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October 2001

Set In Stone: Finding Fossils On The Trail

You could be walking on an ancient seabed or a swamp where dinosaurs played. Look closely and you'll see history in the rocks.

On the trail, look for exposed bedrock, like rock outcrops or bluffs. “Rock layers sometimes fall from these overhanging roofs, creating fresh surfaces to search for fossils,” says McFarland. “Another good place to look is where streams run directly over bedrock, such as at cutbanks. The stream polishes the rock to show more detail than you can see in rock that’s just exposed to weather.”

Since 90 percent of known fossils are marine animals, forget about looking for a T. rex skeleton and look instead for sea-dwellers like the trilobite, which is to invertebrate fossil hunting what the grizzly is to wildlife watching-what everyone wants to see. These buglike critters (arthropods, actually, that vanished 225 million years ago) resemble a matchbox-size horseshoe crab and are one of the few fossil types in which the body tends to stay articulated.

If a trilobite is the invertebrate grizzly, then the crinoid, or sea lily, is the oh-so-common rabbit. The “buttons” you see imprinted in rocks are the crinoids’ bases, which they used to anchor themselves to the seafloor. The crinoid’s arms, which resembled flowers, were rarely preserved.

Another common find is the brachiopod, whose fossilized remains resemble a mold of a thickly ridged mussel in rock. These 1 1/2-inch bivalve (two-shelled) organisms attached themselves to ancient sea bottoms 550 million years ago.

Just as scat and tracks provide a glimpse into the lives of today’s animals, fossils reveal the activities of the ancients. Dinosaur tracks may show a migration route and coprolites shed light on an animal’s ecology by recording what came out the other end after a meal.

When you do chance upon a fossil, look, but definitely don’t touch. Every rock packed out, from little Joey’s souvenir to the 12 tons of fossilized wood poached from Arizona’s Petrified Forest National Park every year, removes important historical and environmental information. And, points out Santucci, “fossils are nonrenewable.”

Besides, the best part of fossil hunting involves not plundering, but pondering. Says paleontologist McFarland, “Contemplate that life connection between you and some animal that lived hundreds of millions of years ago. It’s a way of putting yourself and life in perspective.”


American Association of Petroleum Geologists Geological Highway maps. Eleven regional maps note some fossil locations. Contact: (800) 364-2274;; $12 each.

The U.S. Geologic Survey’s (USGS) two-sheet Geologic Map of the United States is available for $14 (888-ASK-USGS;, and state geologic maps are $7 per sheet ( The National Atlas at, lets you create and download a map of any area of the country at the scale you want. Click on Make Maps, then select Geologic Map. Click on the Legend button below the map to see what color on the map represents each rock type.

Loriee Evans escapes to the backcountry outside her St. Louis, Missouri, home to “watch” ancient wildlife.

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