The Cambrian period is a part of the
Lower Palaeozoic (see below):
PALAEOZOIC |
UPPER
|
Permian
|
45,000,000 yrs
|
280 x 10E6
|
Carboniferous
|
65,000,000 yrs
|
345 x 10E6
|
Devonian
|
50,000,000yrs
|
395 x 10E6
|
|
LOWER
|
Silurian
|
35,000,000 yrs
|
430 x 10E6
|
Ordovician
|
70,000,000 yrs
|
500 x 10E6
|
|
|
|
Cambrian
|
70,000,000 yrs
|
570 x 10E6
|
The fourth column shows how long the period lasted,
the fifth column shows how many years from the present it was current.
The term 10E6 means one million for those of you who are not scientifically
minded.
It is not until well up into the Cambrian period that
fossil remains are found. There are schools of thought that say the
sea water of the Pre-Cambrian did not contain enough dissolved salts
to allow for secretions that make up the hard parts of animals.
So..Trilobites appeared in the Cambrian, reached their
height in the Ordovician, after which they began a slow decline and
the last known trilobites were found in rocks of Permian age on the
Isle of Timor and in the Salt Range of the Himalayas.
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