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 Piaractus mesopotamicus (Holmberg, 1887) Fig. 15 Body deep; greatest depth contained 1.5 to 2.0 and caudal peduncle depth 8.8 to 8.9 times in SL; head length 2.7 to 4.2, predorsal distance 1.6 to 1.7 and caudal peduncle length 8.8 to 9.4 in SL; snout length 2.9 to 3.3, horizontal orbital diameter 5.2 to 5.5 and least interorbital width 1.9 to 2.1 in HL. Mouth terminal; inner row of premaxilla with 2, outer row with 6-8; inner dentary row with 2, outer with 6; maxilla with 1 or 2 teeth. Lateral line complete, with 107-119 pored scales; transverse series above lateral line with 49-54 scale rows and below with 50-55 scale rows. Ventral keel with 52-54 simple spines, plus 7 pairs of spines. Dorsal fin with 15 or 16, pectoral fin with 14-17, pelvic fin with 8 or 9, anal fin with 23- 25, and caudal fin with 19 rays. Ground color greyish, darker dorsally. Dorsal and pectoral fins dark-grey; pelvic anal and caudal fins yellowish-orange ( Graça, Pavanelli, 2007 ). Maximum standard length. 533.0 mm ( Graça, Pavanelli, 2007 ). Distribution. Paraná-Paraguay system.