Diagnostic Features:
Medium to large in size (0.15-21.1 m), the body ranges from subcylindrical to greatly flattened and disklike, and has five to seven gill slits and gill arches, which open separately to the outside, without an operculum. Dorsal fins and spines, when present, are not erectile but rigid. A spiracle, a remanent of the hyoid gill slit, is present or absent. The upperjaw (palatoquadrate) is not fused to the cranium, and jaw suspension is amphistylic or hyostylic. The notochord, in most cases, is segmentally constricted by vertebral centra which are usually well developed; the trunk vertebrae generally have short ribs. Teeth are numerous. The body generally is covered with small placoid scales. A stomach is present. The urogenital pores and anus open into the cloaca. Males have pelvic claspers, but lack prepelvic claspers (tenacula) or a frontal clasper on the head.
This is the larger of the 2 chondrichthian subclasses; all Iiving species are grouped in the cohort Euselachii, subcohort Neoselachii, in 4 superorders. The 4 superorders of this subcohort are the Squalomorphii, Batoidea, Squatinomorphii, and Galeomorphii.