Polychaete

Polychaetes
A variety of marine worms from Das Meer, M.J. Schleiden (1804–1881).
Scientific classification
Kingdom:	Animalia
Phylum:	Annelida
Class:	Polychaeta Grube, 1850

Polychaetes, or bristle worms, are a class of annelid worms.

They are generally found in a marine environment. There are more than 10,000 known species in this class. They are ancient animals, dating back to 518 million years ago. They are first found in the early Cambrian fossil beds of Sirius Passet in Greenland.^[1]

Each of their body segments has some fleshy protrusions that stand out. These 'parapodia' have many bristles, which are made of chitin. This is different from the Oligochaeta, which are similar in form, but only have a few bristles.

Common species are the lugworm, and the clam worm Nereis (which is sometimes also called a 'sandworm').^[2]

1. ↑ Morris S.C. & Peel J. S. 2008. The earliest annelids: Lower Cambrian polychaetes from the Sirius Passet lagerstätte, Peary Land, North Greenland. Acta Palaeontologica Polonica 53: 137. [1]
2. ↑ Barnes, Robert D. 1982. Invertebrate zoology. Philadelphia, PA: Holt-Saunders International. pp. 469–525. ISBN 0-03-056747-5.