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Trilobites are beetle-like, marine invertebrates ranging in size from 5mm to 50+cms, but commonly a few cms in length. A long, thin body with multiple legs and gills on either side is covered by an exoskeleton in three parts, covering the body (axial lobe) and legs (two pleural lobes). Trilobites are among the earliest invertebrates to be found in the geological column, in the lowest Cambrian. These early forms are advanced - including eyes - and so must have developed during the Precambrian. They developed a hard exoskeleton, made of chitin, at the start of the Cambrian. The became extinct by the end of the Permian. |
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It is suggested that the development of the eye was one factor in the evolutionary explosion at the beginning of the Cambrian.
Geopix Study Guide "Trilobites"- gives an illustrated description of trilobites;
- describes their main morphological features;
- explains how the mode of life of this extinct group can be determined.
The Study Guide contains the following pages:
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To order this CD go to the Geopix Online Store