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Wed May 24, 2017, 01:35 PM

Whales only recently evolved into giants when changing ice, oceans concentrated prey

Source: Phys.org

Whales only recently evolved into giants when changing ice, oceans concentrated prey

May 23, 2017

The blue whale, which uses baleen to filter its prey from ocean water and can reach lengths of over 100 feet, is the largest vertebrate animal that has ever lived. On the list of the planet's most massive living creatures, the blue whale shares the top ranks with most other species of baleen whales alive today. According to new research from scientists at the Smithsonian's National Museum of Natural History, however, it was only recently in whale's evolutionary past that they became so enormous.

In a study reported May 24 in Proceedings of the Royal Society B, Nicholas Pyenson, the museum's curator of fossil marine mammals, and collaborators Graham Slater at the University of Chicago and Jeremy Goldbogen at Stanford University, traced the evolution of whale size through more than 30 million years of history and found that very large whales appeared along several branches of the family tree about 2 to 3 million years ago. Increasing ice sheets in the Northern Hemisphere during this period likely altered the way whales' food was distributed in the oceans and enhanced the benefits of a large body size, the scientists say.

How and why whales got so big has remained a mystery until now, in part because of the challenges of interpreting an incomplete fossil record. "We haven't had the right data," Pyenson said. "How do you measure the total length of a whale that's represented by a chunk of fossil?" Recently, however, Pyenson established that the width of a whale's skull is a good indicator of its overall body size. With that advance, the time was right to address the long-standing question.

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Read more: https://phys.org/news/2017-05-whales-evolved-giants-ice-oceans.html

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Related: Independent evolution of baleen whale gigantism linked to Plio-Pleistocene ocean dynamics (Proceedings of the Royal Society B)


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