trilobite


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trilobite

(trī`ləbīt'), subphylum of the phylum ArthropodaArthropoda
[Gr.,=jointed feet], largest and most diverse animal phylum. The arthropods include crustaceans, insects, centipedes, millipedes, spiders, scorpions, and the extinct trilobites.
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 that includes a large group of extinct marine animals that were abundant in the Paleozoic era. They represent more than half of the known fossils from the Cambrian period. The trilobite body was generally oval and flat and was divided into three roughly equal sections: the head, thorax, and tail. The name trilobite refers to a pair of furrows along the length of the animal that divided the body into three longitudinal regions. The body was covered by a mineralized shell. Because the dorsal, or upper, shell was thicker than the under shell, it has been the part best preserved in fossil form. Trilobites were abundant inhabitants of the Cambrian and Ordovician geological periods. They declined thereafter, possibly because they became food for cephalopods and later for fish, and became extinct in the Permian period. Trilobites are most closely related to the chelicerates, which include the horseshoe crabs and spiders.

Bibliography

See R. Fortey, Trilobite! Eyewitness to Evolution (2000).

trilobite

any extinct marine arthropod of the group Trilobita, abundant in Palaeozoic times, having a segmented exoskeleton divided into three parts
References in periodicals archive ?
The attachment surfaces of bryozoans are exposed on the surfaces of internal moulds of the trilobite cranidia.
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Trilobite tracks and other trace fossils from the Upper Cambrian of North Wales.
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Palaeogeographical controls on the Cambrian trilobite immigration and evolutionary patterns reported in the western Gondwana margin.
Cambrian trilobite from Canada has a smeared head and a cobweb pattern
The trilobite distribution and zonation were used in chronostratigraphic subdivision by Lamansky (1905).
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