Hisonotus hungy sp. n. is described from the arroyo Tirica, río Paraná basin in Misiones province, Argentina. Hisonotus hungy sp. n. is diagnosed by the following combination of characters: 20-22 lateral plates, 5 branched anal-fin rays, absence of pad on snout tip, blunt and deep snout, snout 45.5-50.9 (% in HL), eye 13.4-17.1 (% in HL), predorsal unpaired plates absent; vent completely covered by two rows of large lateral platelets and one median series with irregular plates.