Kelenken was a large, flightless predatory bird that lived during the Miocene epoch, around 15 million years ago, in what is now Argentina. It belonged to a group known as terror birds (Phorusrhacidae) and is notable for having the largest known bird skull, measuring about 71 cm (28 inches) in length. Standing up to 3 meters (10 feet) tall, Kelenken was a fearsome predator, using its sharp beak and powerful legs to hunt small mammals and other prey. Its massive size and agility made it one of the top predators in its ecosystem. Fossils of Kelenken provide valuable insights into the diversity of ancient birds in South America.