Elasmopus norfolkensis Hughes, 2015, sp. nov.

Elasmopus norfolkensis sp. nov.

(Figs 13–15)

Type material. Holotype male, 4 mm, dissected, 4 slides, AM P.81484, Duncombe Bay, Norfolk Island, 29°03'30"S, 167°57'13"E, 15 m, algae, sponge and bryozoans, 13 May 2008, coll. J.K. Lowry, MI NFK 15°.

Paratypes: 1 female, 4.8 mm, dissected, 3 slides, AM P.92244, Cathedral Rock, Norfolk Island, 2900'13"S, 167°56'57"E, 10.5 m, overhang wall sponges and ascidians, 13 May 2008, coll. R.T. Springthorpe, MI NFK 6; 13 specimens, AM P.81490, Cathedral Rock, Norfolk Island, 29°00'13"S, 167°56'57"E, 10.5 m, overhang wall sponges and ascidians, 13 May 2008, coll. R.T. Springthorpe, MI NFK 6; 2 specimens, AM P.81491,Cathedral Rock, Norfolk Island, 29°12"S, 167°56'57"E, 10.5 m, overhang wall sponges and ascidians, 13 May 2008, coll. R.T. Springthorpe, MI NFK 6; 1 specimen, AM P.81487, Gun Club Reef, near Anson Point, Norfolk Island, 29°25"S, 167°54'44"E, 25 m, tufted brown and green algae, 17 May 2008, coll. J.K. Lowry, MI NFK 59; 1 specimen, AM P.81485, Puppies Point, Norfolk Island, 29°1'22"S, 167°55'8"E, 13 m, red algae, 17 May 2008, coll. R.T. Springthorpe, MI NFK 53; 1 specimen, AM P.81493, Fig Valley reef, Norfolk Island, 29°3'20"S, 167°55'44"E, 19.6 m, from bommie wall cored in sparse, 19 May 2008, coll. R.T. Springthorpe, MI NFK 66; 1 specimen, AM P.81486, dive site, ‘The Wall’, Nepean Island, near Norfolk Island, 29°4'17"S, 167°57'40"E, 9.6 m, red coralline algae cf Amphiroa anceps, 15 May 2008, coll. L.E. Hughes, MI NFK 49; 2 specimens, AM P.81488, dive site ‘The Wall’, Nepean Island, near Norfolk Island, 29°4'17"S, 167°57'40"E, 17 m, green algae Halimeda sp., 15 May 2008, coll. J.K. Lowry, MI NFK 45; 1 specimen, AM P.81494, dive site ‘The Wall’, Nepean Island, near Norfolk Island, 29°4'17"S, 167°57'40"E, 17 m, green algae Halimeda sp., 15 May 2008, coll. J.K. Lowry MI NFK 45; 1 male, AM P.81497, Swiss Cheese Reef, Norfolk Island 29°00'23"S, 167°56'50"E, 12 m, vertical face encrusted with sponges, under overhang, 15 May 2008, coll. R.T. Springthorpe, MI NFK 37; 1 male, AM P.81489, Swiss Cheese Reef, Norfolk Island, 29°00'23"S, 167°56'50"E, 14 m, overhang, sponges, encrusting algae, 15 May 2008, coll. J.K. Lowry MI NFK 38; 1 male, AM P.81492, Duncombe Bay, Norfolk Island, 29°03'30"S, 167°57'13"E, 15 m, green algae Caulerpa racemosa, 13 May 2008, coll. J.K. Lowry, MI NFK 17.

Type locality. Duncombe Bay, Norfolk Island, South Pacific, 29°03'30"S, 167°57'13"E.

Etymology. Named for the type locality, Norfolk Island.

Description. Of holotype male, 4 mm, AM P.81484.

