Strut always composed of marginal plates. Few to multiple thecal spines serve as anchoring structures in most species.
Respiratory structures range from simple sutural pores to complex cothurnopores and lamellipores.
Aulacophore with simple stylocone and tall, loosely articulated cover plates over the food groove. Respiratory structures, rare, sutural pores. M4 in direct contact lack a CS plate, commonly have one spine, and a subanal plate. In some cases, distal marginal plate designations in the literature are erroneous but correctable when positions of septum and anal structures are considered. Traditional familial groupings are not recognizable.