Epacanthion Wieser, 1953 Syn.

De Souza, João V. & Maria, Tatiana F., 2023, Taxonomic review of Thoracostomopsidae (Nematoda, Enoplida): state of the art, list of valid species and dichotomous keys, Zootaxa 5361 (4), pp. 463-496 : 473-474

publication ID	https://doi.org/ 10.11646/zootaxa.5361.4.2
publication LSID	lsid:zoobank.org:pub:DAB237DC-1444-4007-BCCA-CB92CBE66617
DOI	https://doi.org/10.5281/zenodo.10196963
persistent identifier	https://treatment.plazi.org/id/EA795F35-2538-FFFF-FF27-FD3055F7253C
treatment provided by	Plazi
scientific name	Epacanthion Wieser, 1953 Syn.
status

Treatment

Genus Epacanthion Wieser, 1953 Syn. View in CoL Hyalacanthion Wieser, 1959

The genus Epacanthion was erected by Wieser (1953), who suggested it as an intermediate state between two other Thoracostomopsidae genera Enoploides and Mesacanthion . Epacanthion microdentatum Wieser, 1953 was described and this author added other four species to the genus: the type species Epacanthion buetschlii ( Southern, 1914) Wieser, 1953, Epacanthion incurvatum ( Ditlevsen, 1926) Wieser, 1953 , Epacanthion durapelle ( Kreis, 1929) Wieser, 1953 and Epacanthion saveljevi ( Filipjev, 1927) Greenslade & Nicholas, 1991 . At that time, a taxonomic key was provided by Wieser (1953) including five known species. Furthermore, Wieser (1953) suggested a synonymy between Enoplolaimus crassus and Epacanthion saveljevi but Greenslade & Nicholas (1991) did not accept the synonymization and returned E. crassus to Enoploides as a valid species. Later, three new species were described: Epacanthion brevispiculum Mawson, 1956 ; Epacanthion filicaudatum Mawson, 1956 and Epacanthion flagellicauda Gerlach, 1956a . The original description of the last two species were based on single juveniles, but Mawson (1958) described male specimens of E. filicaudatum together with the description of Epacanthion brevispiculosum Mawson, 1958 . However, E. filicaudatum and E. incurvatum were later transferred to Enoploides by Greenslade & Nicholas (1991). These authors also transferred Enoploides polysetosum Jensen, 1986 to Epacanthion , claiming that this species bears short spicules, but it was not accepted by Jeong et al. (2020) who considered this species belonging to Enoploides . Inglis (1966) proposed the synonymization of Hyalacantion with Epacanthion and brought the three species of Hyalacantion ( H. multipapillatum Wieser, 1959 , H. pellucidum Ssaweljev, 1912 and H. murmanicum Ssaweljev, 1912 ) to this genus and Epacanthion oliffi Inglis, 1966 was also described. When describing Epacanthion gorgonocephalum Warwick, 1970a, the author transferred Enoplolaimus enoploidiforme ( Gerlach, 1952) Warwick, 1970a to this genus. Later, 16 species were considered as valid by Gerlach & Riemann (1974) who adequated the species epithet to comply with the rules of Latin grammar. A great contribution to this genus was made by Greenslade & Nicholas (1991) who invalidated Enoploides murmanicum ( Ssaweljev, 1912) Inglis, 1966 because it was described without illustrations and E. flagellicauda which was described based on a single juvenile, transferred two species to Enoploides as mentioned before, considered the redescription of Enoploides incurvatus Ditlevsen, 1926 made by Schuurmans Stekhoven (1946) as a new species belonging to Epacanthion and renamed it as Epacanthion stekhoveni Greenslade & Nicholas (1991) , besides described Epacanthion exploratoris Greenslade & Nicholas, 1991 . The last species described to this genus are from the current decade of this century (Lo Russo et al. 2013, Shi & Xu 2016). Shi & Xu (2016) provided an identification key with 28 valid species, including Epacanthion polysetosum ( Jensen, 1986) Greenslade & Nicholas, 1991 , described originally as Enoploides and mistakenly transferred to Epacanthion . However, according to Jeong et al. (2020) E. polysetosum must be a species belonging to Enoploides . Then, the key provided here includes 27 species.

Diagnosis modified from Smol et al. (2014): Cuticle usually smooth. Head broadly wedge or cone-shaped. Lips high, mostly striated. Inner labial setae long and inserted at base of lip flaps; outer labial and cephalic setae situated at the middle or anterior end of cephalic capsule. Cervical setae often present and can be numerous in males that exhibit sexual dimorphism. Mandibles consist of two plate-shaped columns (usually long and parallel) separated by a thin sheet of cuticle (space between columns not solid) and only connected anteriorly by a bar (an intermediate stage between Enoploides and Mesacanthion ) except for Epacanthion microdentatum of which the two mandibular plates are anteriorly united by a bar.; mandibular teeth small with gland opening at tip. Pharynx relatively long and cylindrical; cardia pyriform. Females didelphic-amphidelphic with reflexed ovaries at left side of the intestine. Males diorchic with both testes at left side of the intestine. Spicules mostly long (≥ 2.5 anal diameters) or short; gubernaculum without apophysis present or absent. Precloacal supplement present or absent. Three caudal glands, cells precaudally. Tail narrowly conical or attenuated. Marine.

Number of valid species: 27

1. Epacanthion agubernaculus Guilherme, da Silva & Esteves, 2009 (Campos Basin, Rio de Janeiro, Brazil)

2. Epacanthion ampullatum Lo Russo, Villares, Martelli, Pastor de Ward & Harguinteguy, 2013 (Rada Tilly, Argentina)

3. Epacanthion bicuspidatum Lo Russo, Villares, Martelli, Pastor de Ward & Harguinteguy, 2013 (Puerto Madryn, Argentina)

4. Epacanthion brevispiculosum Mawson, 1958 (Kerguelen Islands)

5. Epacanthion brevispiculum Mawson, 1956 ( Antarctica)

6. Epacanthion buetschlii ( Southern, 1914) Wieser, 1953 (Irish Coast of Atlantic )— type species

Syn. Enoplus buetschlii Southern, 1914

7. Epacanthion durapelle ( Kreis, 1929) Wieser, 1953 (English Channel)

Syn. Enoploides durapelle Kreis, 1929

8. Epacanthion enoploidiforme ( Gerlach, 1953) Warwick, 1970a (Mediterranean)

Syn. Enoplolaimus enoploidiformis Gerlach, 1953