The peculiar swamp-dwelling hoatzin (Opisthocomus hoazin) looks like a survivor from prehistory and does indeed have a strong link with the fossil Archaeopteryx. Like the ancient bird-like creature, young hoatzins have strong wing claws which they use to haul themselves about in the trees before they can fly. But the hoatzin is odd in other ways: it digests fibre, produces cow-like dung and defies classification. It eats the leaves of the moka-moka, stuffing its massive crop and then perching wi