Two new species add to the diversity of Eoniphargus in subterranean waters of Japan, with molecular phylogeny of the family Mesogammaridae (Crustacea, Amphipoda) Author Shintani, Aki Graduate School of Humanities and Social Sciences, Hiroshima University, 1 - 1 - 1 Kagamiyama, Higashihiroshima, Hiroshima, 739 - 8524, Japan Author Lee, Chi-Woo https://orcid.org/0000-0002-0763-4271 Nakdonggang National Institute of Biological Resources, 137, Donam 2 - gil, Sangju-si, Gyeongsangbuk-do, 37242, Republic of Korea Author Tomikawa, Ko Graduate School of Humanities and Social Sciences, Hiroshima University, 1 - 1 - 1 Kagamiyama, Higashihiroshima, Hiroshima, 739 - 8524, Japan tomikawa@hiroshima-u.ac.jp text Subterranean Biology 2022 2022-08-15 44 21 50 http://dx.doi.org/10.3897/subtbiol.44.86914 journal article http://dx.doi.org/10.3897/subtbiol.44.86914 1314-2615-44-21 1865B08110724900BFC7563C0D29DA7D 27097103DFA85FF0954CAADE72F24005 Genus Eoniphargus Ueno , 1955 Neoniphargus (Eoniphargus) Ueno , 1955: 148. Eoniphargus : Straskraba , 1964, 136, 138; Straskraba 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 Ueno , 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 x the outer ramus (0.7 x ). Eoniphargus also resembles Indoniphargus Straskraba , 1967, but the familial affiliation of the latter has been controversial. Tomikawa et al. (2007) and Fiser 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 ).