The Haplotaxida are one of two

orders Order, ORDER or Orders may refer to: * A socio-political or established or existing order, e.g. World order, Ancien Regime, Pax Britannica * Categorization, the process in which ideas and objects are recognized, differentiated, and understood * H ...

within the

annelid The annelids (), also known as the segmented worms, are animals that comprise the phylum Annelida (; ). The phylum contains over 22,000 extant species, including ragworms, earthworms, and leeches. The species exist in and have adapted to vario ...

subclass

Oligochaeta Oligochaeta () is a subclass of soft-bodied animals in the phylum Annelida, which is made up of many types of aquatic and terrestrial worms, including all of the various earthworms. Specifically, oligochaetes comprise the terrestrial megadril ...

, the other being the Lumbriculida. No real common name exists, but they are simply referred to as haplotaxids. Given that the other

clitellata 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 ...

n annelids are embedded between and around the Haplotaxida and Lumbriculida, the traditional ''Oligochaeta'' are a

paraphyletic Paraphyly is a taxonomic term describing a grouping that consists of the grouping's last common ancestor and some but not all of its descendant lineages. The grouping is said to be paraphyletic ''with respect to'' the excluded subgroups. In co ...

assemblage. Thus, the Haplotaxida might eventually be up-ranked to subclass status within the ''Clitellata'' or an expanded Oligochaeta, with the present suborders advancing to order rank. The latter – though without merging the ''Oligochaeta'' and ''Clitellata'' – has been proposed time and again in the past, most prominently for the distinct '' Moniligastrina.''

Families

Of the four

suborder Order () is one of the eight major hierarchical taxonomic ranks in Linnaean taxonomy. It is classified between family and class. In biological classification, the order is a taxonomic rank used in the classification of organisms and recognized ...

s of Haplotaxida, two are minor lineages,

monotypic In biology, a monotypic taxon is a taxonomic group (taxon) that contains only one immediately subordinate taxon. A monotypic species is one that does not include subspecies or smaller, infraspecific taxa. In the case of genera, the term "unisp ...

family Family (from ) is a Social group, group of people related either by consanguinity (by recognized birth) or Affinity (law), affinity (by marriage or other relationship). It forms the basis for social order. Ideally, families offer predictabili ...

level. Another one, the

Tubificina ''Tubificina'' is a suborder of haplotaxid annelid The annelids (), also known as the segmented worms, are animals that comprise the phylum Annelida (; ). The phylum contains over 22,000 extant species, including ragworms, earthworms, and ...

, is sizeable and contains the aquatic

worm Worms are many different distantly related bilateria, bilateral animals that typically have a long cylindrical tube-like body, no limb (anatomy), limbs, and usually no eyes. Worms vary in size from microscopic to over in length for marine ...

s, while the fourth, the

earthworm An earthworm is a soil-dwelling terrestrial invertebrate that belongs to the phylum Annelida. The term is the common name for the largest members of the class (or subclass, depending on the author) Oligochaeta. In classical systems, they we ...

s or Lumbricina, unites the bulk of the order's families: Suborder Haplotaxina *

Haplotaxidae Haplotaxidae is a family of Earthworm, earthworms of the Haplotaxida order. Genera *''Alphadrilus'' Brinkhurst, 1988 *''Delaya'' Brinkhurst, 1988 *''Haplotaxis'' Hoffmeister, 1843 *''Hologynus'' Brinkhurst, 1988 *''Metataxis (annelid), Metataxi ...

Suborder Moniligastrina *

Moniligastridae Moniligastridae is a family of earthworm An earthworm is a soil-dwelling terrestrial invertebrate that belongs to the phylum Annelida. The term is the common name for the largest members of the class (or subclass, depending on the author) ...

Suborder

Lumbricina An earthworm is a soil-dwelling terrestrial animal, terrestrial invertebrate that belongs to the phylum Annelida. The term is the common name for the largest members of the class (biology), class (or subclass (biology), subclass, depending on ...

* Alluroididae *

Eudrilidae The Eudrilidae are a family of earthworms, mostly of Africa. One species, ''Eudrilus eugeniae'' (Kinberg, 1867), is widely distributed around the warmer parts of the world and historically cultured as the "African nightcrawler".Blakemore (2015) ...

Glossoscolecidae The Glossoscolecidae are a large family of earthworms (annelids) which has native representatives in South and Central America. The species A species () is often defined as the largest group of organisms in which any two individuals of th ...

Lumbricidae The Lumbricidae are a family of earthworms. About 33 lumbricid species have become naturalized around the world, but the bulk of the species are in the Holarctic region, from Canada (e.g. ''Bimastos lawrenceae'' on Vancouver Island) and the Unite ...

Hormogastridae Hormogastridae is a family of annelids belonging to the order Haplotaxida The Haplotaxida are one of two orders within the annelid subclass Oligochaeta, the other being the Lumbriculida. No real common name exists, but they are simply refer ...

* Ailoscolidae *

Lutodrilidae ''Lutodrilus'' is a genus of invertebrate in the Lutodrilidae family. It contains the following species: * ''Lutodrilus multivesiculatus ''Lutodrilus'' is a genus of invertebrate Invertebrates are animals that neither develop nor retain ...

Sparganophilidae ''Sparganophilus'', the only genus in the family Sparganophilidae, is a group of long, slender, limicolous (mud-dwelling) earthworms native to North America. The number of species is unknown, most of them are undescribed, throughout the contine ...

Criodrilidae The family Criodrilidae is represented by genus ''Criodrilus'' comprising limicolous (mud-dwelling) and/or aquatic earthworms endemic to the Palaearctic currently known only from Europe and Japan, respectively. Only three or four species are de ...

Ocnerodrilidae ''Ocnerodrilidae'' is a family of annelids belonging to the order Haplotaxida The Haplotaxida are one of two orders within the annelid subclass Oligochaeta, the other being the Lumbriculida. No real common name exists, but they are simply r ...

* Acanthodrilidae *

Octochaetidae Octochaetidae is a family of annelids belonging to the order Haplotaxida The Haplotaxida are one of two orders within the annelid subclass Oligochaeta, the other being the Lumbriculida. No real common name exists, but they are simply referr ...

* Exxidae *

Megascolecidae Megascolecidae is a family of earthworms native to Madagascar, Australia, New Zealand, Asia, and North America. At up to 2 meters in length, their large size distinguishes the Megascolecidae from other earthworm families. They are an essential par ...

* Microchaetidae Suborder

* Dorydrilidae *

Enchytraeidae Enchytraeidae is a family of microdrile oligochaeta, oligochaetes. They resemble small earthworms and include both terrestrial species known as potworms that live in highly organic Ecoregion#Terrestrial, terrestrial environments, as well as some ...

Naididae The Naididae (including the former family Tubificidae) are a family (biology), family of clitellate oligochaete worms like the sludge worm, ''Tubifex tubifex''. They are key components of the benthic communities of many freshwater and ocean, mar ...

(including Tubificidae) * Opistocystidae * Phreodrilidae

References

Annelid orders {{Annelid-stub

Families

See also

References