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Smithsonian National Museum of Natural History Logo The Department of Paleobiology - The Life of a Vertebrate Fossil
Level 4 - Unraveling the Story - So Much to Know
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As they study the fossil and its context, vertebrate paleontologists look for answers to many questions, such as:

  • What is it, and where does it fit on the tree of life?
  • What are its closest relatives?
  • Is it something new, a kind of animal no one has ever found before?
  • How long ago did it live?
  • How big was it?
  • How did it move? Did it walk on two legs or four? Could it run?
  • Did it have claws, and if so, were they for digging or catching prey?
  • What did it eat?
  • Where did it live, and how did it get preserved as a fossil?

Pleistocene Age (1.81 - 0.01 million years ago) giant ground sloth from Panama.

Here is the giant ground sloth that looms over visitors in the Ice Age Hall. How do you think paleontologists would answer these questions about the sloth?

  • What is it, and where does it fit on the tree of life? It is a ground sloth, and it is on the mammal branch of the tree of life.
  • What are its closest relatives? Its peg-like teeth and leg and foot bones show it's related to living tree sloths, armadillos, and anteaters.
  • Is it something new, a kind of animal no one has ever found before? No. A giant ground sloth similar to this one was first reported by Richard Owen in 1840, and many have been found since. However, complete skeletons are rare.
  • How long ago did it live? It lived during the Pleistocene.
  • How big was it? It stood ~ 7 meters (20 feet) tall on its hind feet.
  • How did it move? Did it walk on two legs or four? Could it run? It could move slowly on four legs. It could also stand on its hind legs to reach high tree branches. It probably could not run very fast.
  • Did it have claws, and if so, were they for digging or catching prey? Yes, huge claws nearly 30 cm (1 foot) long, but they were for grasping tree limbs or scraping bark off tree trunks.
  • What did it eat? Leaves, bark, and twigs. We know this because we have fossil dung (coprolites) from giant ground sloths. This example is from Arizona. Sometimes, conditions are so dry that the dung can be preserved for thousands of years with little change.

Ten-thousand year old sloth dung from a dry cave in Arizona. This specimen shows what plants this animal ate. This animal was the size of a large grizzly bear.

  • Where did it live, and how did it get preserved as a fossil? Giant ground sloths lived over much of North and South America. This one is from Panama. The sloths were preserved in a bog deposit. After excavation, the bones were so soft that after they dried out, they had to be soaked in polyvinylacetate, a chemical hardener. Mounting them was a delicate task.

Pleistocene Age (1.81 - 0.01 million years ago) giant ground sloth from Panama.

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