Air Date: Week of June 23, 2000

Living On Earth host Steve Curwood talks with paleontologist David Webb about the newly discovered remains of species of giant sloth that lived in Florida more than two million years ago.

Transcript

CURWOOD: It's Living on Earth. I'm Steve Curwood. Today's average three-toed sloth is about two feet long and weighs about eight pounds. Now, imagine a sloth weighing in at five tons and covered with hair. If you had been around two million years ago you might have seen such a creature. Scientists recently published findings of a new species of prehistoric ground sloth that arrived in North America much earlier than anyone had previously thought. David Webb, a paleontologist with the University of Florida, describes what a spectacle they would have created, if we could go back in time to see it for ourselves.

WEBB: They would have been a preposterous sight because not only were they surely slow-moving and gigantic, but because they have huge claws, especially on their front feet, they walked with the palms turned inward in a sort of straddling mode. The other main mode that we visualize for these beasts were reared up on their heavy tails in a tripod stance, reaching up and stripping branches, probably about 20 feet up in the air.

CURWOOD: This discovery was made, what? Back in 1986?

WEBB: We started in '86. A chance discovery by a geologist who wasn't looking at the right outcrop. And from there, we began to realize that there was a lot of this sloth, and by getting fairly complete material we began to realize that it didn't fit anything known. It had extra claws, extra fingers, different proportions. So at that point the scientific team began to work on a description, as the rest of us actually continued excavating.

CURWOOD: What does this tell us about the ecosystem back then? This fossil is, what? Two million years old? Two point two million?

WEBB: Yeah, it's just over two million. This is a time when the Panama land bridge first allowed a raft of different animals to come north out of South America. And we're a little bit struck by the fact that these gigantic sloths, which are surely eating lots of lush vegetable material, leaves, were able to come so far north so fast. In the late Pliocene, they come all the way around the coastal plain, all around the Gulf of Mexico. And that's surprisingly early, and suggests a surprisingly moderate climate, just when in other regards, in other places, the ice ages are just beginning.

CURWOOD: This all happened a long time ago. What makes it very interesting right now?

WEBB: Well, it's always interesting to look back, and I think we're always doubly fascinated with the really big animals that are totally out of character compared to anything we know today. I'm still a little bit amazed by trying to take a living tree sloth and blow it up to the scale of bigger than an elephant, and then imagine how a herd of these animals lumbered around. It tells us more about the climate. It tells us more about the pathways between South and North America. But most of all it's just the sheer fascination of wonderful beasts.

CURWOOD: David Webb is a paleontologist with the University of Florida in Gainesville. Thanks so much for speaking with us today.

WEBB: My pleasure, Steve.