Share this credible answer with others. Simply paste this code into your blog or Web page:
The trilobites comprise a wholly extinct group of primitive marine arthropods. They were extremely abundant in the Cambrian and Ordovician geologic periods, becoming extinct in the Permian. The flattened, oval body was composed of a head covered by a dorsal shield, a trunk (thorax), and a terminal segment (pygidium). Most of the 3,900 species ranged in length from 1 to 4 in. (2.5-10 cm); some planktonic forms were smaller, and some species were as long as 2 1/2 ft (76 cm). Triarthrus eatoni was a fossil trilobite common in the Ordovician seas.
|
Answer verified with
|
HighBeam gives you access to newspaper, magazine, and trade journal articles plus press releases, facts, information, and biographies from thousands of sources.