Definition of Annelida in US English:


plural noun

  • A large phylum that comprises the segmented worms, which include earthworms, lugworms, and leeches.

    • ‘For the first time, GHF9 cellulases were recognized in two new animal phyla, in Annelida and Echinodermata (sea urchin).’
    • ‘Segmented worms or Annelida, Latin for little rings, are all seen on the reefs too.’
    • ‘Some molecular phylogenies place Sipuncula with Annelida, a grouping that implies that molluscan cross pattern of early spiral cleavage evolved several times independently.’
    • ‘The initiating embryological tissue varies a good bit within the Annelida, and even between adult and larval segments.’
    • ‘Based on the available data, both McHugh and Rouse and Fauchald recommended that the Glade revert to its original nomen, Siboglinidae, within the Annelida.’
    • ‘The two largest groups of trochozoans are the Mollusca and the Annelida (segmented worms).’
    • ‘The term Polychaeta may no longer be valid because Polychaeta is likely a synonym for Annelida.’
    • ‘They are members of the phylum Annelida, the group that includes segmented worms such as leeches, tube worms, and the familiar earthworm.’
    • ‘Indeed, a few Vendian fossils, such as Spriggina, were once assigned to the Annelida; however, this identification is now doubted.’
    • ‘These comparisons strongly support the closer relationship of Sipuncula with Annelida, to the exclusion of Mollusca and other taxa.’
    • ‘It is possible that Annelida may not share with many other animals the potential to use a variety of alternative initiation codons.’
    • ‘The lower metazoan groups Gastrotricha and Gnathostomulida, but also Onychophora, Annelida, Mollusca, and Enteropneusta would be the most relevant taxa.’
    • ‘Analyses including a variety of annelids and molluscs do not show Annelida and Mollusca as monophyletic, and the Ectoprocta are usually polyphyletic too.’
    • ‘Echiurans were included in the Annelida until recently, and they are still considered close relatives of the annelids.’
    • ‘One of the two vascular hemoglobins possesses a hexagonal-bilayer hemoglobin (HBL-Hb) quaternary structure, which is only found in the Annelida and Vestimentifera.’
    • ‘The gut pH of Arenicola marina ranges from 5.4 to 7.0 and is fairly typical for the Annelida, although the pH for other groups can be more extreme.’
    • ‘Over the past 100 years, evolutionary origins of siboglinids, echiurids, myzostomids, and sipuculans have all been related to Annelida.’
    • ‘Click on the buttons below to learn more about the Annelida.’
    • ‘Two phyla that are probably close relatives of the Annelida, the Pogonophora and Echiura (spoon worms) are very rare as fossils, but all three groups belong to the larger group Trochozoa.’
    • ‘Cycloneuralia may belong within the Ecdysozoa, including all molting invertebrates, while the Gnathifera are more closely related to either Platyhelminthes or Annelida.’


Modern Latin (plural), from French (animaux) annelés ‘ringed (animals)’, from Old French anel ‘a ring’, from Latin anellus, diminutive of anulus ‘a ring’.