Hesperornis, hehs puh RAWR nihs, is the name given to numerous species of diving birds that lived primarily in North America about 70 million to 90 million years ago, during the late Cretaceous Period. These birds looked somewhat like grebes or loons but had undeveloped wings and could not fly. They had teeth on their jaw and propelled themselves through water with their feet. They fed on fish. The largest species, Hesperornis regalis, measured about 5 feet (1.5 meters) long. Hesperornis fossils have been found in the western half of the United States--especially Kansas--and in western Canada and Alaska. See also Bird.