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Placoderms primitive organisms
Placoderms are a kind of primitive fish wich
are now extinct.
We know that placoderms existed millions of
years ago. We also know what they looked like,
and how they lived, thanks to the fossil remains
found in the strata.
The fossil remains of the placoderms, just like
those of other primitive organisms, have been
formed through a process called fossilisation.
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How did the fossilisation process happen?
1. When a placoderm dies, it falls to the bottom
of the sea.
2. Decomposers and animals which feed on carrion
eliminate the soft parts.
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How did the fossilisation process happen?
3. The remains of the placoderm are quickly
covered by layers of sediment which are deposited
on the bottom.
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How did the fossilisation process happen?
4. As time goes by the remains of the organism
are covered by more layers of sediment, and the
sea level retreats.
5. The mineral substances of the environment
replace the organic matter of the organisms
remains that is, mineralisation takes place.
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How did the fossilisation process happen?
6. Millions of years later, erosion leaves the
fossil of the placoderm exposed.