Page 21 - DINOSOUR ATLAS

, true fossil
The big dinosaur bones that are
excavated by paleontologists are usually
true fossils, formed by a process of
mineralization. Over millions of years,
groundwater containing dissolved
minerals seeps into bones that have
been buried by later sediments. The
minerals in the bones turn solid,
somewhat like limescale forming in pipes,
and this transforms the bones into stony
fossils. These teeth and jaws of the giant
Cretaceous hunter Tyrannosaurus rex were
preserved in this way.

trace fossil .
Some fossils do not preserve part
of the animal’s body, but show
where it has been. These can be
among the most fascinating
fossils, because they give clues to
how an animal lived. Dinosaur
trace fossils include the remains
of nests and burrows, and even
fossilized droppings called
coprolites. Some of the most
common are footprints, like this
three-toed print of a theropod.

d perfect preservation
The soft “rain” of fine sediment that
settles on lake and seabeds can
create finely detailed fossils of
animals like fish. This
freshwater perch died
over 37 million years
ago, but it has been
preserved with its
bones, skin, and
delicate fin rays intact.

fossil plant .
Plants may also be
fossilized, particularly if they are
buried in airless swamps where the waterlogged
conditions stop them from decaying. This fossil fern
dates from the Carboniferous Period, some 300 million
fossiLized skin years ago. Many similar Carboniferous plants were buried,
and fin membranes reveal compressed, and turned into the “fossil fuel” we call coal.
the true shape of the fish

flies in aMber .
Sometimes small animals are found
trapped in amber, which is tree resin
that has fossilized with age. These
insects became stuck in the gluey
resin millions of years ago, and the
resin then covered them and stopped
them from decaying. Every detail of
their fragile bodies has been preserved.

soMe soft tissues may be preserved
inside the amber, but substances
like DNA are unlikely to survive
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