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Proboscisless leeches
	A giant Americobdella species from southern Chile.
Scientific classification
Domain:	Eukaryota
Kingdom:	Animalia
Phylum:	Annelida
Clade:	Pleistoannelida
Clade:	Sedentaria
Class:	Clitellata
Subclass:	Hirudinea
Infraclass:	Euhirudinea
Order:	Arhynchobdellida; Blanchard, 1894
Suborders
	Erpobdelliformes; Hirudiniformes; and see text
Synonyms
	Arhynchobdellae Stuart, 1982[verification needed]; Pharyngobdellae; Pharyngobdellida Johnson, 1913

Arhynchobdellida, the proboscisless leeches, are a monophyletic order of leeches. They are defined by the lack of the protrusible proboscis that defines their sister taxon, the Rhynchobdellida.^[1]^[2]^[3] Arhynchobdellida is a diverse order, compromising both aquatic and terrestrial, besides sanguivorous and predatory, leeches.^[3] The order is divided into two suborders, Erpobdelliformes and Hirudiniformes (sometimes also called the Pharyngobdelliformes and Gnathobdelliformes, respectively).^[1]

Taxonomy

Historically, the Arhynchobdellida were split into two orders, the Gnathobdellida and the Pharyngobdellida.^[4] The Gnathobdellida were jawed and carnivorous or parasitic while the Pharyngobdellida were jawless and carnivorous.^[5]^[6] Current taxonomy accepts the order Arhynchobdellida and divides into two suborders. There are 215 species of Arhynchobdellid leech, in 47 genera and 13 families.^[7] The placement of Americobdellidae is uncertain; it has rudimentary jaws and is terrestrial.

Erpobdelliformes

Erpobdelliformes are jawless predators of aquatic invertebrates of varying sizes, including insect larvae, mollusks, and other annelids.^[8]^[9] Unlike other leeches, they do not penetrate the skin of hosts; and are not at all parasitic.^[10]^[11] The pharynx is spirally twisted and very large to allow for large prey; it can constitute up to one third of the leech's body length.^[1]

Hirudiniformes

Hirudiniformes are a diverse suborder defined by the presence of toothed jaws.^[1]^[11]

Cladogram

Hirudinea

Arhynchobdellida

Erpobdelliformes	Americobdellidae ? Terrestrial, jawed*, carnivorous

	Erpobdellidae Aquatic, jawless, carnivorous

	Salifidae Aquatic, jawless, carnivorous

Hirudiniformes	Americobdellidae ? Terrestrial, jawed*, carnivorous

	Cylicobdellidae Terrestrial, jawed, carnivorous

	Haemadipsidae Terrestrial, jawed, almost all sanguivorous

	Haemopidae Semi-aquatic, jawed, sanguivorous

	Hirudinidae Terrestrial, jawed, carnivorous

	Macrobdellidae

	Praobdellidae Aquatic, jawed, sanguivorous

	Semiscolecidae

	Xerobdellidae Terrestrial, jawed, sanguivorous