Onisimus Boeck, 1871

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 : 45

Onisimus Boeck, 1871

( Fig. 27 )

Onisimus Boeck, 1871: 111 .— Stebbing 1906: 25.—Schellenberg 1927: 659.— Stephensen 1929: 53.— Gurjanova 1951: 161.—J.L. Barnard 1969: 352.— Barnard & Karaman 1991: 506.— Lowry & Stoddart, 1993: 168.—Vader, Johnsen & Berge, 2005: 2.

Onesimus Boeck, 1876: 161 (invalid emendationof Onisimus Boeck, 1871 ).—G.O. Sars 1891: 104.

Pseudalibrotus Della Valle, 1893: 798 .— Stebbing 1906.—33.—Schellenberg 1927: 671.— Stephensen 1929: 55 (type species: Anonyx litoralis Boeck, 1871 , monotypy).

Alibrotus Sars, 1891: 101 .

Paronesimus Stebbing, 1894: 14 .— Stebbing 1906: 43.— Gurjanova 1951: 196.— Barnard 1969: 357.— Barnard & Karaman 1991: 516 (type species: Paronesimus barentsi Stebbing, 1894 , monotypy).

Boeckosimus J.L. Barnard, 1969: 330 .— Barnard & Karaman 1991: 470 (type species: Anonyx edwardsii Krøyer, 1846 , original designation).

Type species. Anonyx litoralis Krøyer, 1845 , selected by Boeck, 1876.

Included species. Onisimus includes 26 species: O. abyssi Oldevig, 1959 ; O. affinis Hansen, 1887 ; O. barentsi ( Stebbing, 1894) ; O. birulai ( Gurjanova, 1929b) ; O. botkini Birula,1897 ; O. brevicaudatus Hansen, 1887 ; O. caspius (G.O. Sars, 1896) ; O. caricus Hansen, 1887 ; O. derjugini ( Gurjanova, 1929a) ; O. dubius Schellenberg, 1935 b ; O. edwardsii Krøyer, 1846 ; O. glacialis (G.O. Sars, 1900) ; O. krassini Gurjanova, 1951 ); O. leucopis G.O. Sars, 1879 ; O. litoralis ( Krøyer, 1845) ; O. nanseni (G.O. Sars, 1900) ; O. normani G.O. Sars, 1891 ; O. platyceras (G.O. Sars, 1896) ; O. plautus Krøyer, 1845 ; O. punctatus ( Bate, 1862) ; O. sextonae Chevreux, 1926 ; O. sibiricus Brüggen, 1909 ; O. simus Gurjanova, 1962 ; O. turgidus G.O. Sars, 1879 ; O. uschakovi ( Gurjanova, 1933) ; O. zenkevitchi Mednikov, 1960 .

Nomina nuda. Onisimus abyssicola ( Stuxberg, 1880) ; O. crassini ( Gorbunov, 1946) ; O. vorax ( Stuxberg, 1880) ; O. zebra ( Stuxberg, 1880) .

Diagnostic description. Antenna 1 peduncle article 1 without anterodistal lobe; accessory flagellum forming cap covering callynophore. Antenna 2 without brush setae. Mandible molar a column with 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 concave anterior margin; ischium short (length less than 2 × breadth); carpus short (length 1 to 2 × breadth); propodus margins slightly tapering distally. Uropod 2 inner ramus with or without constriction. Telson entire to moderately cleft.

Remarks. Based on the morphology of gnathopod 1 Onisimus and Anonyx are very similar. Onisimus retains the triturating molar characteristic of tryphosine amphipods while Anonyx has a derived setose tongue.

Figures

FIGURE 27. Onisimus edwardsi (Krøyer, 1846), female, 13.0 mm, AM P.35587, from west Greenland. Scale bars: gnathopods, pereopods, 0.5 mm; remainder, 0.2 mm.