Look out over the quarry. At the top of the quarry, thousands of years ago, a stream deposited fossil mammal bones there in a three-foot deep mixture of clay and sand. The paleontologists marked the area into square-meter sections with stakes. Do you have permission to hunt and dig? Great! Now plan your fossil hunt.

• What do you need to be careful of?
• What will the bones look like?
• What are the grid lines for?
• How will you dig?
• What must you remember to do?
• How will you protect your find?

Remember

• You need to stay away from the quarry rim. It's a long drop to the bottom.
• Take a GPS reading for the site and record it in your notebook.
• The bones are reddish brown, colored by the clay around them.
• The grid markers are used to show the locations of the bones in relation to the site and to each other. Your compass is used determine the orientation of the long axis of the bone.
• The clay and sand are softer than the limestone; so digging is easier. But you can't start shoveling-you might break a fossil skull. So carefully poke around with one of your tools. When you find a bone, dig around it with a small hand-shovel and then with a small knife. If the skeleton is really large, such as a ground sloth, you would have to dig a trench around it large enough for people to stand in.
• Document everything you see and do in your field notebook, using words and photographs or sketches of your works as it proceeds.
• Prepare toilet paper and plaster jackets, especially for the skull.

Take a Breather

Great job! Step back and look at what you've uncovered. Here are some questions to ask once you've found a vertebrate fossil.

• Do you have many bones, one bone, or just a piece of bone?
• Are the bones long, short, round, flat, thick, thin? How long or thick?
• What part of the body do you think the bones came from?
• Did you find any teeth? Are they chisel-shaped like your incisors, pointed like your canine teeth, or flat like your molars? Are they worn down or sharp?

  

Getting to Know You: What do teeth and bones tell you about an animal?

With just an animal's bones and teeth you can deduce its age, size, diet, method of locomotion, and state of health. However, before we continue, we should clarify what we mean by "age." By age, in this instance we mean the age of the individual animal when it died. When we talk of geologic age, we mean the age when the animal lived. For example, an animal may have lived 20,000 years ago (geologic age) but may have been just a few years old when it died (age of the individual animal).

Here are some examples:

• Here is a skull from a bison. In mammals, the age of an individual when it died can be determined from its fossilized teeth. For example, fossil jaws that preserve deciduous (baby) teeth show that the individual died before reaching maturity. Permanent teeth become increasingly worn through life by contact with food and other teeth, so fossils with teeth that have been heavily worn indicate the individual was an older adult at its time of death. By looking at the teeth of this bison, can you tell whether or not it was young or old when it died?

ANSWER: The worn molar teeth of this bison show it was an older individual when it died.

• Here are two femurs (thigh bones) The size and shape of bones tells us how big or small an animal was when it was alive. Compare the shape of the fossil ground sloth (top) and modern human (bottom) thigh bones. How does the shape compare?

ANSWER: The thigh bone from the ground sloth is much thicker because it has to help bear the weight of a much heavier animal.

• Here are two sets of jaws. One animal eats flesh (carnivore); the other eats plants (herbivore). Which jaw is which? To get the answer, you need to look at the teeth. Sharp teeth usually indicate a meat eater. Teeth with wide chewing surfaces indicate an animal that ate grass or other types of vegetation. If the teeth on your fossil were sharp, what would it have eaten?

ANSWER: It would have been a carnivore, a meat eater.

• Here are two skulls, one from a predator and one from a prey animal. Run your mouse over the picture to locate the eye sockets. Eyes that point more forward in the skull provide better binocular vision for depth perception - something predators need to stalk prey. Eyes that are directed more toward the side give a wide range of vision - something prey animals need to watch for danger. Which skull comes from a predator and which from its prey?

  

ANSWER: The right skull comes from a predator, a sabertooth cat, and the left skull comes from its prey, a mesohippus, a primitive relative of the modern horse.