|
S.No.
|
Fossil
|
Example
|
Mode of formation
|
|
1
|
Unaltered
(Preservation)
|
Wooly mammoths, 25,000 years
old, ice in Siberia, mummies, insect.
|
Whole bodies are found frozen in ice.
|
|
2
|
Altered or
petrified fossils
|
Bones, shell, teeth, wood etc.
|
Replacement of organic parts by mineral
deposits is called petrification.
|
|
3
|
Coprolite
|
Coenozoic mammals
|
Faecal pellets buried in sediments.
|
|
4
|
Moulds and
Casts
|
Gastropods (Mullusca)
from Portland
|
Moulds of hardened and fossilized mud that surround an extinct individual, the burried individuals have been completely destroyed but the moulds retained true
copies of their shape.
|
|
5
|
Impressions
|
Archaeopteryx feather, leaf
|
Remains in fine grained sediments on
which organisms died.
|
|
6
|
Imprints
|
Dinosaur footprints, prints of leaf,
skin, wing etc.
|
Footprint trails, tract of
organism.
|
|
7
|
Compression
|
Plants
|
Main tissues part disappears and only the outer tough parts remains intact covering into rock.
|