After the death of the dinosaurs, and before the development of large mammals, birds were the main predators. Some of these were fearsome, and very similar to some of the dinosaurs they replaced. Diatryma stood 3 m tall, with massive legs and talons. It was flightless, with the lightweight bones of a bird. These allowed it to run and to manoeuvre itself quickly. With its huge slashing beak it would have been able to tackle prey such as the ancestors of modern horses. These birds died out when the first predatory mammals appeared. These small fast mammals probably ate the eggs and chicks of this flightless monster, which was obliged to nest on the ground and would have been very vulnerable.
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