Nominal species from north and northeast South America, traditionally recognized in the literature as synonymous of Cathorops spixii (Agassiz, 1829), have their specific status redefined. Type specimens of Arius arenatus Valenciennes, 1840, Arius fissus Valenciennes, 1840, Tachisurus agassizii Eigenmann & Eigenmann, 1888 and Arius pleurops Boulenger, 1897 were examined. Cathorops arenatus and Cathorops agassizii are considered valid, Cathorops fissus is a junior synonym of Cathorops arenatus and Cathorops pleurops a junior synonym of Cathorops agassizii. The morphometric characters traditionally used in descriptions and keys in the family Ariidae are redefined and new characters are used.
Taxonomic status; nominal species of Cathorops; redescription; South America
