Gastornis (name meaning "Gaston's Bird"), also known as Diatryma (name meaning "Hole Through"), is a genus of large flightless bird that originated during the Middle Paleocene epoch in what is now North America, Europe, and Asia. Standing 2 meters tall, weighing over 450 kg, and the apex predator of its time and region, this was by far the largest terrestrial animal of its day.
Thought to have been extinct for 41 million years, there are still some that remain alive on Primeval Island. In fact, they are one of the island's apex predators. They are also one of the most common birds on the island, alongside Phorusrhacos, Archaeopteryx, Teratornis, Kelenken, Dodo, Harpagornis, Iberomesornis, Giant Moa, and Ichthyornis.