Stephonyx Lowry & Stoddart, 1989

Lowry, J. K. & Kilgallen, N. M., 2014, A generic review of the lysianassoid family Uristidae and descriptions of new taxa from Australian waters (Crustacea, Amphipoda, Uristidae), Zootaxa 3867 (1), pp. 1-92 : 61

Stephonyx Lowry & Stoddart, 1989

( Fig. 39 )

Stephonyx Lowry & Stoddart, 1989: 521 .— Lowry & Stoddart, 2003: 284 (catalogue).— Diffenthal & Horton, 2007: 32 .— Senna & Serejo, 2007: 8, 13 (key).—Narahara, Tomikawa & Torigoe: 2012 (key).

Type species. Euonyx biscayensis Chevreux, 1908 , by original designation.

Included species. Stephonyx includes 13 species: S. arabiensis Diffenthal & Horton, 2007 ; S. biscayensis ( Chevreux, 1908) ; S. carinatus Bellan-Santini, 1997 ; S. incertus Bellan-Santini, 1997 ; S. mytilus ( Barnard & Ingram, 1990) ; S. laqueus (J.L. Barnard, 1967) ; S. normani ( Stebbing, 1888) ; S. perexcavatus Narahara, Tomikawa & Torigoe, 2012 ; S. pirloti ( Sheard, 1938) ; S. rafaeli sp. nov.; S. scutatus ( Griffiths, 1977) ; S. talismani ( Chevreux, 1919) ; S. uncinatus Senna & Serejo, 2007 .

Diagnostic description. Antenna 1 peduncle article 1 without anterodistal lobe; accessory flagellum not forming cap covering callynophore. Antenna 2 with weakly developed brush setae. Mandible molar a setose tongue with vestigial triturating area, a reduced column with a triturating surface or occasionally a raised weakly setose plate. Maxilla 1 outer plate a well developed 7/4 crown. Maxilla 2 inner plate slightly shorter than outer plate. Gnathopod 1 chelate; coxa 1 reduced, significantly shorter than coxa 2, subquadrate or tapering distally; ischium long (length 2 × to 4 × breadth) to very long (length 4 × to 6 × breadth); carpus very long (length more than 4 × breadth); propodus margins subparallel. Uropod 2 inner ramus not constricted. Telson deeply cleft .

Remarks. Only three uristid genera, Euonyx , Kyska and Stephonyx have chelate first gnathopods. Kyska differs from Euonyx and Stephonyx in having a fully developed gnathopod 1 coxa (significantly reduced in Euonyx and Stephonyx ). Stephonyx is a genus of scavengers with fully developed 7/4 crown of setal-teeth on the outer plate of maxilla 1 whereas Euonyx is a genus of ectoparasitic amphipod with strongly reduced (small) setal-teeth on the outer plate of maxilla 1.

Figures

FIGURE 39. Stephonyx biscayensis (Chevreux, 1908), female, 22 mm, AM P.35583, from southwest of Ireland, North Atlantic Ocean. Scale bars: MX1, MX2, MP, 0.2 mm; remainder, 0.5 mm.