| Family | Scientific Name | Author | Year | Common Name |
| Myctophidae | Diaphus problematicus | Parr | 1928 | Problematic Headlightfish |
All Diaphus Species: Three or more Prc (1 may be at or above lateral midline at base of caudal peduncle). Dn present; either 2 horizontal Pol near lateral line or VO1-3 on a straight ascending line with VO4-5 level. VO1-3 on a straight, inclined, ascending line with VO4-5 level; caudal glands absent; 1 Pol. More than 1 pair of luminous glands on head (Ant, Dn, Vn, or So); usually a luminous scale at PLO (FAO 2002).
Diaphus problematicus
Unique Characteristics: So absent. Dn small, shallowly embedded and directed laterally; Vn equally small, completely separated from Dn and located at ventral margin of orbit, or somewhat larger and located at anteroventral margin of orbit and connected with Dn by a narrow streak of luminous tissue between eye and nasal apparatus. Total gill rakers 15 or less; SAO3 and Pol 1-1.5 photophore diameters below lateral line (FAO 2020).
Similar Species:
Diaphus bertelseni – Biglights Lampfish
Diaphus brachycephalus – Shorthead Lanternfish
Diaphus dumerilii – Disjunctlight Lanternfish
Diaphus fragilis – Fragile Headlightfish
Diaphus garmani – Wide Lanternfish
Diaphus lucidus – Spotlight Lanternfish
Diaphus metopoclampus – Bluntnose Lanternfish
Diaphus minax – “Minax” Lanternfish
Diaphus mollis – Soft Lanternfish
Diaphus perspicillatus – Flatface Lanternfish
Diaphus rafinesquii – Lightscale Lampfish
Diaphus splendidus – Splendid Lanternfish
Diaphus subtilis – Flabby Lanternfish
Diaphus taaningi – Slopewater Lanternfish
Diaphus termophilus – Warmwater Headlightfish
References:
(FAO 2002). The living marine resources of the Western Central Atlantic. Volumes 1-3. K.E. Carpenter (ed.). Food and Agriculture Organization of the United Nations, Rome, Italy. 4099p. (Available at: http://www.fao.org/3/y4160e/y4160e00.htm).
(FAO 2020). Sutton, T.T., P.A. Hulley, R. Wienerroither, D. Zaera-Perez, and J.R. Paxton. 2020. Identification guide to the mesopelagic fishes of the central and south east Atlantic Ocean. FAO Species Identification Guide for Fishery Purposes. Rome, FAO. 2020. https://doi.org/10.4060/cb0365en.
Nafpaktitis, B.G. 1966. Two new fishes of the myctophid genus Diaphus from the Atlantic Ocean. Bulletin of the Museum of Comparative Zoology, Volume 133 (No. 9): 401-424.
Parr, A. E.1928. Deepsea fishes of the order Iniomi from the waters around the Bahama and Bermuda islands. With annotated keys to the Sudididae, Myctophidae, Scopelarchidae, Evermannellidae, Omosudidae, Cetomimidae and Rondeletidae of the world. (Scientific results of the third oceanographic expedition of the “Pawnee” 1927). Bulletin of the Bingham Oceanographic Collection Yale University Volume 3 (Article 3): 1-193.