Plectrogenium

Plectrogenium was originally named as a monotypic genus in 1905 by the American ichthyologist Charles Henry Gilbert when he described what was then considered to be its only species,^[1] Plectrogenium nanum, from Hawaii.^[2] The genus name, Plectrogenium, is a compound of plectro, which means "spur", and genys, which means "cheek" or "chin", an allusion to the lines of robust spines along the sides of the head.^[3]

The currently recognized species in this genus are:^[1]

• Plectrogenium barsukovi Mandritsa, 1992
• Plectrogenium capricornis Matsunuma, Uesaka, Yamakawa & Endo, 2021
• Plectrogenium kamoharai Uesaka, Yamakawa, Matsunuma & Endo, 2021
• Plectrogenium kanayamai Uesaka, Yamakawa, Matsunuma & Endo, 2021
• Plectrogenium longipinnis Matsunuma, Uesaka, Yamakawa & Endo, 2021
• Plectrogenium megalops Matsunuma, Uesaka, Yamakawa & Endo, 2021
• Plectrogenium nanum C. H. Gilbert, 1905
• Plectrogenium occidentalise Matsunuma, Uesaka, Yamakawa & Endo, 2021
• Plectrogenium rubricauda Matsunuma, Uesaka, Yamakawa & Endo, 2021
• Plectrogenium serratum Matsunuma, Uesaka, Yamakawa & Endo, 2021

Plectrogenium is characterised by having a laterally compressed body with a number of spines and ridges on the head. There are venom glands on the spines in the dorsal, anal and pelvic fins.^[4] The dorsal fin typically has 12 spines and 7¹/₂ soft rays, the dorsal fin is split into 2 fins with 2 spines in the anterior part of the second dorsal fin. There are between 22 and 25 rays in the pectoral fins and they have 30-35 vertical rows of ctenoid scales on the body. There are flattened spines on the suborbital ridge which resembles that of the Platycephalidae. The mouth is positioned ventrally.^[5] They are small fishes with standard lengths of less than 10 cm (3.9 in)^[6]

Plectrogenium is found in the Indian and Pacific Oceans from Madagascar to Hawaii.^[7] They are bathydemersal fishes which are found at depths greater than 250 m (820 ft).^[4]