[MUSIC] JOAN CARTAN-HANSEN, HOST: Mammoths and mastodons look somewhat alike.

But they're very different animals.

Mastodons first appeared about 27 to 30 million years ago.

Mammoths first appeared about five million years ago and are in the elephant family.

Mastodons were shorter and stockier than mammoths.

Both had long upper tusks, but mammoth tusks have a curve while mastodon tusks grew straighter.

But the easiest way to tell them apart was by Looking in their mouths.

Mastodons ate twigs and harder vegetation.

So, they're teeth were more pointed and adapted for crushing.

Mammoths ate grasses, so their teeth were flatter and adapted for grazing and grinding.

President Thomas Jefferson was fascinated by mammoths and mastodons.

Mastodon bones found in the late 1700s were some of the first bones recognized as an unknown animal.

That's because no living animal had teeth like the fossils did.

In Jefferson's time, people didn't yet understand that some animals had gone extinct in Earth's history.

For more information about mammoths, check out the science trek website.

You'll find it at science trek dot org.