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Trilobites |
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| Palæos: | |
Trilobites |
| INVERTEBRATES | Trilobita Home |
| Page Back | Unit Home | Animal Kingdom | Arthropods | Arachnomorpha | Trilobite Glossary |
| Page Next | Page Up | Cambrian Period | Paleozoic Era | Paleozoic Biota | Further Reading |
The Trilobites are an extinct group of Paleozoic marine arthropods of which 1400 genera and more than four thousand fossil species are known. They are so-called because the body is molded into 3 lobes. In addition it is divided into three segments, a head or cephalon, a thorax, and a "tail" or pygidium, each segmented.
The cephalon is composed of 5 segments, and has a pair of antennae and well-developed compound eyes. Trilobites were the first creatures to developed such advanced eyes. The thorax is composed of a number of segments. Each segment bears a pair of similar branched appendages.
Trilobites were also among the first arthropods to develop a hard easily fossilized exoskeleton. Most species were scavengers or feeders on small organisms but a few were actively carnivorous. Some types became planktonic drifters. In size trilobites ranged from a few millimeters to 30 cm or more, though the average was about 3 to 5 cm. The group had its greatest success during the Cambrian and Ordovician periods, but remained fairly well established until the Devonian. The last stragglers died out during the Permian.
Present classifications usually list about eight orders, as follows:
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Links | |
The
Semi-Compleat Trilobite - another good Trilobite site
The Paleo Project.... A
collection of Trilobites - has a really nice selection of Trilobite
photos
