- a blue-faced, crested bird, Opisthocomus hoazin, of the Amazon and Orinoco forests, having as a nestling a large, temporary claw on the second and third digits of the forelimb, for climbing among the tree branches.
- a unique South American gallinaceous bird, Opisthocomus hoazin, with a brownish plumage, a very small crested head, and clawed wing digits in the young: family Opisthocomidae
