Giant penguins roamed what is now Peru more than 40 million years ago, much earlier than scientists thought the flightless birds had spread to warmer climates.
Best known for their presence in Antarctica, penguins currently live on many islands in the Southern Hemisphere, some even near the equator.
But scientists thought they had not reached warm areas until about ten million years ago.
Now, researchers report in this week's online edition of Proceedings of the National Academy of Sciences that they have found remains of two types of penguin in Peru that date to 40 million years ago.
One of them was a 5-foot (1.5-metre) giant with a long, sharp beak.
Palaeontologist Mario Urbina, who worked on the study, said the characteristics of the fossil are very "strange."
"The main difference between this larger penguin and the ones we see nowadays is its typical head. We have no knowledge of other animals that existed during the era of these large penguins and we are not sure if all the penguins had such a long beak," Urbina said.
The big bird is larger than any penguin known today and the third largest known to have ever lived, he added.
The beak of the large penguin, Icadyptes salasi, "looks remarkably spear-like," he said.
But the researchers do not know its exact feeding style.
The second new species, Perudyptes devriesi, was approximately the same size as a living King Penguin, 2.5 - 3 feet (0.7 - 0.9 metres) tall and represents a very early part of penguin evolutionary history, the researchers said.
The research was funded by the National Science Foundation Office of International Science and Engineering and the National Geographic Society.