A small class of primitive echinoderms (subphylum Echinozoa) known from the single species Camptostroma roddyi based on about 200 specimens from the Early Cambrian (Bonnia-Olenellus Zone) in southeastern Pennsylvania. Camptostroma was originally described as a hydrozoan or jellyfish, but it was recognized as an echinoderm and the new class Camptostromatoidea was set up for it. Camptostroma has been reinterpreted as an early edrioasteroid, and as a “stem echinoderm” ancestral to several other groups including edrioasteroids. Because of Camptostroma's puzzling morphology, different reconstructions of it have been made (see illus.). It has a conical or domal theca or body with a nearly circular outline, divided into a pleated lower theca with larger and smaller overlapping plates, and a domed upper theca made up of large plates with pores on their margins surrounded by numerous smaller plates. The upper theca bears five straight to curved ambulacra protected by numerous cover plates and radiating from the central mouth, and a small anal pyramid at one edge. Camptostroma probably had the lower theca either embedded in the soft sediment or attached to objects lying on the sea floor, making it a stationary or attached, low-level suspension feeder using tube feet in the ambulacra to capture small food particles drifting by the theca. The unusual thecal plating is the main feature separating Camptostroma from later Edrioasteroidea, which it otherwise resembles, but this genus may also have been ancestral to other classes such as the Eocrinoidea.