Thrombasia evalina, Kilgallen & Lowry, 2014

Kilgallen, N. M. & Lowry, J. K., 2014, The Tryphosa group (Crustacea: Amphipoda: Lysianassoidea: Lysianassidae: Tryphosinae), Zootaxa 3768 (5), pp. 501-545 : 525-528

Thrombasia evalina sp. nov.

( Figs 14–16 )

Types. Holotype female, 9.8 mm, AM P.69059, from east of Broken Bay , New South Wales, Australia (33°37’S 152°04’E to 33°39’S 152°02’E), 896–923 m, dredge, 10 December 1980, R. T. Springthorpe, FRV Kapala stn K80- 20-09 . Paratypes: 1 male, 10.2 mm, AM P.69060; 2 specimens, 8.0– 8.8 mm, AM P.69061, same collection details as holotype.

Additional material examined. 2 specimens, AM P.69062, from north-east of Port Jackson , New South Wales, Australia (33°41'S 152°00'E to 33°44’S 151°57’E), 820–888 m, beam trawl, 11 February 1986, R. T. Springthorpe, FRV Kapala stn K86-01-07; 1 specimen, AM P.69058, from east of Broken Bay , New South Wales, Australia (33°31’S 152°08’E to 33°33’S 152°07’E), 914 m, 2.5 m sled dredge, 10 December 1980, R. T. Springthorpe, FRV Kapala stn K80-20-08.

Type locality. Australia, New South Wales, east of Broken Bay (33°37' S 152°04' E), 896–923 m.

Etymology. Named for schooner Evalina lost in 1871 on route between Sydney and Port Stephens; used as a noun in apposition.

Description. Based on holotype, female, 9.8 mm, AM P.69059. Head lateral cephalic lobe subtriangular, apically subacute. Antenna 1 accessory flagellum forming cap partially covering callynophore; primary flagellum with strong 2-field callynophore, robust setae absent from proximal articles; calceoli absent. Antenna 2 peduncular articles 3–5 not enlarged, articles 4–5 with weak brush setae on anterior margin; calceoli absent. peduncular articles 3–5 enlarged, article 4 slightly enlarged; articles 4 and 5 with weak brush setae; flagellum long, calceoli present. Labrum, epistome and upper lip separate; epistome less produced than upper lip, straight; upper lip produced, strongly rounded apically. Mandible molar columnar, with oval fully triturating surface. Maxilla 1 outer plate setaltooth 7 cuspidate distally; palp distal margin with apical robust setae. Maxilliped outer plate with one slender and one broad apical robust setae.

Pereonites 1–7 dorsally smooth. Gnathopod 1 subchelate; coxa reduced, significantly shorter than coxa 2 (~ 50%), tapering distally; basis densely setose along anterior margin; carpus long, longer than propodus, without posterior lobe; propodus small, margins subparallel, sparsely setose along posterior margin, palm moderately acute, entire, straight. Gnathopod 2 propodus palm transverse, slightly convex. Pereopod 5 basis longer than broad, not posteroproximally excavate, posterior margin not serrate. Pereopod 7 basis posterodistally produced less than halfway along merus.

Pleonite 3 without mid-dorsal carina, not produced dorsodistally. Epimeron 3 posterior margin smooth, posteroventral corner broadly rounded. Urosomite 1 not projecting over urosomite 2. Uropod 2 inner ramus with constriction. Uropod 3 stout; inner and outer rami well developed, outer ramus article 2 short, without plumose setae. Telson moderately cleft, with 3 dorsal robust setae per lobe and 1 apical robust setae on each lobe.

Sexually dimorphic characters. Based on paratype, male, 10.2 mm, AM P.69060. Antenna 1 calceoli present. Antenna 2 peduncular article 3 enlarged, article 4 slightly enlarged; articles 4 and 5 with weak brush setae; flagellum long, calceoli present. Uropod 3 rami with dense plumose setae.

Habitat. Not recorded.

Depth range. 820–923 m (this study).

Remarks. Thrombasia evalina appears to be quite similar to T. rotundata (K.H. Barnard) . Although that species is poorly described, it shares a number of characters in common with T. evalina , notably the shortened and strongly tapering gnathopod 1 coxa and the distinctly subchelate gnathopod 2. However, the epimeron 3 posteroventral corner of T. evalina is much more broadly rounded than that of T. rotundata and the gnathopod 1 palm is straight in T. evalina but slightly convex in T. rotundata .

Distribution. Tasman Sea. Coast of New South Wales, Australia (this study).

Figures

FIGURE 14. Thrombasia evalina sp. nov. paratype, male, habitus, 10.2 mm, AM P.69060, from east of Broken Bay, New South Wales, Australia. Scale bars: 0.1 mm.

FIGURE 15. Thrombasia evalina sp. nov. paratype, male, 10.2 mm, AM P.69060, from east of Broken Bay, New South Wales, Australia. Scale bars: 0.1 mm.

FIGURE 16. Thrombasia evalina sp. nov. paratype, male, 10.2 mm, AM P.69060, from east of Broken Bay, New South Wales, Australia. Scale bars: 0.1 mm.