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Many annelids move by peristalsis (waves of contraction and expansion that sweep along the body), [8] or flex the body while using parapodia to crawl or swim. [39] In these animals the septa enable the circular and longitudinal muscles to change the shape of individual segments, by making each segment a separate fluid-filled "balloon". [ 8 ]
The annelids, collectively called Annelida, are a large phylum of animals, comprising the segmented worms, with about 15 000 modern species including the well-known earthworms and leeches The main article for this category is Annelid .
Oligochaetes are well-segmented worms and most have a spacious body cavity (coelom) used as a hydroskeleton.They range in length from less than 0.5 mm (0.02 in) up to 2 to 3 metres (6.6 to 9.8 ft) in the 'giant' species such as the giant Gippsland earthworm (Megascolides australis) and the Mekong worm (Amynthas mekongianus).
Pleistoannelida is a group of annelid worms that comprises the vast majority of the diversity in phylum Annelida.Discovered through phylogenetic analyses, it is the largest clade of annelids, comprised by the last common ancestor of the highly diverse sister groups Errantia and Sedentaria (Clitellata and related polychaetes) and all the descendants of that ancestor.
The prostomium (From Ancient Greek, meaning "before the mouth"; pl.: prostomia; sometimes also called the "acron") is the cephalized first body segment in an annelid worm's body at the anterior end. It is in front of (but does not include) the mouth, being usually a small shelf- or lip-like extension over the dorsal side of the mouth.
Polychaeta (/ ˌ p ɒ l ɪ ˈ k iː t ə /) is a paraphyletic [1] class of generally marine annelid worms, commonly called bristle worms or polychaetes (/ ˈ p ɒ l ɪ ˌ k iː t s /). Each body segment has a pair of fleshy protrusions called parapodia that bear many bristles, called chaetae, which are made of chitin. More than 10,000 species ...
These three genera have the following characters in common. The body is small and resembles polychaete larvae; the epidermis is ciliated; the number of segments varies from five and up, or can be completely absent; small prostomium with or without appendages; parapodia absent; septa reduced or absent; the nervous system consists of a brain and longitudinal ventral nerve cords closely connected ...
This list of prehistoric annelids is an attempt to create a comprehensive listing of all genera that have ever been included in Annelida which have been found ...