ABSTRACT
Lanterns of fossil irregular echinoids of the orders Holectypoida (sensu Wagner & Durham, 1966) and Pygasteroida Durham & Melville, 1957, are regarded as a possibly stirodont type.
Echinoneus cyclostomus Leske is a Recent species of Holectypoida which has a lantern during its juvenile life. The only Known specimens possessing a lantern show pyramids lacking processi supra alveolares and epiphyses with short disc-like demi-arcs. The teeth bear a thick keel, this last feature makes the teeth slightly different from those of Holectypus depressus CLeske) and Pygaster trigeri Cotteau. The structures of the skeletal elements in the lantern of E. cyclostomus indicate that it may be an early irregular echinoid with upright lantern
