You may think you already know all there is to know about penguins. After all, according to Hollywood, they march, they dance, and they even surf, right? OK, maybe not. But there actually is a lot more we can learn about these popular birds, as some ancient Peruvian fossils have shown us.

Most people think of penguins as being adapted to the cold of Antarctica. But in 2005, paleontologists found the fossils of two new species near the equator, in Peru. "When I heard about the finds, finds I rushed to get a team together and to go down there and work with my Peruvian colleagues," says Julia Clarke, assistant professor of marine, earth and atmospheric sciences at North Carolina State University.

Penguins evolved in places like Antarctica and New Zealand, and, until this recent discovery, scientists thought that they moved closer to the equator only about four to ten million years ago. But these fossils were found in deposits that were 42 and 36 million years old, which meant that these two species of penguin reached equatorial regions more than 30 million years earlier than previously thought ? a complete surprise to Clarke and her paleontologist colleagues.

Clarke was also amazed by the size of one of the species, Icadyptes salasi. This prehistoric penguin would have stood around 5 feet tall, or just over one and a half meters. The fossils also included the skull of the giant penguin, the first that paleontologists had ever found. "The bones of these fossils are so well preserved," Clarke says, "that when the team saw this, this skull, the first skull of a giant penguin, [?] we were just taken aback."

The skull is over a foot long (approximately 30 centimeters), with an extremely long and narrow beak, unlike that of any penguin living today. In fact, the giant penguin and the other new species, Perudyptes devriesi, are only distantly related to the penguins that exist today.

Clarke likes to use the metaphor of a tree, to describe the penguins' evolutionary relationships. She sees all of the penguins that ever lived as branches. "Perudyptes is a branch low to the ground, and Icadyptes, the giant penguin, is somewhere in the middle," the paleontologist explains. "And then, near the top of the tree, you have one little branch, and that little branch represents the penguin diversity we have today."

According to Clarke, these prehistoric penguins are among the oldest that anyone has ever found in South America. They lived at a time when the earth was actually much warmer than it is now. As she describes it, "These penguins are really in the waning days of what we call the 'greenhouse earth' of the Paleogene period." In other words, this peak in penguin species diversity actually occurred during a period of geologic history that was so warm, the earth was lacking in polar ice caps.

So if these ancient penguins thrived under much warmer conditions, does that mean that today's penguins will easily survive global warming? Not so, Clarke warns. "Just because early parts of the penguin family tree did extremely well during these warm periods in earth's history, our new results can't be taken to say that any current global climate change would not negatively impact living penguins." As she explains, "there's a lot of evidence to suggest that living penguins may be cold-adapted, unlike most of the penguins that preceded them on earth."

Clarke also stresses that the climate is now changing much more quickly, than anything prehistoric penguins would have experienced. Her findings are published in the Proceedings of the National Academy of Sciences.