Wanted: Oscar Obsidian - Auckland Museum

Background
WHAT ARE FOSSILS?
Most fossils are the preserved hard parts of
plants or animals, such as wood, shells, bones and
teeth. Less common are the traces of soft parts
like leaves and soft tissues. Some fossils show
where an animal has been, such as footprints and
worm trails. Fossils are found in sedimentary rocks
in many parts of New Zealand, from sea level to
mountain tops.
When an animal or plant dies, its soft parts are
usually eaten by scavengers or decay rapidly.
The hard parts may be buried by soil, mud, or
sand, which protects them from further decay or
damage.
Many layers of sediment may accumulate on top.
Eventually, they harden into rock.
Auckland Museum 15
Forces deep within the earth may fold or tilt the
rock and push some of them up to form land and
mountains.
We find fossils in cliffs and road cuttings where
natural erosion or bulldozers have exposed layers
of rock.
Animal and plant remains may be preserved as
fossils in a number of ways:
Shells and skeletons - The most common fossils are
an animal's hard skeletal parts composed of bone
or shell. These can remain virtually unchanged in
the rock.
Mummification - When both the hard and soft
parts of an animal is preserved, it is called mummification.
Some examples are the mummified
remains of moa in caves, the freezing of mammoths
in ice, or the complete preservation of
insects in gum.
Petrification - Dissolved minerals that seep slowly
through rock often add to or replace the original
fossil. This gradual process often increases the
fossil's weight and hardness and literally turns it to
stone.