PROCEEDINGS OF THE BIOLOGICAL SOCIETY OF WASHINGTON 1 13(l):269-283. 2000. A new genus and species of inseminating fish (Teleostei: Characidae: Cheirodontinae: Compsurini) from South America with uniquely derived caudal-fin dermal papillae Luiz R. Malabarba and Stanley H. Weitzman (LRM) Departamento de Zoologia -IB, Universidade Federal do Rio Grande do Sul, Av. Paulo Gama s/n, 90046-900, Porto Alegre, RS, Brasil, and Museu de Ciencias e Tecnologia, PUCRS, Av. Ipiranga 6681, 90619-900, Porto Alegre, RS, Brazil; (SHW) Division of Fishes, Department of Vertebrate Zoology, Smithsonian Institution, Washington, D.C. 20560-0159, U.S.A. Abstract. — Kolpotocheirodon theloura, a new genus and species of the chei-rodontine tribe Compsurini, is described from the uppermost tributaries of the rio Sao Francisco and rio Parana in central Brazil. Males of the new species bear a caudal-fin organ formed by fin-ray hooks and hypertrophied elongate dermal flaps along the fin rays, mostly in the ventral lobe of the caudal fin. The largest flap, attached dorsally to the nineteenth principal caudal-fin ray (ventral principal fin ray of the ventral caudal-fin lobe), is bordered with a series of tabs, and extends dorsally over most of the flaps extending from caudal-fin rays 17 and 18. There are also a series of fleshy papillae distributed along the border of the remaining ventral caudal-fin ray flaps or along the fin rays just dorsal to the flap-bearing fin rays. These tabs and papillae are un-known in both other inseminating and all externally fertilizing characids and therefore are considered derived. The new species is referred to the Compsurini of the Cheirodontinae on the basis of a cladistic diagnosis of these taxa. The relationships of K. theloura with other inseminating compsurins bearing mod-ified caudal fins are discussed. Resumo. — Kolpotocheirodon theloura, genero e especie novos da tribo Compsurini de Cheirodontinae, e descrito para os tributarios superiores do rio Sao Francisco e rio Parana no Planalto Central do Brasil. Machos da nova especie possuem um orgao formado por ganchos nos raios da nadadeira caudal e por dobras de pele ("flaps") hipertrofiadas ao longo dos raios, principalmente no lobo ventral da nadadeira caudal. O maior "flap", conectado ao longo da face dorsal do 19° raio da nadadeira caudal (raio principal inferior do lobo ventral da nadadeira caudal), e marginado por uma serie de tabiques, e se estende dorsalmente sobre as dobras de pele originadas nos 17° e 18° raios. Existe ainda uma serie de papilas carnosas distribuidas ao longo das demais dobras de pele do lobo ventral da nadadeira caudal ou ao longo dos raios imediatamente superiores aos raios com dobras de pele. Estes tabiques e papilas sao desconhecidos em outros caracideos, tanto naqueles com inseminacao como nos com fertilizacao externa, sendo considerados como caracteres derivados. A especie nova e referida aos Compsurini em Cheirodontinae com base em uma diagnose cladistica destes taxons. Sao discutidas as relacoes de K. theloura com outros compsurineos de nadadeiras caudais modificadas. The new genus and species herein de-with modified, possibly glandular tissues, scribed (see Figs. 1-3) is a cheirodontine and hooks on the caudal fin of males. It was
A New Genus And Species Of Inseminating Fish (Teleostei : Characidae : Cheirodontinae : Compsurini) From South America With Uniquely Derived Caudal fin Dermal Papillae
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