Head. Eyes ovate; lateral cephalic lobe broad, apically rounded, anteroventral margin with notch/slit, corner rounded. Antenna 1 longer than antenna 2; peduncular article 1 subequal in length to article 2, with 2 robust setae on posterodistal margin; peduncular article 2 longer than article 3; flagellum articles as long as broad; with 16 articles; accessory flagellum short, 3-articulate. Antenna 2 peduncular article 2 cone gland extending beyond peduncular article 3; peduncular article 4 longer than article 5; flagellum with 7 articles. Mandible molar welldeveloped triturative, incisor cuspidate; accessory setal row, with 4 setae; palp 3-articulate; well-developed, article 3 weakly falcate, long, length 6 width. Lower lip inner lobes present, outer lobes ducts without ducts, mandibular lobes straight apically rounded. Maxilla 1 inner plate subquadrate, with 2 apical plumose setae. Maxilliped palp propodus with small distomedial flap.

Pereon. Gnathopod 1 coxa anterior margin concave, anteroventral corner slightly produced, acute; merus without posterodistal tooth; carpus twice as long as broad, longer than propodus, length 1.1 propodus, anterior margin with a few slender setae; propodus anterior margin with a few rows of slender setae, medial surface setal comb absent, palm subacute, straight, entire, defined by posterodistal corner with 4 robust setae. Gnathopod 2 subchelate; coxa posteroventral corner notch absent; basis slender, anterodistal corner subquadrate; merus with rounded distoventral corner; carpus compressed, lobate, projecting between merus and propodus, length 0.9 breadth; propodus expanded, palm acute, smooth, convex, with slender medial setal bunch, palm length 0.8 propodus posterior margin, subquadrate distomedial shelf with group of 10 robust setae, subpalmar surface smooth, palm defining by subpalmar socket with 1 robust seta; dactylus posterior margin with proximal tooth, apically subacute, reaching end of palm and closing into subpalmar socket. Pereopods 5–7 basis expanded, posterior margin without long slender setae; merus and carpus not broadened; dactylar ungues simple. Pereopod 5 basis posterior margin straight, weakly serrate, posteroventral corner broadly rounded. Pereopod 6 basis posterior margin serrate, tapering distally, posteroventral corner narrowly rounded to subquadrate. Pereopod 7 basis posterior margin convex, serrate, posteroventral corner narrowly rounded to subquadrate.

Pleon. Epimera 1–3 posteroventral corner with small acute tooth, ventral margin smooth. Urosomite 1 without carina. Uropod 1 peduncle with 1 basofacial seta; inner ramus longer than outer ramus, 0.8 peduncle length. Uropod 2 inner ramus longer than outer ramus, subequal in length to peduncle. Uropod 3 inner ramus short, length 1.9 breadth, subequal in length to outer ramus, longer than peduncle; rami distally truncated, apical robust setae short. Telson (based on female paratype) deeply cleft (80%), lobes broader than long, abutting, apically rounded with 1 pair of subapical robust setae.

Female (sexually dimorphic characters). Of paratype female, 4.8 mm, AM P.92244. Gnathopod 2 propodus palm subacute, straight, margin weakly irregular, lined with a few robust setae and defined by 3 loosely clustered robust setae; dactylus reaching end of and closing along palm.

Remarks. The male gnathopod 2 with greatly elongate dactylus more than three quarters the length of the propodus, is similar to Elasmopus aduncus Myers, 1995; E. gracilis Schellenberg, 1938; E. piikoi Barnard, 1970; E. temori Barnard, 1979 and E. spinidactylus Chevreux, 1908. The serrate posterior margin of the pereopod 7 basis separates E. norfolkensis sp. nov. from these species. Other distinctive features of E. norfolkensis sp. nov. include the gnathopod 2 dactylar socket on the proximal mid facial surface of the dactylus and the proximal tooth on dactylus posterior margin.

Elasmopus norfolkensis sp. nov. differs from E. gracilis Myers, 1986 in having the posterior margins of pereopods 5–7 basis straight and anterior margin lined in robust setae. Also gnathopod 1 in E. gracilis has the carpus anterior margin with long slender setae which is not apparent in E. norfolkensis sp. nov.

Distribution. South Pacific Ocean:Tasman Sea: Norfolk Island (current study).