Polychaeta is a paraphyletic class of generally marine annelid worms, commonly called bristle worms or polychaetes. 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 are described in this class. Common representatives include the lugworm and the sandworm or clam worm Alitta.
The Trochozoa are a proposed Lophotrochozoa clade that is a sister clade of Bryozoa and Platyzoa. The clade would include animals in five phyla: the Nemertea, the Annelida, the Mollusca, and the two Brachiozoan phyla, Brachiopoda and Phoronida. Both annelids and molluscs have been suggested as the sister group of Brachiozoa. It has also been proposed that nemerteans are actually a clade of annelids.
Lophotrochozoa is a clade of protostome animals within the Spiralia. The taxon was established as a monophyletic group based on molecular evidence. The clade includes animals like annelids, molluscs, bryozoans, and brachiopods.
The lophophore is a characteristic feeding organ possessed by four major groups of animals: the Brachiopoda, Bryozoa, Hyolitha, and Phoronida, which collectively constitute the protostome group Lophophorata. All lophophores are found in aquatic organisms.
The Clitellata are a class of annelid worms, characterized by having a clitellum – the 'collar' that forms a reproductive cocoon during part of their life cycles. The clitellates comprise around 8,000 species. Unlike the class of Polychaeta, they do not have parapodia and their heads are less developed.
The Spiralia are a morphologically diverse clade of protostome animals, including within their number the molluscs, annelids, platyhelminths and other taxa. The term Spiralia is applied to those phyla that exhibit canonical spiral cleavage, a pattern of early development found in most members of the Lophotrochozoa.
Rhodine is a genus of capitellid segmented worms in the family Maldanidae.
Errantia is a diverse group of marine polychaete worms in the phylum Annelida. Traditionally a subclass of the paraphyletic class Polychaeta, it is currently regarded as a monophyletic group within the larger Pleistoannelida, composed of Errantia and Sedentaria. These worms are found worldwide in marine environments and brackish water.
Arenicolidae is a family of marine polychaete worms. They are commonly known as lugworms and the little coils of sand they produce are commonly seen on the beach. Arenicolids are found worldwide, mostly living in burrows in sandy substrates. Most are detritivores but some graze on algae.
The annelids, also known as the segmented worms, comprise a large phylum called Annelida. It contains over 22,000 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.
Flabelligeridae is a family of polychaete worms, known as bristle-cage worms, notable for their cephalic cage: long slender chaetae forming a fan-like arrangement surrounding the eversible head. Unlike many polychaetes, they also have large, pigmented, complex eyes.
Siphonostomites hesionoides is a species of polychaete annelid known only from subtidal lagoon deposits from the Early Eocene of Monte Bolca, Verona, Italy.
Tomopteridae is a family of holopelagic polychaetes belonging to the order Phyllodocida. The genus Tomopteris consist of about 70 species, and the three other genera of one known species each. Length varies from just 1-2 cm to 30 cm. These are very active swimmers, and have some of the highest metabolic rate among annelids. To increase buoyancy they have a large body cavity (coelom) filled with body fluid of a density similar to seawater. With the coelom taking up much of the inner space, the muscular system has been reduced to a mesh just below the epidermis. The circulatory system has been lost, and the coelomic fluid has taken over the role of transporting oxygen, nutrients and gametes. Instead of a heart the inner surface of the worm is covered with cilia that moves the fluid around inside the body. The absence of septa between the segments makes the circulation more efficient. A series of extretory organs called metanephridia consists of ciliated funnels which opens to the coleomic cavity and connects with the exterior though a nephridiopore. Some species are bioluminescent, and produce a yellow light.
Maldanidae is a family of more than 200 species of marine polychaetes commonly known as bamboo worms or maldanid worms. They belong to the order Capitellida, in the phylum Annelida. They are most closely related to family Arenicolidae, and together form the clade Maldanomorpha.
Rhodininae is a subfamily of marine polychaete worms in the family Maldanidae.
Lumbriclymeninae is a subfamily of marine polychaete worms in the family Maldanidae.
Notoproctus is a genus of marine polychaete worms in the family Maldanidae. It is the only member of the subfamily Notoproctinae.
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 and all the descendants of that ancestor. Most groups in the Clade find their ancestors within the Cambrian explosion when Annelid diversity expanded dramatically. The Pleistoannelida clade covers a variety of traits. However, the evolution of simple to complex eyes, developed papillae for burrowing, and for some specialized radioles for feeding can be seen universally across every species. New findings have discovered the range of Annelid diversity have led to uncertainty if groups with developed ancestral traits should remain within the clade. Furthermore, there's been a lack of recently discovered Annelid traits being used in the categorization of groups within the clade, leading to many hypothesis on how to do so and which should remain within the clade. Currently three smaller clades that were originally a part of the groups Errantia and Sedentaria have been proven to fall outside while still being connected to the basal groups.
Orbiniida is an order of small polychaete worms in the phylum Annelida. It is the earliest diverging clade in Sedentaria. Along with Protodriliformia, this order is composed of meiofaunal marine worms formerly known as "archiannelids". These worms inhabit the marine interstitial ecosystem, the space between sand grains.
Protodriliformia is a clade of small marine polychaetes, comprised by the groups of meiofaunal interstitial worms Protodrilida and Polygordiidae, formerly considered "archiannelids". It is the most basal clade of Errantia.
