LAMNID CHARACTERISTICS:

      1) second dorsal fin much smaller than first dorsal fin

      2) caudal fin nearly symmetrical (approaching lunate)

      3) caudal peduncle strongly depressed with a lateral keel and precaudal pit

      4) mouth large, extending past level of eyes

      5) gill openings large

      6) teeth large

      7) gill rakers absent

      ILLUSTRATED SPECIMEN:

      A) Isurus oxyrinchus, SIO 55–85, 875 mm TL (dorsal view)

      B) head of Isurus oxyrinchus, SIO 55–85 (lateral view)

      LAMNIFORM DIVERSITY:

      A) PSEUDOCARCHARIIDAE—crocodile sharks: Pseudocarcharias kamoharai, SIO 97–221, 952 mm TL

      B) MEGACHASMIDAE—megamouth sharks: Megachasma pelagios, SIO 07–53, 2,150 mm TL

      C) MITSUKURINIDAE—goblin sharks: Mitsukurina owstoni, SIO 07–46, 1,150 mm TL

      CARCHARHINIFORMES—Ground Sharks

      The ground sharks comprise the most speciose order of sharks, with eight families, approximately 50 genera, and at least 287 species. More than half of the species are small-bodied cat sharks (Scyliorhinidae and Proscylliidae), named for their horizontally elongate eyes. The false cat sharks (Pseudotriakidae) are characterized by a deep groove anterior to their elongate eyes, while the monotypic Barbled Houndshark (Leptochariidae) has notably long labial furrows and nostrils with barbels. The weasel sharks (Hemigaleidae) are characterized by their wavy, upper caudal-fin lobe. The Carcharhiniformes as a group are difficult to characterize, but all included species have two dorsal fins without spines, an anal fin, five gill slits (last one to three positioned over the pectoral fin), and a large mouth extending behind the eyes (Compagno, 1988). In contrast with the similar Lamniformes, the eyes of most carcharhiniforms are protected by a nictitating membrane and most species lack spiracles. Three families (Carcharhinidae, Sphyrnidae, and Triakidae) are described in more detail below.

      REFERENCES: Compagno, 1988, 2001.

      CARCHARHINIFORMES : TRIAKIDAE—Hound Sharks

      DIVERSITY: 9 genera, 47 species

      REPRESENTATIVE GENERA: Galeorhinus, Mustelus, Triakis

      DISTRIBUTION: Atlantic, Indian, and Pacific oceans

      HABITAT: Marine, occasionally in river mouths; tropical to temperate; coastal to continental slope, demersal over rocky reefs and soft substrates

      REMARKS: Hound sharks are moderately sized (to 2.4 m) and feed on benthic and midwater invertebrates and fishes. Some species specialize on crustaceans and others on cephalopods. Hound sharks are either yolk-sac viviparous or placental viviparous (Musick, 2011; Musick and Ellis, 2005) and produce litters with as many as 52 pups. Their phylogenetic relationships were studied by Lopez et al. (2006).

      REFERENCES: Compagno, 1988, 2001, 2005; Compagno, in Carpenter, 2003; Compagno and Niem, in Carpenter and Niem, 1998; Compagno et al., in Fischer et al., 1995; Compagno et al., 2005; Lopez et al., 2006; Musick, 2011; Musick and Ellis, 2005.