Cladocaecum tomasscholzi n. gen., n. sp. infects the heart (lumen of ventricle) of driftwood catfish, Ageneiosus inermis Linnaeus, 1766 (Siluriformes: Auchenipteridae) from the Nanay River (Amazon River Basin, near Iquitos, Peru). It differs from all other aporocotylid genera by having a highly branched intestine comprising a central cecum that terminates immediately anterior to the ovary and that has numerous laterally directed diverticula. Kritsky platyrhynchi (Guidelli, Isaac, and Pavanelli, 2002) n. gen., n. comb. (= Plehniella p.) is redescribed based on paratypes plus new specimens collected from the body cavity of the type host (porthole shovelnose catfish, Hemisorubim platyrhynchos Valenciennes, 1840) (Pimelodidae) from the nearby Itaya River. Kritsky differs from Sanguinicola Plehn, 1905, Plehniella Szidat, 1951, Nomasanguinicola Truong and Bullard, 2013, and Cladocaecum by the combination of having a spinous anterior sucker, an intestine comprising 6 asymmetrical ceca, a lanceolate body, a straight vas deferens, an ovary with finger-like lateral projections, a small and spheroid oötype, numerous, minute, spheroid uterine eggs, and separate genital pores. An updated list of hosts, tissues infected, and geographic localities for the catfish blood flukes (9 spp.; 5 genera) is provided. This is the first report of a fish blood fluke infecting a member of Auchenipteridae and first proposal of a new genus of blood fluke (Schistosomatoidea) from South America in 64 yr. It brings the total number of Amazonian fish blood flukes to a mere 4 species.