Evolution—The Theory and Its Supporting Evidence - The Changing Earth: Exploring Geology and Evolution - page 487

Geo-inSight Fossilization

Although the chance that any one organism will be preserved in the fossil
record is slight, fossils are nevertheless common because so many billions of
organisms lived during the past several hundred million years. Hard skeletal
parts of organisms living where burial was likely are most common.

1. 2. The bones of this dinosaur and the shells of these marine animals called

ammonites have had minerals added to their pores, making them more durable.

3. A tiny amphibian track (left)
and a coprolite (fossilized
feces, above) from a carnivorous
mammal. The coprolite is about
5.5 cm long.

4. Trace fossils do not include actual
remains—only tracks, burrows,
nests, and droppings.

6. Fossil insect replaced by
silicon dioxide (SiO 2 ).

5. This object looks like
a clam, but it is simply
sediment that filled a
space formed when a
clam shell dissolved.

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