The similarity with the Red-billed Curassow seems to be mostly due to the fact that these are the most ancient species of the southern lineage, retaining more plesiomorphies.

Although a close relationship to the Red-billed Curassow (C. blumenbachii) has been proposed, the Wattled Curassow seems to be a quite basal lineage without particularly close relatives.

With increasing aridification of southeastern Brazil, the ancestors of the Red-billed Curassow found refuge in the mountain ranges between the Brazilian Highlands and the Atlantic during the mid-Zanclean, some 4.5-4 mya.

The Red-knobbed Curassow or Red-billed Curassow, Crax blumenbachii, is an endangered species of Cracid that is endemic to lowland Atlantic Forest in the states of Espírito Santo, Bahia and Minas Gerais in southeastern Brazil.