The two new fossil species, from a distance, would have looked like modern penguins, Fordyce said.
"Up close, however, it is clear that both species had relatively longer bills and a more slender body than in living species," he explained. "The wing was probably able to flex a little more."
Their long beaks would have enabled these penguins to spear prey, such as fish and squid. Sharks and shark-toothed dolphins, a type of prehistoric super strong dolphin with heavily toothed jaws, probably hunted the enormous penguins, which could have snapped back with their beaks.
The research team, which also included Craig Jones, mentioned that the oldest known penguin so far is Waimanu from New Zealand.
"It lived 55-60+ million years ago, not long after the extinction of dinosaurs," Fordyce said.
Ksepka said one theory holds that penguins lost their ability to fly after the Cretaceous mass extinction. DNA evidence indicates that the closest living relatives of penguins are tubenose seabirds, such as albatrosses and petrels. Since the latter can dive to significant depths, the scientists suspect that the first penguins could both fly and dive underwater.