Superorder Galeomorphii
Diagnostic Features:
Very small to gigantic (24 cm to over 12.1 m in maximum total length) sharks with a subcylindrical or moderately depressed body. Usually two dorsal fins are present (a single dorsal fin in I genus of the Scyliorhinidae), with or (usually) without fin spines; an anal fin is present; the caudal fin is heterocercal to diphycercal. Five external gill openings are present on the sides of the head, with five gill arches; the spiracles are well developed to absent. The mouth is subterminal to almost terminal. The eyes are with (Carcharhiniformes) or without nictitating lower eyelids. The cloaca is confluent with the inner margins of the pelvic fins. The cranium has the rostrum absent in the Heterodontiformes. When present, the rostrum is not trough-shaped, with a single rodlike medial rostral cartilage (Orectolobiformes) or a medial and two lateral rostral cartilages forming a tripod that encloses the precerebral cavity, with strong suborbital shelves, with no basal angle, with the preorbital wall complete orin complete and postorbital walls incomplete, with the supraorbital crests primitively strong but secondarily lost in some groups, and with the otic capsules relatively short in most groups except some Lamniformes and Carcharhinidae. and without lateral commissures. The upper jaw (palatoquadrate) has an anterior orbital articulation with the nasal capsules, basal plate, and suborbital shelves of the cranium. The pectoral fin skeleton has a small, laterally positioned propterygium. a long me tapterygium, and a short metapterygial axis. This superorder includes about 246 to 258 species in 68 genera, 23 families, and 4 orders (Heterodontiformes, Orectolobiformes, Lamniformes, and Carcharhiniformes). The galeomorphs are presently the dominant group of sharks, found in all habitats in which sharks occur, with the apparent exception of the Arctic seas, which are inhabited by the squalomorph sleeper sharks (Squalidae genus Somniosus).