Eoniphargus Ueno , 1955

Shintani, Aki, Lee, Chi-Woo & Tomikawa, Ko, 2022, Two new species add to the diversity of Eoniphargus in subterranean waters of Japan, with molecular phylogeny of the family Mesogammaridae (Crustacea, Amphipoda), Subterranean Biology 44, pp. 21-50 : 21

Genus Eoniphargus Ueno, 1955

Neoniphargus (Eoniphargus) Uéno, 1955: 148.

Eoniphargus : Straškraba, 1964, 136, 138; Straškraba 1967, 127; Bousfield 1977, 301; Barnard and Barnard 1983, 581-582; Holsinger 1994, 157; Tomikawa et al. 2007, 646.

Diagnosis.

Head without eyes, rostrum short, inferior antennal sinus distinct. Pleonites 1-3 with dorsal setae, lacking processes. Urosomite 2 with dorsal robust setae. Antenna 1 longer than antenna 2; accessory flagellum three- or four-articulate. Male antenna 2 with calceoli. Mandible with triturative molar with seta; left incisors five- or six-dentate; left lacinia mobilis four- or five-dentate; palp article 3 with A-, D- and E-setae. Maxilla 1 with inner plate bearing plumose setae; outer plate with 11 serrate robust setae. Inner plate of maxilla 2 with oblique row of facial setae. Gnathopods subchelate. Coxa of pereopod 4 with posterior concavity. Coxal gills with stalks, on gnathopod 2 and pereopods 3-6. Uropod 1 with basofacial robust setae on peduncle. Uropod 3 with small, scale-like inner ramus; outer ramus one- or two-articulate. Telson cleft with apical robust setae.

Type species.

Neoniphargus (Eoniphargus) kojimai Uéno, 1955, original designation.

Remarks.

Eoniphargus is morphologically similar to Octopupilla in the presence of pleonites without dorsal processes, five-dentate incisor of the left mandible, mandibular palp article 3 with A-setae, inner plate of maxilla 2 with oblique row of facial setae, stalked coxal gills, peduncle of uropod 1 with basofacial robust setae, and telson lobes tapering distally. However, Eoniphargus differs from Octopupilla in the following features (features of Octopupilla in parentheses): eyes absent (rudimentary eyes), incisor of right mandible five- to six-dentate (four-dentate), inner lobes of the lower lip absent (vestigial), and inner ramus of uropod 3 shorter than 0.3 × the outer ramus (0.7 ×). Eoniphargus also resembles Indoniphargus Straškraba, 1967, but the familial affiliation of the latter has been controversial. Tomikawa et al. (2007) and Fišer et al. (2013) included Indoniphargus in Mesogammaridae . Sidorov et al. (2018) regarded Indoniphargus as a member of Austroniphargidae Iannilli, Krapp, & Ruffo, 2011. However, since the taxonomic position of Indoniphargus is beyond the scope of this paper, it will not be discussed here further. Eoniphargus is distinguished from Indoniphargus by the presence of facial setae in an oblique row of the inner plate of maxilla 2 (absent in Indoniphargus ) and the elongate propodi of gnathopods 1 and 2 (mitten-form in Indoniphargus ).