The Haplotaxida are one of two

orders Order, ORDER or Orders may refer to: * Categorization, the process in which ideas and objects are recognized, differentiated, and understood * Heterarchy, a system of organization wherein the elements have the potential to be ranked a number of d ...

within the

annelid The annelids (Annelida , from Latin ', "little ring"), also known as the segmented worms, are a large phylum, with over 22,000 extant species including ragworms, earthworms, and leeches. The species exist in and have adapted to various ecol ...

subclass

Oligochaeta Oligochaeta () is a subclass of 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 megadrile earthworm ...

, the other being the

Lumbriculida The Lumbriculidae are a family of microdrile oligochaetes common in freshwater environments, including streams, lakes, marshes, wells and groundwater. They should not be confused with the earthworm family Lumbricidae The Lumbricidae are a fa ...

. 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, the ...

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

paraphyletic In taxonomy (general), taxonomy, a group is paraphyletic if it consists of the group's most recent common ancestor, last common ancestor and most of its descendants, excluding a few Monophyly, monophyletic subgroups. The group is said to be pa ...

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 suborders 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 "unispec ...

family Family (from la, familia) is a Social group, group of people related either by consanguinity (by recognized birth) or Affinity (law), affinity (by marriage or other relationship). The purpose of the family is to maintain the well-being of its ...

level. Another one, the

Tubificina ''Tubificina'' is a suborder of haplotaxid annelid worms. References Protostome suborders {{Annelid-stub ...

, is sizeable and contains the aquatic

worms Worms may refer to: *Worm, an invertebrate animal with a tube-like body and no limbs Places *Worms, Germany Worms () is a city in Rhineland-Palatinate, Germany, situated on the Upper Rhine about south-southwest of Frankfurt am Main. It had ...

, while the fourth, the

earthworm An earthworm is a terrestrial invertebrate that belongs to the phylum Annelida. They exhibit a tube-within-a-tube body plan; they are externally segmented with corresponding internal segmentation; and they usually have setae on all segments. Th ...

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

Haplotaxidae Haplotaxidae is a family of earthworms of the 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 referred to as hapl ...

Suborder Moniligastrina *

Moniligastridae Moniligastridae is a family of earthworms An earthworm is a terrestrial invertebrate that belongs to the phylum Annelida. They exhibit a tube-within-a-tube body plan; they are externally segmented with corresponding internal segmentation; a ...

Suborder

Lumbricina An earthworm is a terrestrial invertebrate that belongs to the phylum Annelida. They exhibit a tube-within-a-tube body plan; they are externally segmented with corresponding internal segmentation; and they usually have setae on all segments. Th ...

Alluroididae Alluroididae 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 referre ...

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 '' Pontoscolex corethrurus'' has a circumtropical distribution. They are found mostly in forest, but one ...

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 Uni ...

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 Invertebrates are a paraphyletic group of animals that neither possess nor develop a vertebral column (commonly known as a ''backbone'' or ''spine''), derived from the notochord. This is a groupin ...

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 contin ...

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 The Acanthodrilidae are an ancient and widely distributed family of earthworms which has native representatives in Australia, New Zealand, South Africa, South America, and North America. No native species are known from India (cf. Octochaetida ...

Octochaetidae Octochaetidae is a family of annelids The annelids (Annelida , from Latin ', "little ring"), also known as the segmented worms, are a large phylum, with over 22,000 extant species including ragworms, earthworms, and leeches. The species exi ...

* Exxidae *

Megascolecidae The Megascolecidae is a taxonomic family of earthworms which is native to Madagascar, Australia, New Zealand and both South East Asia and North America. All species of Megascolecidae belong to the Clitellata class. Megascolecidae are a large fami ...

* Microchaetidae Suborder

Tubificina ''Tubificina'' is a suborder of haplotaxid annelid worms. References Protostome suborders {{Annelid-stub ...

Dorydrilidae Dorydrilidae 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 referre ...

Enchytraeidae Enchytraeidae is a family of microdrile oligochaetes. They resemble small earthworms and include both terrestrial species known as potworms that live in highly organic terrestrial environments, as well as some that are marine. The peculiar genu ...

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

(including Tubificidae) *

Opistocystidae Opistocystidae 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 ...

* Phreodrilidae

Families

See also