Tmetonyx Stebbing 1906

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 : 78-80

Tmetonyx Stebbing 1906

( Fig. 48 )

Hoplonyx Sars, 1891: 91 (homonym, Coleoptera ).— Stebbing, 1894: 9.

Tmetonyx Stebbing 1906: 73 (new name).—J.L. Barnard, 1969: 365.— Barnard & Karaman, 1991: 441 (key), 535.

Type species. Oniscus cicada O. Fabricius, 1780 , original designation.

Included species. Tmetonyx includes 8 species: T. acuta (G.O. Sars, 1891) ; T. albida (G.O. Sars, 1891) ; T. cicada (O. Fabricius, 1780) ; T. gulosa ( Krøyer, 1845) ; T. leucophthalma (G.O. Sars, 1891) ; T. nardonis ( Heller, 1867) ; T. palpiserrata Bellan-Santini, 1985 ; T. rotundata (Chevreux, 1926a) ; T. similis (G.O. Sars, 1891) .

Diagnostic description. Antenna 1 peduncle article 1 without anterodistal lobe; accessory flagellum with an elongate article 1 (at least twice as long as article 2) partially covering callynophore. Antenna 2 with weakly developed brush setae. Mandible molar a reduced column with convex, fully triturating surface. Maxilla 1 outer plate a well developed 7/4 crown. Maxilla 2 inner plate significantly shorter than outer plate. Gnathopod 1 subchelate; coxa 1 large, about as long as coxa 2, subrectangular with straight anterior margin; ischium long (length 2 × to 4 × breadth); carpus long (length 2 to 4 × breadth); propodus margins subparallel. Uropod 2 inner ramus not constricted. Telson deeply cleft .

Remarks. Based on the subchelate gnathopod 1 with a fully developed coxa and long carpus Tmetonyx appears to be similar to Anonyx and Caeconyx . Tmetonyx differs from Anonyx in the accessory flagellum cap (present in Anonyx and Caeconyx ), the mandibular molar (setose with a vestigial triturating surface in Anonyx and Caeconyx ), gnathopod 1 ischium (short in Anonyx and Caeconyx ).

Distribution. Atlantic Ocean: North Atlantic; North Polar Sea; Mediterranean Sea.

Figures

FIGURE 48. Tmetonyx cicada (O. Fabricius, 1780), syntype male, 16.9 mm, female, 18.1 mm, ZMUC CRU-6032; habitus from male, 14.5 mm, AM P.38309; western Greenland. Scale bars: gnathopods, pereopods, 1.0 mm; remainder, 0.2 mm.