The evolution of the baleen in whales

phys.org | 11/30/2016 | Staff
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Baleen whales, such as the gigantic 30m-long blue whale, are the largest animals that have ever lived on this planet. They even beat the largest of the dinosaurs. But, ironically, the secret to their success lies in their taste for tiny prey.

Living whales feed by filtering vast numbers of small fish and krill directly from seawater. This is a rather clever strategy that allows them to cut out predatory middle men and feast directly on the abundance at the bottom of the food chain.

Whales - Prey - Hallmark - Adaptation - Baleen

Modern whales are toothless and so capture their prey using their hallmark adaptation: baleen, a series of horny filtering combs that line the upper jaw. Baleen is the key feature that allowed whales to grow big.

From the time baleen first appeared, most whales grew to body lengths of four to eight metres and, ultimately, became the ocean giants we know today.

Mysteries - Marine - Evolution - Charles - Darwin

How and why baleen evolved is one of the greatest mysteries of marine mammal evolution, with even Charles Darwin himself speculating upon its beginnings in his On the Origin of Species.

Like all mammals, whales originally had teeth, which they used to capture and cut up large prey. Previously, it had been thought that baleen evolved alongside teeth in a transitional group of fossil whales known as aetiocetids.

Idea - Problem - Teeth - Baleen - Space

But this idea presents a major problem. How could hard, slicing teeth and comparatively soft baleen occupy the same space in the jaw, and yet not get in each other's way? Why did the teeth not damage the baleen every time an early whale closed its mouth?

A 25 million year old fossil whale seems to provide the answer, according to research published in the Memoirs of Museum Victoria this week by a team of palaeontologists at Museums Victoria and Monash University (including Erich Fitzgerald, Alistair Evans, Tim Ziegler and ourselves).

The new...
(Excerpt) Read more at: phys.org
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