Polyipnus is a genus of oceanic ray-finned fish in the family Sternoptychidae. This is the largest genus of the marine hatchetfishes subfamily Sternoptychinae and indeed of the entire Sternoptychidae. It is not quite as apomorphic as their relatives; it may be that the genus is actually a paraphyletic assemblage of less advanced Sternoptychinae and would need to be split.
Fossils of this genus show that they have existed at least since the Early Oligocene, about 30 million years ago.
Species There are currently 34 recognized species in this genus: Polyipnus aquavitus R. C. Baird, 1971 (aquavit hatchetfish) Polyipnus asper Harold, 1994 Polyipnus asteroides L. P. Schultz, 1938 Polyipnus bruuni Harold, 1994 Polyipnus clarus Harold, 1994 (slope hatchetfish) Polyipnus danae Harold, 1990 Polyipnus elongatus Borodulina, 1979 Polyipnus fraseri Fowler, 1934 Polyipnus indicus L. P. Schultz, 1961 Polyipnus inermis Borodulina, 1981 Polyipnus kiwiensis R. C. Baird, 1971 (kiwi hatchetfish) Polyipnus laruei Vourey, Dupoux & Harold, 2017 (bigeye hatchetfish) Polyipnus laternatus Garman, 1899 Polyipnus latirastrus Last & Harold, 1994 (comb-side hatchetfish) Polyipnus limatulus Harold & Wessel, 1998 Polyipnus matsubarai L. P. Schultz, 1961 Polyipnus meteori Kotthaus, 1967 Polyipnus notatus Harold, I. M. Kemp & Shore, 2016 Polyipnus nuttingi C. H. Gilbert, 1905 (Nutting's hatchetfish) Polyipnus oluolus R. C. Baird, 1971 Polyipnus omphus R. C. Baird, 1971 Polyipnus ovatus Harold, 1994 Polyipnus parini Borodulina, 1979 Polyipnus paxtoni Harold, 1989 (Paxton's hatchetfish) Polyipnus polli L. P. Schultz, 1961 (round hatchetfish) Polyipnus ruggeri R. C. Baird, 1971 (rugby hatchetfish) Polyipnus soelae Harold, 1994 (Soela hatchetfish) Polyipnus spinifer Borodulina, 1979 Polyipnus spinosus Günther, 1887 (spiny hatchetfish) Polyipnus stereope D. S. Jordan & Starks, 1904 Polyipnus surugaensis Aizawa, 1990 Polyipnus tridentifer McCulloch, 1914 (three-spined hatchetfish) Polyipnus triphanos L. P. Schultz, 1938 (three-light hatchetfish) Polyipnus unispinus L. P. Schultz, 1938
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