of food supply in abyssal plains and its abundance in seamount environments, is discussed.