Problematic Stromatocystites Early Starfish Relative

This superb Echinoderm is a member of the Edrioasteroidea known as Strmatocystites pentangularis. This group of starfish relatives derives its name from the Greek for seated star, and describes their sessile nature. Unlike the highly mobile starfish, Edrioasteroids were attached to a substrate by a short thick stalk covered with plates. The ambulacra (radiating feeding grooves) were covered by large rooflike plates which were capable of being raised, and were arrayed in a characteristic spiral pattern. These echinoderms arose during the Lower Cambrian, and survived until the Middle Pennsylvanian. This one is from the base of that radiation, and some prefer to use the term “edrioasteroid-like” taxon to describe it, although they are indeed among the earliest of echinoderms that lived from the Ediacaran to the Carboniferous periods of geologic time, about 600-300 million years ago.