Anhima cornuta (Brisson 1760; horned screamer, aka Palamedea cornuta) skull shown belongs to Chauna torquata (Oken 1816; Southern screamer; up to 90 cm in length) Screamers are extant birds in the family Anhimae. They include the genera Chauna and Anhima . The clade lacks uncinate processes on the ribs. but has large spurs on the metacarpus. The young are precocial (able to run soon after hatching). This is a rather primitive and very vocal clade.

Large spurs arise from the distal metacarpus (as a new ossification) and from the proximal metacarpus (as the return of digit ‘0’, a digit first brought to light with the Limusaurus discovery and misinterpretation). Along with the return of digit ‘0’ we also find fused vestiges of digits 4 and 5.