Maximum length about 105 cm, attained in Albula vulpes.
Subfamily Albulinae. Most tropical seas (rarely brackish and freshwater).
Dorsal fin base short, 16-21 rays (last ray of dorsal fin prolonged into a filament in Albula nemoptera); branchiostegal rays 10-16; gill rakers 15-17; lateral line scales 66-84; vertebrae 69-80; small median gular plate; maxilla and basihyal toothless; crushing dentition on parasphenoid.
One genus, Albula, and at least three species (e.g., Smith, 2003; see Nelson et al., 2004:194, for a discussion from the literature concerning number of valid species of Albula that may be recognized).
Subfamily Pterothrissinae. Eastern Atlantic (Gulf of Guinea) and Japan.
Dorsal fin base long, about 55-65 rays; branchiostegal rays 6; lateral line scales 85-112; vertebrae about 107; gular plate absent; maxilla each with six or seven small teeth.
One genus, Istieus (synonym Pterothrissus), with two species: I. belloci from tropical west Africa and I. gissu from Japan. C. R. Robins (in Böhlke, 1989:9-23) noted the 1973 evidence of P. L. Forey for synonymizing the genus Istieus, based on fossil species, with the similar extant species.
Suborder Notacanthoidei (Lyopomi and Heteromi). Body eel-like; posteriorly directed spine on dorsal edge of rear of maxilla; premaxilla and maxilla bordering upper jaw; gill membranes separate; pectoral fins relatively high on body; pelvic fins abdominal, with 7-11 rays (the two fins are usually connected
by a membrane); anal fin base long and merged with what remains of the caudal fin; caudal fin skeleton reduced or absent; tail easily regenerated when lost (analogous to loss of tail in lizards?); branchiostegal rays 5-23; swim bladder present. Some have photophores.
D. G. Smith (in Bohlke, 1989:955-59) described the leptocephalus larva. The 300 or more myomeres are V-shaped. A normal caudal fin is absent but there is a postcaudal filament. The dorsal fin is short, consisting of about 10 rays, and is located in the anterior half of the body. Older larvae have small pelvic fins. The larvae, which can be exceptionally large, reach a length of up to 2 m before metamorphosis. Generic names applied to notacanthoid larvae include Tilurus and Tiluropsis.
Members of this deep-sea order have been taken between 125 and 4,900 m, but most seem to occur at depths of 450-2,500 m.
Six genera with about 25 species (e.g., Sulak, 1977; Smith, 2003).
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