The screamers are three South American bird species placed in family Anhimidae. They were thought to be related to the Galliformes because of similar bills, but are more closely related to ducks (family Anatidae), and most closely related to the magpie goose. The clade is exceptional within the living birds in lacking uncinate processes of ribs. The three species are: The horned screamer (Anhima cornuta); the southern screamer or crested screamer (Chauna torquata); and the northern screamer or black-necked screamer (Chauna chavaria).