Some of the largest birds in history, called pelagornithids, arose a few million years after the mass extinction that killed off the dinosaurs and patrolled the oceans with giant wingspans for some 60 million years. A team of paleontologists has found two fossils -- each from individual pelagornithids with wingspans of 20 feet or more -- that show this gigantism arose at least 50 million years ago and lasted at least 10 million years. Read more