Barathronus Goode & Bean 1886

Barathronus Goode & Bean, 1886

Barathronus Goode & Bean, 1886: 164 (type species by monotypy Barathronus bicolor Goode & Bean, 1886).

Alexeterion Vaillant, 1888: 282 (type species by monotypy Alexeterion parfaiti Vaillant, 1888).

Alexeterion: Roule 1915: 59 (junior synonym of Barathronus).

Diagnosis. Joined vertical fins and loose, transparent, scaleless skin; mouth almost vertical, with fangs (easy breakable) on vomer, dentaries and occasionally on palatines; 20–35 long rakers on anterior gill arch; dorsal fin rays 62–84, anal fin rays 46–73, pectoral fin rays 21–27 and pelvic rays 1; precaudal vertebrae 31–38 and total vertebrae 67–89; adult specimens with hour-glass formed vertebral centra; ripe males with penis-length up to 15% SL. Eyes deep-set, in larger specimens invisible or seen as two dark spots, in smaller specimens they can appear as two dark spots each surrounded by a dark ring with a diameter several times larger than the central spot. Also the eyes can appear as two forward directed areas much lighter than the surrounding tissue.

Species. Thirteen species have been referred to the genus Barathronus, but of these B. solomonensis Nielsen & Møller, 2008 was transferred to the genus Paraphyonus Nielsen, 2015 and B. unicolor Nielsen, 1984 is considered a junior synonym of B. pacificus Nielsen & Eagle, 1974 (in present paper).

This leaves 11 valid species. Five Atlantic: B. bicolor Goode & Bean, 1886, B. linsi Nielsen, Mincarone & Di Dario, 2015, B. multidens Nielsen, 1984, B. parfaiti Vaillant, 1888, B. roulei n. sp. Five Indo-West Pacific: B. affinis Brauer, 1906, B. algrahami Nielsen, Pogonoski & Appleyard, 2019, B. bruuni Nielsen, 1969, B. diaphanus Brauer, 1906, B. maculatus Shcherbachev, 1976. One in Atlantic and Pacific Oceans: B. pacificus Nielsen & Eagle, 1974.

Five of the species are known only from the holotype: B. linsi (ripe female) and B. roulei (unripe male) and three juveniles: B. bruuni, B. affinis and B. parfait of which the latter two are in a poor condition. The lack of ripe males and the restricted material make it somewhat difficult to incorporate the five species in the “Key to Barathronus species”. Additional material might improve the key and reduce/increase the number of species.