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Early Penguins Liked It Hot
25 June 2007 (All day)
A newly found fossil indicates that giant 1.5-meter-tall penguins with enormous beaks waddled about the tropics 36 million years ago. This and another new fossil species are shaking up early penguin history, because they suggest that ancient species headed north earlier than supposed and thrived in balmy climes during one of Earth's warm spells.
Until now, penguin history has been written from scattered fossil fragments found mostly in New Zealand, Antarctica, and Australia. From those fragments, researchers deduced that penguins first appeared about 61 million years ago, venturing north to the tropics once Earth cooled in the last few million years. A single 40-million-year-old bone fragment found at the southernmost tip of South America indicates that the birds may have dispersed into new territory but still kept to chillier latitudes.
Now, fossils found in southern Peru suggest a rewrite is needed. A near-complete skeleton, the best preserved ancient penguin to date, reveals the 10th known species of extinct giant penguin, Icadyptes salasi. Its skull, the first found of these ancient birds, had a bigger, sharper beak than any previously seen. The notion of a species twice the size of an Emperor penguin in warm latitudes contradicts the trend in birds linking colder climates with larger body size.
The other new species, Perudyptes devriesi, stood nearly a meter high--about as tall as today’s King penguin. And at 42 million years, the newly found fossil smashes the record for first penguin in the tropics. The penguins seem to have found their way to Peru in separate waves from Antarctica and New Zealand, possibly driven by changes brought about by new ocean circulation patterns with the opening of Drake's Passage. The team, led by vertebrate paleontologist Julia Clarke of North Carolina State University in Raleigh, reports its findings online this week in the Proceedings of the National Academy of Sciences.
"No one predicted that penguins reached the equator before about 10 million years ago," says Clarke, "and here we show them at 42 million years at least." The two newly described species, along with unpublished data indicating the presence of three others, suggest that penguins diversified in the heat, not after chillier temperatures set in.
The Peruvian discoveries expand the early geographic range significantly, says Ewan Fordyce, a vertebrate paleontologist at the University of Otago in Dunedin, New Zealand. Despite some patchy parts to the fossil record, he agrees with Clarke's theory that today's penguins evolved some 10 to 12 million years ago, in contrast to molecular data that pegs their origins at 40 million years ago. He notes that the early diversity and range of giant penguins strengthens the argument that they evolved large bodies as an adaptation unrelated to a cooling climate.