Skull Island is home to several species of large flightless birds. The largest are heavily built, predatory species (such as phorusrhacids that live here, in a land outside the New World) with great axe-like beaks. Zeropteryx are among the heaviest of these, standing as high to its hips as a human man and with powerful running legs and huge claws. Armed with enormous razor-tipped, spade-like beaks, they are formidable predators. Anything that moves is potential game, even Ligocristus. The bladelike edge of the bird’s beak is as lethal as a pickax to smaller animals not fast enough to get away.