High in the luxuriant branches of the tropical forest trees in the northeast of the Australian continent, a black and white creature throws itself from one branch to another and disappears among the foliage. At first glance it looks like an arbrosaur, one of the tree-living coelurosaurs that are found almost all over the world. Then it appears again, and its bright face, surmounted by a high crest, is its most obvious feature. This is a crackbeak - a tree-living variety of the successful basal ornithopods.