Facts about trilobite fossils

Written by stephen oakley
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Facts about trilobite fossils
Trilobite fossils can display incredible detail. (Trilobite of Morocco - Period Devonian image by santosilva from Fotolia.com)

Trilobites are one of the most popular fossils studied by collectors and paleontologists alike. Living in the oceans hundreds of millions of years ago, trilobites were arthropods similar to the crabs and spiders we see today. An arthropod is an invertebrate animal with a hard outer shell known as an exoskeleton. Trilobite fossils have been found all over the world in rocks that were once part of the ancient sea bed.

Age of Trilobites

The oldest trilobite fossils date from the Cambrian geological era, over 500 million years ago. Specimens of this age have been found in Canada, Morocco, Russia, Spain and the United States. Trilobites were abundant on the earth for aeons, but became extinct before the age of dinosaurs began some 250 million years ago.

Physical Characteristics

Trilobites had a three-lobed body, which is the characteristic for which they were named. The frontal lobe or head is called the cephalon. The centre lobe or body is the thorax and the tail is known as the pygidium. This segmented body was flexible enough to allow the trilobite to roll into a ball for protection against predators. As the trilobite grew, it shed its exoskeleton periodically and grew a new one in a process called moulting. Most trilobite fossils are actually the impressions left by the discarded moults.


Many different types of trilobites roamed the ancient seas. Paleontologists have identified 10 distinct orders with more than 20,000 species. This tremendous diversity is one of the main reasons trilobites are studied so extensively around the world. Some species were tiny and would have been barely visible in water. But there were also giants. The largest trilobite fossil on record measures more than 28 inches in length and was found in Canada.

Trilobite Firsts

Scientists have discovered many interesting facts through the detailed study of perfectly preserved trilobite fossils. Trilobites were the first animal to develop compound eyes which are common in many insects today. According to Dr. Sam Gon, an internationally recognised trilobite expert, the eyes were very advanced and provided excellent depth of field with very little image distortion. They were also the first creatures to have multiple appendages that allowed them to move quickly along the sea floor.

Fossil Locations

Although trilobite fossils are common in most parts of the world, some locations are recognised for yielding specimens of exceptional quality. The Burgess Shale in the Rocky Mountains of British Columbia, Canada, has produced some of the oldest and most detailed fossils ever found. In the United States, the House Range in western Utah and Coal County, Oklahoma, produce some of the best trilobite specimens.

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