Zahuranec, Bernard J. Zoogeography and Systematics of the Lanternfishes of the Genus Nannobrachium (Myctophidae: Lampanyctini). Smithsonian Contributions to Zoology, number 607,69 pages, 25 figures, 34 tables, 2000. Of those lanternfishes in the genus Lampanyctus (sensu lato) with short or no pectoral fins, 17 species are recognized, removed to the separate genus Nannobrachium, and placed into five species groups. These groups are designated Nigrum (four species), Regale (five species), Cuprarium (two species), Achirus (five species), and Isaacsi (one species). The genus Nannobrachium includes those species of the tribe Lampanyctini that are characterized by the following features: either a lack of pectoral fins or short fins with a narrow base in adults; vertically elongate, squarish otoliths with smooth margins; reduced musculature resulting in a soft, flaccid body; body profile appearing "pinched" with concave dorsal and ventral profiles behind the head; and swimbladder atrophied in adults. The four species in the Nigrum group are N. nigrum, from the tropical and subtropical Pacific and eastern Indian oceans; N. atrum, from the temperate North and South Atlantic, South Indian, and Southwest Pacific oceans; N. gibbsi, herein described from the tropical Pacific; and N. indicum, herein described from the tropical Indian Ocean. All have extremely reduced pectoral fins with downward pointing fin rays in the adult. All five species in the Regale group are confined to the Pacific Ocean: N. regale in the Subarctic and North Temperate; N. ritteri in the eastern North Pacific Subarctic and Temperate; N. fernae in the eastern North Pacific Temperate; N. idostigma in the eastern tropical Pacific; and N. bristori herein described from the North Subtropical Pacific. In the Regale group, the pectoral fin is not as reduced compared with other Nannobrachium groups, and the VLO photophore is low on the side of the body. The two species in the Cuprarium group are N. cuprarium, bipolar in the subtropical Atlantic, and N. lineatum, from the tropical-subtropical Atlantic, Indian, and Pacific oceans. Both species have black pigmentation on the posterior of the supracaudal and infracaudal luminous glands. Four of the five species in the Achirus group are herein described: N. hawaiiensis, N. crypt icum, and N. phyllisae from the North Central, Equatorial, and Southeast Pacific, respectively; and N. wisneri, circumglobal from the southern temperate and subtropical regions. The previously described N. achirus is circumglobal in the Subantarctic. In all five species, the pectoral fin becomes greatly reduced or is completely lost and covered over by skin in adults. The Isaacsi group contains only N. isaacsi from the eastern tropical Atlantic. It has the VO2 photophore raised in position, above and slightly forward of the VOj. Most of the species and species groups show remarkably little overlap in their distributions. Analysis of the distribution patterns revealed distinct patterns concordant, or largely so, with patterns recognized for o...
