their Rajiformes are not recognized here in this superorder but are placed in a separate taxon. J.G. Maisey in 1980 recognized this group by its unique form of jaw articulation, the orbitostylic jaw articulation, hence the group can be referred to as the orbitostylic sharks.
de Carvalho (1996) Superorder Notidanoidea
Order Hexanchiformes (2) Superorder Echinorhinoidea Order Echinorhiniformes Superorder Squaloidea Order Squaliformes (6) Superorder Hypnosqualea Order Squatiniformes Order Pristiophoriformes Order Rajiformes (unstated)
Shirai (1996) Order
Order Echinorhiniformes Order Dalatiiformes (4) Order Centrophoriformes Order Squaliformes Order Squatiniformes Order Pristiophoriformes Order Rajiformes (12)
Order Hexanchiformes (2)
Order Echinorhiniformes Order Squaliformes (6)
Order Squatiniformes Order Pristiophoriformes
Five orders, 11 families, 32 genera, and 124 species.
Order HEXANCHIFORMES (Notidanoidei) (8)—six-gill sharks. One dorsal fin, without spine; anal fin present; six or seven gill slits; eyes without nictitating fold; spiracle present but small, well behind eye. The homology of the extra arches is discussed by Shirai (1992b).
Two families with four genera and five species. Shirai (1992a, 1996) considered Chlamydoselachus to be sister to all remaining euselachians, and he thus placed it in a separate order from the Hexanchiformes. The evidence of de Carvalho (1996) that it and the Hexanchidae are sister taxa is accepted here. Fossil forms include the Lower Jurassic to Paleocene Orthacodontidae with one genus, Sphenodus (synonym Orthacodus) (Cappetta, 1987), Jurassic Notidanoides (the formerly recognized generic name Notidanus is invalid) (Maisey, 1986a), Late Cretaceous to Eocene Notidanodon (Cione, 1996), and perhaps, unexpectedly, Devonian teeth placed in the family Mcmurdodontidae (Turner and Young, 1987).
Family CHLAMYDOSELACHIDAE (31)—frill sharks. Marine, continental and insular slopes, occasionally on shelves; scattered in western North Atlantic, eastern Atlantic (Norway to around South Africa), southwestern Indian, western Pacific (Japan to New Zealand), and eastern Pacific (California and Chile).
Six gill openings, margin of first gill continuous across throat; mouth terminal; teeth alike on upper and lower jaws, with three elongate cusps; lateral-line canal open; body very elongate. Maximum length about 1.9 m.
One species, Chlamydoselachus anguineus, Frill Shark; possibly an unde-scribed species off southern Africa (Compagno, 1999, 2005).
Family HEXANCHIDAE (32)—cow sharks. Marine, temperate to tropical, continental and insular shelves and slopes; circumglobal, Atlantic, Indian, and Pacific.
Six or seven gill openings, margin of first gill not continuous across throat; mouth ventral; teeth in upper jaw different from those in lower jaw; lateralline canal open in Notorynchus. Maximum length about 4.7 m, attained in Hexanchus griseus.
The braincase of Notorynchus is described by Maisey (2004b), based on highresolution scanning and digital imaging. This study also gives new phyloge-netic information on the elasmobranch braincase in fossils.
Three genera and four species (Compagno, 1999, 2005): Hexanchus (2) with six gill openings, and Heptranchias perlo (sometimes placed in its own family Heptranchiidae) and Notorynchus cepedianus (sometimes placed in its own family Notorynchidae) with seven gill openings.
Order ECHINORHINIFORMES (9)—bramble sharks. Bramble sharks are placed in their own order by de Carvalho (1996) based on several characters that he feels suggest that this taxon is sister to all remaining sharks (Squaliformes, Squatiniformes, and Pristiopriformes) and to the rays (batoids). They are treated in their own order here but the noted sister-group relationship is not adopted (see under infraclass Euselachii). The only family was recognized in the Squaliformes in the last edition and in Compagno (1999).
Family ECHINORHINIDAE (33)—bramble sharks. Marine, cool to warm temperate, continental and insular shelves and slopes and some sea mounts; Atlantic, western Indian, and Pacific.
Both dorsal fins small and spineless, first dorsal fin originating over or behind pelvic fin origin (some other sharks such as the dalatiid Isistius have posteriorly placed dorsal fins, but they are not as far back); pelvic fins larger than second dorsal fin; body with coarse denticles; teeth alike in both jaws, rows linearly arranged; last gill slit distinctly larger than others; spiracles minute and well behind eyes; lateral-line canal open; caudal fin without a subterminal notch. Maximum length up to 2 m.
One genus, Echinorhinus, with two species (Compagno, 1999, 2005), E. bru-cus (shown in figure) in parts of the Atlantic (commonest in eastern Atlantic), Indian, and western Pacific with denticles relatively few and large, and E. cookei in parts of the Pacific with denticles relatively numerous and small.
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