Page 15 - The Dinosaur Book and Other Wonders of the Prehistoric World (DK-Smithsonian)

Trace fossil
Fossils that record an organism’s
activity—such as footprints,
burrows, nests, or droppings—are Fish fossil
known as trace fossils. Fossil
footprints help us understand
how animals moved.
This cast fossil Mineralization
replicates a
trilobite’s shape. Most fossils involve a process called
mineralization. Water seeping through the Types of fossils
sediment dissolves remains such as bone and
Archosaur footprint deposits crystallized rock minerals in their
Mold place, slowly turning the bones to rock.
Mold fossils form in the same
way as casts, but they preserve
an imprint of the body rather
than a replica of its shape.
Trilobites were common sea
creatures that grew by shedding
their outer skeletons, leaving
millions of fossils behind.

Trilobite mold
This mold fossil
preserves an impression
of a trilobite’s body. Petrified tree
Amber
A few fossils preserve the Petrification
whole body of a prehistoric Whole tree trunks can be fossilized
animal. Amber is a transparent by a process called petrification, which
yellow material formed preserves minute details. First, groundwater
from fossilized tree resin. It seeping through buried wood deposits
sometimes contains tiny animals crystals of silica inside tiny spaces. Then,
that became trapped in the sticky more slowly, minerals gradually replace the
resin as it oozed from a tree. wood fibers, turning the trunk to stone.
Prehistoric fly in amber

Erosion finally reveals
Millions of the fossil, allowing
years later, the paleontologists to
continents have Glaciers or other excavate it.
moved and the processes erode
dinosaur fossil the ground,
is no longer wearing away the
under the sea. sedimentary rock.
Water seeping
through the
layers replaces the
bones with rock
minerals, turning
the fossil to rock.
Bones turn to rock Continents move Erosion of surface Discovery

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