MESOGAMMARIDAE BOUSFIELD, 1977

Tomikawa, Ko, Kobayashi, Norio, Morino, Hiroshi & Mawatari, Shunsuke F., 2007, New gammaroid family, genera and species from subterranean waters of Japan, and their phylogenetic relationships (Crustacea: Amphipoda), Zoological Journal of the Linnean Society 149 (4), pp. 643-670 : 646

MESOGAMMARIDAE BOUSFIELD, 1977

Diagnosis: Mandible: molar tritulative. Maxilla 1: outer plate with ten or 11 robust serrate setae apically. Maxilliped: outer plate reaching end of palp article 1. Pereopod 7: basis not expanded. Gills: coxal gills on pereopods 2–6. Uropod 1: peduncle with or without basofacial armature. Uropod 3: inner ramus present; outer ramus elongate, uni or bi-articulate.

Type genus: Mesogammarus Tzvetkova, 1965 .

Remarks: The family was erected by Bousfield (1977) to accommodate the monotypic genus Mesogammarus Tzvetkova, 1965 . Subsequently, another monotypic genus, Paramesogammarus Bousfield, 1979 , was added to the family by Bousfield (1979). Barnard & Barnard (1983) emended the original familial diagnosis.

Our view of what constitutes the important diagnostics of this family is given above. Based on this new diagnosis, we assign Eoniphargus and Octopupilla gen. nov. to Mesogammaridae .

A potential relationship of Eoniphargus to the monotypic genus Indoniphargus Straškraba, 1967 has been suggested by several authors (e.g. Straškraba, 1967; Bousfield, 1977; Stock & Jo, 1990). By contrast, Barnard & Barnard (1983) classified Eoniphargus near the gammarids, but Indoniphargus near the melitids. In our opinion, Indoniphargus appear to belong to Mesogammaridae . The presence or not of the coxal gill 7 is a significant high-level taxonomic character ( Bousfield, 1977, 1983). But this character is not given in Chilton’s (1923) original description and Stephensen’s (1931) redescription of Indoniphargus indicus . The decision of whether Indoniphargus belongs to Mesogammaridae should be postponed until the coxal gill feature of I. indicus can be clarified.

The genera of Mesogammaridae may be further grouped into related complexes. Thus, Mesogammarus and Paramesogammarus , a marine group, posess the well-developed eyes, the stout propodus of the gnathopods, the smooth palmar margin of the gnathopods and the unstalked coxal gills. Eoniphargus and Octopupilla , a second related group, inhabit subterranean waters and possess the reduced eyes, the feeble propodus of the gnathopods, the palmar margin with small triangular protuberances and the pedunculate coxal gills.

Composition: As emended above, the family now includes the following genera: Mesogammarus Tzvetkova, 1965 , Paramesogammarus Bousfield, 1979 , Eoniphargus ( Uéno, 1955) and Octopupilla gen. nov.