What bill features distinguish most Anatidae from screamers?

Most members of the family Anatidae—which includes ducks, geese, and swans—are distinguished from screamers (family Anhimidae) by two primary bill features:

• Skin-covered surface: The bills of Anatidae are covered in skin, whereas screamers possess a short, nonlamellate bill that is slightly hooked and resembles that of a domestic hen.12
• Lamellate edges: Anatidae bills are characterized by lamellate edges—structures used for filtering or gripping food—while the bills of screamers lack these lamellae.12

Additionally, while Anatidae typically have a thick, fleshy tongue, screamers possess a horny tongue. These anatomical differences reflect the diverse feeding strategies of waterfowl, which have undergone significant adaptive radiation, compared to the screamer's bill, which is specifically adapted for tearing aquatic plants.2