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3 Annelids. 4 Molluscs. Toggle Molluscs subsection. 4.1 Gastropods. 4.2 Bivalvia. 5 Cnidaria. 6 Arthropods. ... 206 possibly extinct species, 15 extinct in the wild ...
However, it lacks some typical annelid features and has features which are not usually found in annelids and some of which are associated with other phyla. [58] Then Simon Conway Morris and John Peel reported Phragmochaeta from Sirius Passet , about 518 million years old , and concluded that it was the oldest annelid known to date. [ 1 ]
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 .
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 body is muscular and relatively solid; the coelom, the spacious body cavity found in other annelids, is reduced to small channels. The majority of leeches live in freshwater habitats, while some species can be found in terrestrial or marine environments.
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.
A cross section of a post-clitellum segment of an annelid (ringed worm); almost all segments of an annelid contain the same set of organs and parts, a pattern called metamerism. Annelids have no lungs, but rather exchange carbon dioxide and oxygen directly through the moist skin when blood reaches the extremely fine capillaries of the body ...
List of annelid families describes the taxa relationships in the phylum Annelida, which contains more than 17,000 extant species including ragworms, earthworms, ...