Annelids

Annelid Temporal range: Early Ordovician–Recent PreЄ Є O S D C P T J K Pg N
Glycera sp.
Scientific classification
Kingdom:	Animalia
Superphylum:	Lophotrochozoa
Phylum:	Annelida Lamarck, 1809
Classes and subclasses
Class Polychaeta (paraphyletic?) Class Clitellata (see below)    Oligochaeta – earthworms, etc.    Branchiobdellida    Hirudinea – leeches Class Echiura (previously a separate phylum) Class Machaeridia†

Class Polychaeta (paraphyletic?)
Class Clitellata (see below)
   Oligochaeta – earthworms, etc.
   Branchiobdellida
   Hirudinea – leeches
Class Echiura (previously a separate phylum)
Class Machaeridia†

The annelids (Annelida, from Latin anellus, "little ring"), also known as the ringed worms or segmented worms, are a large phylum, with over 17,000 extant species including ragworms, earthworms, and leeches. The species exist in and have adapted to various ecologies - some in marine environments as distinct as tidal zones and hydrothermal vents, others in fresh water, and yet others in moist terrestrial environments.

The annelids are bilaterally symmetrical, triploblastic, coelomate, invertebrate organisms. They also have parapodia for locomotion. Most textbooks still use the traditional division into polychaetes (almost all marine), oligochaetes (which include earthworms) and leech-like species. Cladistic research since 1997 has radically changed this scheme, viewing leeches as a sub-group of oligochaetes and oligochaetes as a sub-group of polychaetes. In addition, the Pogonophora, Echiura and Sipuncula, previously regarded as separate phyla, are now regarded as sub-groups of polychaetes. Annelids are considered members of the Lophotrochozoa, a "super-phylum" of protostomes that also includes molluscs, brachiopods, flatworms and nemerteans.