Trilobites
Trilobites belong to the group of Arthropods. Trilobites are the oldest known animals with eyes. They occur in sediments from the Cambrian  period and became extinct at the end of the Permian period in the Paleozoic . The name is because of the three lob configuration of the skeleton. They have two pleural lobes, and one axial lobe in the middle. Three parts can be distinguished in trilobites: the cephalon (head), the thorax (body) and pygidium (tail).
The armour of trilobites was made of Chitin. Because of the hard armour, trilobites had to shed their skin regularly. That is why separate heads and tail parts are found.
Elrathia kingii, middle-Cambrian, Wheeler formation, Utah USA. Photo: © Tomas Hekkers
Some trilobites on or close to the seafloor. They lived of plankton, and other small organisms. The size varies between several millimetres up to 72 centimetres (New Foundland, Isotelus rex). New (sub)species are still found. The shape of trilobites can vary. There were species with or without spines, blind species, or trilobites with large eyes. Trilobites have facet eyes, which have sometimes been beautifully preserved in the fossils.
Whole trilobites can be found as fossil, but also the separate parts of the skeleton, or the walking tracks of trilobites (cruziana). The tracks are footprints, and the tracks where the animals dug into the bottom. Only the skeletal parts of the trilobites have been preserved.
Example of a trilobite track (Cruziana).
Trilobites can be found in many countries. The main areas known for its trilobites are the Chech Republic, Morocco, and the USA. In Europe you can also find trilobites in the UK, Germany, Sweden, Estonia, and Belgium.
In the phylum Arthropoda the class of Trilobita can be subdivided into nine orders. The Phacopida are best known, with the species Phacops. The nine orders are subdivided in 150 families, with in total more than 15000 described species.
 Click here for information where to find these fossils.
 Go to the Photo page to view photographs of Trilobites. |
