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Ask Dr. Universe fossils
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Why do marine mammals have horizontal tails, but fish have vertical tails? – Peyton, 11, Washington

Dear Peyton,

When you think about a whale, you probably picture an enormous sea creature without legs. But what if I told you the first whale had four legs and could walk on land?

I talked about whales and other marine mammals with my friend Kevin Turner. He teaches marine biology at Washington State University.

He told me marine mammals have horizontal tails because they flex their bodies up and down to move. Fish flex their bodies side to side. Scientists think it has to do with the way different animals evolved.

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Are unicorns real? – Emma, 8, Minnesota

Dear Emma,

My favorite animated GIFs are the ones with cats riding unicorns. I’m delighted to tell you about a real unicorn that lived a long time ago: the Siberian unicorn.

The Siberian unicorn was bulky and furry. It had a big hump on its back. Its horn was three feet long. That’s as big as a human preschooler!

This real-life unicorn was a kind of rhino from Eurasia. But it was bigger than modern rhinos and probably galloped like a horse.

Scientists have known about Siberian unicorns since 1808. For a long time, they thought the unicorns went extinct 200,000 years ago. Recently, that changed. Now they think the unicorns went extinct closer to 39,000 years ago.

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When was the first bee made? – Henry, 7, Illinois

Dear Henry,

It’s easy to love bees. They’re furry and buzzy. Along with other insects, birds and bats, they pollinate about one-third of the plants we eat.

I talked about how long bees have been buzzing around Earth with my friend Silas Bossert. He’s an evolutionary biologist in the Department of Entomology at Washington State University.

“The oldest bee fossil that is really without doubt a bee is between 65 and 70 million years old,” Bossert said.

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Dr. Universe: How did the first horse change into the horses of today? -Ava, 7, Kennewick, Wash.

We can learn a lot about animals of the past from fossils, the imprints or remains we find in rocks. One fossil found in the Bighorn Basin, Wyoming helped us learn about the oldest known horses. These horses are called Sifrhippus (siff-RIP-us). They had four toes on each foot and were very small. Believe it or not, these tiny horses weighed only about ten pounds. That’s just a bit heavier than your average house cat. According to the fossil records, Sifrhippus lived somewhere between 54 and 30 million years ago. When I went to visit my friend Lane Wallett, she told me all about the history of horses. As a veterinarian and a paleontologist at Washington State University, she is very curious about both horses and fossils. Read More ...