Peixes da planície de inundação do alto rio Paraná e áreas adjacentes: revised, annotated and updated Author Ota, Renata Rúbia Author Deprá, Gabriel de Carvalho Author Graça, Weferson Júnio da Author Pavanelli, Carla Simone text Neotropical Ichthyology 2018 2018-06-11 16 2 1 111 journal article 10.1590/1982-0224-20170094 f68fe85c-2a4c-4625-b684-74f61398d6c2 1982-0224 3678395 Megalancistrus parananus (Peters, 1881) Fig. 25 Body deep; greatest body depth contained 4.0 to 4.7 and caudal peduncle depth 6.0 to 6.5 times in SL; head length 2.8 to 3.2, predorsal distance 2.2 to 2.4, dorsal-fin spine length 4.1 to 4.4, pectoral-fin spine length 3.8 to 4.3 and caudal peduncle length 3.5 to 3.8 in SL; snout length 1.2 to 1.4, horizontal orbital diameter 5.0 to 6.2 and least interorbital width 1.6 to 2.0 in HL. Mouth inferior; premaxilla with 6-8 and dentary with 8-10 teeth. Mid-lateral series with 25, predorsal series with 3, and dorsal-fin base series with 12 plates. Dorsal fin with I,10-15, pectoral fin with I,6, pelvic fin with i,5 and anal fin with 6 rays. Ground color lightbeige; several dark-brown blotches on body, as well as fins. Maximum standard length . 504.0 mm ( Graça, Pavanelli, 2007 ). Distribution. Río de la Plata basin.