Trachonurus Günther, 1887

Nakayama, Naohide, 2020, Grenadiers (Teleostei: Gadiformes: Macrouridae) of Japan and adjacent waters, a taxonomic monograph, Megataxa 3 (1), pp. 1-383 : 281

Genus Trachonurus Günther, 1887

[Japanese name: Watahige-zoku]

Trachonurus G̹nther, 1887:124 (subgenus of Macrurus ; type species: Coryphaenoides villosus G̹nther, 1887, by original designation).

Diagnosis. Anus surrounded by broad, extensive periproct that extending most of distance between anal-fin origin and pelvic-fin bases; periproct abutting anal-fin origin. Infraorbital ridge not connected with preopercular ridge, separated by distinct gap. Pelvic fin with 6–7 soft rays, its origin distinctly posterior to vertical through pectoral-fin base (usually below midbase of first dorsal fin). Second spinous ray of first dorsal fin slender, lacking serrations along its leading edge.Chin barbel present.Teeth in narrow band in upper jaw, with outer series usually enlarged; lower jaw teeth in 2–3 rows or narrow band. Scales not deciduous, closely adhered to body surfaces. Body scales adherent, covered with long, erect, needle-like spinules in quincunx pattern; buttresses well developed; reticulate pattern developed over entire scale surface. Scales along anterior parts of second dorsal and anal fins enlarged. Grooved lateral line present or absent. Head almost fully scaled; gular and branchiostegal membranes heavily scaled in most species; no scutes on head ridges and tip and lateral angles of snout. Cephalic sensory canals lacking open pores. Pyloric caeca short and thick, usually less than 15. Branchiostegal rays 7. Body uniformly dark, lacking prominent silvery reflection. [Modified from Sazonov & Iwamoto (1992) and Iwamoto & Graham (2001).]

Remarks. Although Trachonurus is a distinctive genus of the family, there is much discussion on its species-level classification. It is still uncertain how many species are included in this group, and there appears to be some species still remaining to be described ( Sazonov & Iwamoto 1992; Iwamoto 1997; Iwamoto & McMillan 1997; Iwamoto & Merrett 1997; Iwamoto & Williams 1999). The following six species are currently regarded as valid, one of which is known from Japanese waters: T. gagates Iwamoto & McMillan, 1997 distributed in Australia and New Zealand; T. robinsi Iwamoto, 1997 probably endemic to the Philippines; T. sentipellis Gilbert & Cramer, 1897 recorded from the Hawaiian Islands, Australia, the New Caledonian region, and Taiwan; T. sulcatus ( Goode & Bean, 1885) , a senior synonym of T. asperrimus ( Vaillant, 1888) , widely distributed in the Atlantic; T. villosus (G̹nther, 1877) (type species) probably confined to the northwestern Pacific from Japan to the Philippines (see the Remarks of this species); and T. yiwardaus Iwamoto & Williams, 1999 so far known from the west and south coasts of Australia.