Pseudocetonurus septifer Sazonov & Shcherbachev 1982

Seven branchiostegal rays. Head notably large and broad; preopercle and suborbital bones deep and large, opercle commensurately small; orbit small, 19%-30% HL, diameter much less than broad interorbital; snout high, slightly projecting beyond mouth. Mental barbel small, 10% or less of HL. Gill opening wide, extending forward to below hind end of maxilla; gill membranes loosely and narrowly attached to isthmus. Gill rakers usually 16-17 on inner series of 1st arch. Teeth small, close-set, in narrow tapered band on premaxilla, uniserial on dentary. Scales with numerous small, awl-shaped spinules; no reticulations on anterior field; lateral line scales absent, a series of dark papillae in their place. Vent about halfway between pelvic fin insertion and anal fin origin (usually closer to pelvic insertion), surrounded by a black, oval to teardrop-shaped naked area and preceded by a small, round dermal window of light organ between pelvic fin bases. Pyloric caeca short, 22-24. Color black to dark brown overall (Ref. 54421).

分布於太平洋區，包括夏威夷及臺灣東北部海域。

非常罕見之魚種。

體型延長，側扁；口前長區域垂直無頃斜角度。頭部大，寬且高。鼻窩甚小。眼小；眼框間距大，且具不規則凹陷 ，框下區寬且高。吻部短而鈍， 吻尖端有一小突起。口中大，次端位，不越過眼框後緣；齒小，呈錐狀。具退化性頤鬚。前鰓蓋骨特別寬大；上鰓蓋骨後緣形成一喙狀突起。體被櫛鱗， 頭部無特化之強棘鱗，鼻吻部腹側被鱗，喉峽部裸出；頭部側線孔明顯 ，體側無側線孔，但具些許乳頭狀突起。發光器小，呈水滴狀，位於兩腹鰭間。肛門遠離臀鰭起點，靠近兩腹鰭基底間。鰾發達。幽門垂短而不分枝。

深海底棲習性，為單型種，非常稀有，全世界僅三尾標本，在本科魚類體型中屬中型，紀錄體長可達39公分左右。

Pseudocetonurus septifer is a species of rattail, the only known species in the genus Pseudocetonurus. This fish is found at depths of up to 950 m in the waters around Hawaii and in the south-eastern Pacific. It has recently also been recorded on the other side of the Pacific, near Taiwan, and this species probably has a pan-Pacific distribution but has been underrecorded due to the depths in which it lives.

This species attains a length of up to 39 cm. It is unique among rattails in having 7 branchiostegal rays and a large gill opening. This is a generally very dark, sometimes black, fish with a very large head and small, widely spaced eyes. There is a small bioluminescent organ located between the pelvic fins.

Known from seamounts and knolls