Cascudinhos from Southern Brazil: Systematics, Endemism, and Relationships (Siluriformes, Loricariidae, Hypoptopomatinae)

Epactionotus, a new genus of the loricariid catfish subfamily Hypoptopomatinae with three new species, and a new species of Eurycheilichthys are described from southern Brazil. Epactionotus is diagnosed among genera of the Hypoptopomatinae by the posterior position of the dorsal fin and morphology of its internal supports and by absence of an expanded fleshy flap on the dorsal surface of the first pelvic-fin ray of males. The three Epactionotus species are each endemic to a very limited geographic area along the Atlantic coast of southern Brazil. Epactionotus bilineatus n. sp. is restricted to the rivers Maquine and Tres Forquilhas in northeastern Rio Grande do Sul State, E. itaimbezinho n. sp. is endemic to the rio Mampituba along the border between Rio Grande do Sul and Santa Catarina States, and E. gracilis n. sp. is endemic to the rio Ararangua drainage of southern Santa Catarina State. These new species are distinguished based on morphometric comparisons, color pattern, and arrangement of abdominal platelets. Eurycheilichthys limulus n. sp. is described from the upper reaches of the rio Jacui drainage in Rio Grande do Sul State. This new species shares with its sole congener, E. pantherinus, a single synapomorphy, presence of seven branched pectoral-fin rays, and is distinguished from it by a more narrow body, head and dorsal trunk with series of longitudinal light stripes, versus scattered dark blotches, and presence of an accessory ceratobranchial flange and filamentous gill rakers, versus absence of those features in E. pantherinus. In addition to the presence of longitudinal stripe coloration and accessory teeth, these four species also share with several other, but not all hypoptopomatines, a peculiar slitlike morphology of the skin at the base of the pectoralfin spines, the function and biological significance of which is unknown. I Laborat6rio de Ictiologia, Museu de Ciencias e Tecnologia da PUCRS, Av. Ipiranga, 6681; 90619-900 Porto Alegre, RS, Brazil. E-mail to [email protected]. 2 Associate Curator, Department of Ichthyology, American Museum of Natural History. Reprint requests to [email protected]. Copyright C American Museum of Natural History 1998 ISSN 0003-0082 / Price $3.00 AMERICAN MUSEUM NOVITATES