hoatzin

Hoatzins are large birds — at about twenty-six inches from head to tail, they are much larger than Archaeopteryx — with a yellowish chest, brown striped back, and a long narrow tail (Figure 53). Hoatzins are unusual in several ways, one of which is that hatchling hoatzins have claws on their wings. Although some other birds have vestigial wing claws, the hoatzin is the only species known to have functional wing or hand claws.