Article: Early Cretaceous Isocrinus from northeast Japan
Two species otlsocrinus, one of which is new (Isocrinus (Chladocrinus) hanaii sp. nov.), are described from the upper Aptian of the Miyako Group, Northeast Japan. The skeletons of I. (C.) hanaii are preserved intact at several localities, so it is presumed that they were rapidly buried either alive or shortly after death, the animals having lived on a sandy bottom in agitated water. In contrast to the relatively deep-water occurrence of modern isocrinids (mostly 200-1000 m), those from Miyako lived in shallow water, indicating that certain stalked crinoids persisted at shallow depths until mid-Cretaceous times. They were among the last isocrinids to have lived in an almost predator-free environment. Soon afterwards, a diversification of predatory teleostean fish was reflected in the contemporaneous appearance of new types of isocrinids.