The Haplotaxida are one of two
orders 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
clitellatan 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 ...
at
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, 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
Suborder Moniligastrina
*
Moniligastridae
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
*
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
*
Hormogastridae
*
Ailoscolidae
*
Lutodrilidae
*
Sparganophilidae
*
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
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Acanthodrilidae
*
Octochaetidae
*
Exxidae
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Megascolecidae
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Microchaetidae
Suborder
Tubificina
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Dorydrilidae
*
Enchytraeidae
*
Naididae (including Tubificidae)
*
Opistocystidae
*
Phreodrilidae
See also
*
*
References
Annelid orders
{{Annelid-stub