Fascinating
Fossils!
Palaeontology is the scientific study of prehistoric
life. It includes the study of fossils to determine
organisms’ evolution and interactions with each
other and their environments.
Fossils are the remains or impression of a prehistoric
plant or animal embedded in rock and preserved
in petrified form. Petrified means that the organic
matter has been changed into a stony substance –
the fossilised parts are chemically altered. The word
‘fossil’ comes from the Latin word fossilis, which
means ‘dug up’.
In order for remains to become fossilised, it requires
specific conditions, which often includes quick
and permanent burial, protecting the remains
from disturbance from the environment or other
animals; a lack of oxygen, limiting decaying and
rotting of the remains; and the absence of heat or
compression, which might otherwise destroy it.
There have been fossils
found all over the world,
and there are different types
of fossils. The type of fossil
depends on how it was
created:
Natural Mould
This is when the plant or
animal rots and decays away,
leaving an imprint in the rock.
Because of this, often fossils are preserved within
sediments (matter which settles to the bottom
of liquids such as sand, silt and mud) as these
conditions occur more frequently there, and
because the majority of the Earth’s surface is
covered in water (over 70%!)
Fossils can tell us all sorts of information about the
animal – how big it was, how it died and even what
it ate!
Trace fossils
These can be footprints,
coprolites (animal poo)
or nests.
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The animal dies, and it is washed
downstream, where it rests on layers
of soft mud and is rapidly buried.
Over time, the skeleton is buried
further and further by more sediment.
The weight of all the new sediment
squashes the underlying sediment,
pressing the grains together, pushing
the water out and slowly turning the
soft sediment into hard rock (this is
called lithification).
Petrified
Petrifaction or petrification
is the process by which
organic material is converted
into stone through the
replacement of the original
material and the filling of
the original pore spaces with
minerals.
Total Preservation
This is when the whole
animal or plant is completely
preserved, such as in amber.
The process of
fossilisation
Once buried, the soft tissue and flesh
are broken down by bacteria, leaving
just the skeleton behind.
Semi-Preservation
This occurs when the soft
tissues of the organism decay
and only the hard parts of the
animal or plant are preserved
unchanged.
Natural Cast
When the mould is formed, as
in the natural mould process,
but the imprint is filled by
natural substances, such as
flint.
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Minerals contained in the sediment
replace the minerals in the skeleton
and fill any gaps as parts of the
skeleton dissolve (this is called
permineralisation).
Many millions of years may pass, but
then extreme weather can erode the
rock, revealing the fossilised skeleton.
A person who studies dinosa
urs is called
a Palaeontologist (pay-lee-on
-tol-o-jist)
The first dinosaur in space wa
s the fossil
of the Maiasaura, which was
taken on a
space shuttle mission in 1985
.
The first humans on earth are
thought to have evolved around
65 million years after dinosaurs
became extinct.
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