73 The Beagle, Records of the Museums and Art Galleries of the Northern Territory, 2005 21: 73–163 Review of the Dinematichthyini (Teleostei: Bythitidae) of the Indo-West Pacific. Part I. Diancistrus and two new genera with 26 new species WERNER SCHWARZHANS 1 , PETER RASK MØLLER 2 AND JØRGEN G. NIELSEN 2 1 Ahrensburger Weg 103 D, 22359 Hamburg, GERMANY wwschwarz@aol.com ² Zoological Museum, University of Copenhagen, Universitetsparken 15, DK-2100 Copenhagen Ø, DENMARK pdrmoller@snm.ku.dk, JGNielsen@snm.ku.dk ABSTRACT An ongoing revision of the dinematichthyine fishes (Ophidiiformes, Bythitidae, Brosmophycinae) of the Indo-West Pacific based on ca. 5000 specimens will be published in parts. Part I includes 765 identified specimens in the genera Brotulinella (new genus with one new species), Diancistrus Ogilby, 1899 (with four described and 23 new species) and Paradiancistrus (new genus with two new species). The main distinguishing character in this group of presumably related genera is the male pseudoclasper pattern. Brotulinella is further characterized by the slender form and the generally higher number of precaudal vertebrae (12 versus 11 in the two other genera, except for one species with 12 in Diancistrus). Paradiancistrus is unique amongst Indo-West Pacific dinematichthyine genera in having only one instead of three lower preopercular pores. Brotulina Fowler, 1946, Calcarbrotula Fowler, 1946 and Parabrosmolus Machida, 1996, are regarded as junior synonyms of Diancistrus. The separating characters of the species are male pseudoclaspers, head squamation, head pores, otoliths, morphometric proportions, and fin ray and vertebral counts. Diancistrus, which has remained monotypic for more than 100 years, is here shown to be one of the most diverse genera of tropical reef fishes. The many unrecognised species have previously been confused with other genera such as Dinematichthys and Ogilbia. Pseudoclasper morphology is used to define three informal species groups in the genus Diancistrus. KEYWORDS: viviparous brotulas, Indo-West Pacific, Australia, Indonesia, Micronesia, New Guinea, Philippines, Polynesia, Ryukyu Islands, coral reef fishes, Diancistrus, new genera, new species. CONTENTS INTRODUCTION .F 74 MATERIAL AND METHODS ............................................................................................................ 75 DEFINITION OF CHARACTERS ....................................................................................................... 75 COMPARATIVE MATERIAL ............................................................................................................ 78 SYSTEMATICS ....F 78 Tribe Dinematichthyini Cohen and Nielsen, 1978 ........................................................................... 78 Key to the genera of Dinematichthyini in the Indo-West Pacific .................................................... 78 Brotulinella n. gen. ........................................................................................................................... 79 Brotulinella taiwanensis n. sp. ................................................................................................... 80 Diancistrus Ogilby, 1899 ................................................................................................................. 82 Key to the species of Diancistrus ............................................................................................... 88 Diancistrus alatus n. sp. ............................................................................................................ 89 Diancistrus alleni n. sp. ............................................................................................................. 91 Diancistrus altidorsalis n. sp. .................................................................................................... 95 Diancistrus atollorum n. sp. ....................................................................................................... 97 Diancistrus beateae n. sp. ....................................................................................................... 100 Diancistrus brevirostris n. sp. .................................................................................................. 103 Diancistrus eremitus n. sp. ...................................................................................................... 105 Diancistrus erythraeus (Fowler, 1946)..................................................................................... 108 Diancistrus fijiensis n. sp. ......................................................................................................... 110 Diancistrus fuscus (Fowler, 1946) .............................................................................................113