TRILOBITES
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Trilobites From Utah
Trilobites From Morocco
Trilobites are an extinct group of Paleozoic arthropods, somewhat like crustaceans (i.e. crabs, lobsters, etc.). There closest living relatives today are horseshoe crabs. They are found in the fossil record from the Cambrian, right through to the Permian. Trilobites were very common in both the Cambrian and Ordovician, becoming less so till their extinction in the Permian. Trilobites varied in size from a few millimetres in length, up to about 65 cm. Trilobites are characterised by their exoskeleton, which is divisible into three sections or lobes, which run the length of the trilobite from head to tail. The name tri-lob-ite is derived from this particular feature. Many arthropods, for example the insects, have a skeleton composed of chitin and organic material related to cellulose. Trilobites, however, possessed an exoskeleton which was composed of calcite in life.