q 2001 by the American Society of Ichthyologists and Herpetologists Copeia, 2001(4), pp. 1058–1063 New Species of Moenkhausia (Characiformes: Characidae) from the Rio Negro of Brazil FLA ´ VIO C. T. LIMA AND MO ˆ NICA TOLEDO-PIZA A new Moenkhausia species is described from the middle rio Negro of Brazil. This species shares with Moenkhausia oligolepis, Moenkhausia sanctaefilomenae, and Moenk- hausia pyrophthalma a reticulate body coloration and a red pigmentation on the dorsal margin of the eye. It can be distinguished from those species by the presence of a distinctive stripe on the caudal peduncle, a uniform anterior humeral blotch, and meristic and morphometric data. Priocharax ariel, Serrabrycon magoi, Microster- narchus fimbripinnus, and Acestridium martini are recorded for the first time from the middle rio Negro in Brazil. Uma espe´cie nova de Moenkhausia e´ descrita do me´dio rio Negro no Brasil. Esta espe´cie compartilha com Moenkhausia oligolepis, Moenkhausia sanctaefilomenae e Moenkhausia pyrophthalma um padra˜o de colorido reticulado e a pigmentac¸a˜o ver- melha na margem dorsal do olho. Distingui-se destas espe´cies pela presenc¸ a de uma faixa perspı ´cua no pedu´ nculo caudal, uma mancha umeral anterior uniforme e por dados merı ´sticos e morfome´tricos. Priocharax ariel, Serrabrycon magoi, Microsternar- chus fimbripinnus e Acestridium martini sa˜o registrados pela primeira vez no me´dio rio Negro no Brasil. A S presently defined the characid genus Moenkhausia Eigenmann consists of ap- proximately 50 species. The monophyly of Moenkhausia as well as the species level taxono- my are yet to be critically examined. Species cur- rently assigned to Moenkhausia are widespread throughout rivers of cis-andean South America. We herein describe a new, distinctive characid that we include in the genus Moenkhausia. The new species was collected in the middle rio Ne- gro in 1972 by the Expedic¸a˜o Permanente da Amazoˆnia (EPA), a project conducted by MZUSP that made extensive collecting expedi- tions in the Amazon region from 1967–1975. The 1972 EPA expedition focused on an inten- sive sampling of the small igarape´s tributaries to the rio Negro and the surroundings of Santa Isabel do Rio Negro (formerly Tapurucuara). That effort yielded excellent collections of small fishes, part of which were reported on by pre- vious authors (Weitzman and Balph, 1979; Weitzman and Fink, 1983; de Pinna, 1989). Two additional specimens were collected by Tuyuka Indians in the rio Tiquie´, a tributary of the rio Uaupe´s, during an expedition in which the first author took part. In addition to the description of the new species, we also report on new re- cords for two characiforms, one gymnotiform, and one siluriform for the middle rio Negro. MATERIALS AND METHODS Counts and measurements were taken ac- cording to Fink and Weitzman (1974:1–2). In the description, the frequency of each count is provided in parentheses after the respective count, with the count of the holotype indicated by an asterisk. The total number of specimens counted was 14, except when indicated. Verte- bral counts, pterygiophore insertions relative to neural and hemal spines, and posterior dentary teeth were recorded from a single cleared-and- stained (C&S) specimen (MZUSP 62615, 44.2 mm SL). Vertebrae incorporated into the We- berian apparatus were counted as four elements and the fused PU11U1 was considered a single element. Institutional abbreviations follow Leviton et al. (1985). Institutional catalog numbers are fol- lowed by the number of specimens in a lot, range of standard lengths, and locality infor- mation. Moenkhausia diktyota n. sp. Figure 1 Holotype.—MZUSP 62614 (52.4 mm SL), Brazil, Amazonas, rio Negro, igarape´ at Sa˜o Joa˜o, near Santa Isabel do Rio Negro, 08249S; 658029W; EPA, 23 October 1972. Paratypes.—MZUSP 62615 (9, 1 C&S, 28.4–52.3 mm SL); INPA 16200 (1, 51.2 mm SL); USNM 363175 (1, 51.5 mm SL); same data as holotype. MZUSP 64107 (2, 35.5–45.1 mm SL), Brazil, Amazonas, igarape´ Yoariwasotoamaku´ ya, tribu- tary of rio Tiquie´, comunidade de Cachoeira