CHARACTERISTICS:
1) two dorsal fins, each with a strong, smooth spine
2) caudal peduncle with lateral keels and a precaudal pit
3) all five gill slits usually anterior to pectoral-fin base
4) spiracles large
5) anal fin absent
6) nictitating membrane absent
ILLUSTRATED SPECIMEN:
Squalus suckleyi, SIO 08–138, 740 mm TL
SQUALIFORMES : DALATIIDAE—Kitefin Sharks
DIVERSITY: 6 genera, 10 species
REPRESENTATIVE GENERA: Dalatius, Isistius, Squaliolus
DISTRIBUTION: Atlantic, Indian, and Pacific oceans
HABITAT: Marine; tropical to temperate; continental shelf to continental slope, coastal to oceanic, epipelagic to bathypelagic
REMARKS: Kitefin sharks are some of the smallest of all sharks; species in the genus Squaliolus reach maximum sizes of only 22–28 cm TL. These cigar-shaped sharks generally eat small fishes, squids, and crustaceans, but the highly specialized cookiecutter sharks (Isistius spp.) attack much larger prey, removing bite-sized pieces from live marine mammals and large-bodied fishes. Kitefin sharks are yolk-sac viviparous (Musick, 2011; Musick and Ellis, 2005) and probably use their ventral light organs to achieve countershading, decreasing their visual profile from below.
REFERENCES: Compagno, 2005; Compagno, in Carpenter, 2003; Compagno and Niem, in Carpenter and Niem, 1998; Compagno et al., 2005; Musick, 2011; Musick and Ellis, 2005; Shirai, 1992a.
DALATIID CHARACTERISTICS:
1) two dorsal fins, without spines, or with a spine in the first dorsal fin only
2) luminous organs usually present along ventral surface
3) caudal fin with a pronounced notch
4) spiracles large
5) anal fin absent
6) nictitating membrane absent
ILLUSTRATED SPECIMENS:
A) Squaliolus aliae, DE 0508, 117 mm TL
B) Isistius brasiliensis, SIO 69–345, 470 mm TL
INSET: Flank of Oarfish (Regalecus russelii, SIO 13–259) with multiple wounds caused by Isistius brasiliensis.
SQUATINIFORMES : SQUATINIDAE—Angel Sharks
DIVERSITY: 1 family, 1 genus, 22 species
REPRESENTATIVE GENUS: Squatina
DISTRIBUTION: Atlantic, Indian, and Pacific oceans
HABITAT: Marine; tropical to temperate; continental shelf to continental slope, benthic on soft substrates
REMARKS: These distinctive sharks resemble rays in many respects, but unlike rays, their pectoral fins are not attached to their heads. In keeping with their benthic lifestyle, their well-developed spiracles are used for respiration, and there are barbels associated with their nostrils. Angel sharks are ambush predators that rely on crypsis to attack their unsuspecting prey (Fouts and Nelson, 1999). They are one of only a few groups of sharks that have protrusible jaws and are capable of producing strong negative pressure for suction feeding. Angel sharks are yolk-sac viviparous (Musick, 2011; Musick and Ellis, 2005). Shirai (1992b) studied their phylogenetic relationships.
REFERENCES: Compagno, 2001, 2005; Compagno, in Carpenter, 2003; Compagno and Niem, in Carpenter and Niem, 1998; Compagno et al., 2005; Fouts and Nelson, 1999; Musick, 2011; Musick and Ellis, 2005; Shirai, 1992b.
SQUATINIFORM CHARACTERISTICS:
1) body strongly depressed, ray-like
2) pectoral fins separate from head
3) eyes dorsal
4) two dorsal fins, roughly equal in size, positioned posteriorly
5) spiracles large
6) caudal peduncle with strong, lateral keels
7) anal fin absent
ILLUSTRATED SPECIMEN:
Squatina californica, SIO 65–305, 435 mm TL (dorsal view)
PRISTIOPHORIFORMES : PRISTIOPHORIDAE—Saw Sharks
DIVERSITY: 1 family, 2 genera, 7 species
REPRESENTATIVE GENERA: Pliotrema, Pristiophorus
DISTRIBUTION: Atlantic, Indian, and Pacific oceans (excluding eastern Pacific)
HABITAT: Marine; tropical to temperate; continental shelf to slope, benthic on soft substrates
REMARKS: Saw sharks, so named because of their saw-like snouts, are superficially similar to the sawfishes (Pristiformes), but differ in having the pectoral fins separate from the head, lateral gill slits, and long barbels on the ventral side of the rostrum. These sharks are yolk-sac viviparous (Musick, 2011; Musick and Ellis, 2005) and have litters of 7–17 pups. The large rostral teeth lie flat until after birth. The one species of Pliotrema, P. warreni, is unusual in having six gill slits. These sharks feed on small fishes, crustaceans, and squids, and occasionally are utilized as food fishes.
REFERENCES: Compagno, 1984a; Compagno, in Carpenter and Niem, 1998; Compagno, in Carpenter, 2003; Compagno, 2005; Compagno et al., 2005; Musick, 2011; Musick and Ellis, 2005.
PRISTIOPHORIFORM CHARACTERISTICS:
1) snout extremely long, depressed, with rows of lateral and ventral teeth
2) barbels long, ventral and anterior to nostrils
3) all five (or six) gill slits lateral and usually anterior to pectoral fin
4) spiracles large
5) lateral ridge on caudal peduncle
6) anal fin absent
7) head depressed, body cylindrical
ILLUSTRATED SPECIMEN:
Pristiophorus japonicus, SIO 92–164, 1,128 mm TL (dorsal view)
BATOIDEA—Skates and Rays
The
