Dorsal fin rays usually equal to or longer than opposing anal fin rays; anus and anal fin origin usually behind tip of pectoral fin; scales present; some with one or more spines on opercle; supramaxillary present; larvae without a vexillum; pelvics rarely absent. Maximum lengths about 1.6 m, attained by Genypterus capensis, and 2.0 m, attained in Lamprogrammus shcherbachevi.
Four subfamilies with 48 genera and about 222 species (Nielsen et al., 1999; Lea and Robins, 2003). Fossils include the Tertiary Ampheristus and Hoplobrotula.
Subfamily Brotulinae. Barbels present on chin and snout.
One circumtropical genus, Brotula (brotulas), with at least five species.
Subfamily Brotulotaeniinae. No barbels on chin or snout; scales in the form of small prickles.
One circumtropical genus, Brotulotaenia, with four species. Lamprogrammus may be better placed in this subfamily rather than in the non-monophyletic Neobythitinae (Fahay and Nielsen, 2003).
Subfamily Ophidiinae. No barbels on snout or chin; pelvic fins far forward; cycloid scales present (in regular rows or at oblique angles to each other); slender, elongate filament of bone extending anteriorly from junction of ventral arms of cleithra. Considered monophyletic by Nielsen et al. (1999).
Eight genera, one tribe, Lepophidiini (21 species), with Cherublemma, Genypterus, and Lepophidium, and the other, Ophidiini (33 species), with Chilara, Ophidion, Otophidium, Parophidion, and Raneya, with about 54 species.
Subfamily Neobythitinae. No barbels on snout or chin; cycloid scales present; no filament of bone extending anteriorly from junction of ventral arms of cleithra; pelvic fins absent in at least adults of the five species of the virtually circumtropical Lamprogrammus; eye lens minute or absent in Leucicorus and eye minute in Typhlonus. Members of this group range from the littoral to the greatest depths at which fish have been obtained (the deep-sea record being for Abyssobrotula galatheae obtained at 8,370 m in the Puerto Rico Trench). This subfamily is not monophyletic.
About 38 genera (e.g., Abyssobrotula, Acanthonus, Bassogigas, Bassozetus, Dicrolene, Eretmichthys, Glyptophidium, Homostolus, Lamprogrammus, Monomitopus, Neobythites, Petrotyx, Porogadus, Sirembo, and Spectrunculus) with about 159 species.
Suborder Bythitoidei. Anterior nostril immediately above upper lip in most species; viviparous, males with an external intromittent organ; caudal fin connected with dorsal and anal fins or separate.
Family BYTHITIDAE (223)—viviparous brotulas. Marine (rarely in brackish and fresh-waters); Atlantic, Indian, and Pacific.
Scales usually present; swim bladder present; opercular spine usually present and strong; pyloric caeca present; precaudal vertebrae 9-22. One species of Bythites is known from a thermal vent in the Galapagos Rift Zone. In contrast to ophidiids, several species of bythitids extend into shallow water. About five species are confined to freshwater or weak brackish water.
About 37 genera with 107 species (Nielsen et al., 1999; M0ller et al., 2004a,b).
Subfamily Bythitinae. Caudal fin united with dorsal and anal fins; pelvic fins absent in Bellottia and Hephthocara. The six blind to partially blind species of Lucifuga (placed in Brosmophycinae in Nielsen et al., 1999) live in limestone caves and sinkholes in waters ranging in salin-ity from fresh to highly saline; four species occur in Cuba, one in the Bahamas, and one in the Pacific in the Galapagos (Nielsen et al., 1999; Proudlove, 2005).
About 16 genera (e.g., Bellottia, Bythites, Calamopteryx, Cataetyx, Diplacanthopoma, Gerhardia, Grammonus, Lucifuga, Saccogaster, Stygnobrotula, and Tuamotuichthys) with about 62 species (e.g., M0ller et al., 2004a).
Subfamily Brosmophycinae. Caudal fin separate from dorsal and anal fins. One species of Ogilbia lives in brackishwater caves and crevices in the Galapagos, and one species of Typhliasina (T. pearsei, placed in Ogilbia in Nielsen et al., 1999, and Nelson et al., 2004) lives in freshwater caves in the Yucatan. Two tribes were recognized by Nielsen et al. (1999), Brosmophycinini and Dinematichthyini (with most of the genera).
About 21 genera (e.g., Bidenichthys, Brosmophycis, Dermatopsis, Dinematichthys, Gunterichthys, Melodichthys, Ogilbia,, Ogilbichthys, and Typhliasina) with at least 45 species (e.g., M0ller et al., 2004b).
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