Heteroptychus apophysis Baba 2018, n. sp.

Heteroptychus apophysis n. sp.

Figures 289-291

TYPE MATERIAL — Holotype: Solomon Islands. SALOMON 2 Stn CP 2269, 7°45.1’S, 156°56.3’E, 768-890 m, 4.XI.2004, 1 ♂ 5.1 mm, (MNHN-IU-2014-17104). Paratype: Solomon Islands. SALOMON 2 Stn DW2238, 06°53’S, 156°21’E, 470- 443 m, 30.X.2004, 1 ♂ 5.1 mm (MNHN-IU-2014-10139).

ETYMOLOGY„ The specific name is a noun in apposition from the Greek apophysis (process, projection) for two projections on the branchial lateral margin, by which the species is distinguished from U. paulae n. sp. (see below).

DISTRIBUTION„ Solomon Islands, 632- 890 m.

DESCRIPTION„ Medium-sized species. Carapace: 0.8 × as long as broad, greatest breadth 1.9 × distance between anterolateral spines. Dorsal surface polished, moderately convex from anterior to posterior, ridged along posterior twofifths of lateral margin. Lateral margin strongly convex around posterior third, with rounded process on anterior end of branchial margin, followed by smaller one at anterior end of posterior branchial margin; anterolateral spine prominent, horizontally directed straight forward reaching apex of rostrum. Rostrum broad triangular, with interior angle of 36- 40°, straight horizontal, reaching tip of eye; length 0.7 × breadth, 0.25-0.28 × that of remaining carapace; dorsal surface flattish. Lateral limit of orbit without spine. Pterygostomian flap anteriorly produced to sharp spine; anterior surface well inflated, convex from dorsal to ventral, with 3 or 4 blunt processes of good size; posterior height 0.2 × anterior height.

Sternum: Excavated sternum with bluntly subtriangular anterior margin, surface with sharp ridge in midline on anterior half. Sternal plastron 0.6 × as long as broad, lateral extremities convexly divergent posteriorly, sternite 6 broadest. Sternite 3 anterior margin excavated in broad V-shape with median notch lacking flanking spine. Sternite 4 with convex anterolateral margin.

Abdomen: Smooth and polished. Somite 1 in profile gently convex from anterior to posterior. Somite 2 2.8-3.0 × broader than long; pleural lateral margin slightly concave, strongly divergent posteriorly, ending in blunt tip. Pleura of somites 3-4 ending in rounded margin. Telson 0.4 × as long as broad; posterior plate feebly concave on posterior margin, length 1.3 × that of anterior plate.

Eyes: 1.6 × as long as broad, subovate. Cornea 0.6 × length of remaining eyestalk.

Antennule and antenna: Ultimate article of antennular peduncle 3.2-3.8 × longer than high. Antennal peduncle relatively short and slender. Article 2 without lateral spine. Antennal scale ending in proximal third or midlength of article 4, distinctly articulated. Distal 2 articles unarmed; article 5 1.2-1.4 × longer than article 4, breadth 0.4-0.5 × height of ultimate antennular article. Flagellum of 11 segments directed posterolaterally.

Mxp: Mxp1 with bases broadly separated. Mxp3 basis with 2 obsolescent denticles or unarmed on mesial ridge. Ischium relatively short, 0.4 × as long as merus, crista dentata with 2-4 denticles on proximal half, flexor margin not rounded distally. Merus relatively thick mesio-laterally, with rounded ridge along flexor margin, unarmed. No spine on carpus.

P1: Smooth and nearly glabrous except for fingers, 7.2-7.8 × longer than carapace. Ischium with basally broad, distally blunt distodorsal process and lobe-like proximal process overhanging basis. Merus with 3 spines on distal margin (1 small median, 2 large mesial) and 1 or 2 small mesial marginal protuberances proximal to distal end, length 1.7-1.9 × that of carapace. Carpus 1.5-1.7 × longer than merus, with 4 terminal spines and 2 rows of short blunt spines along mesial margin. Palm 4.0- 4.8 × longer than broad, 0.5-0.6 × broader than high, 0.7-0.8 × as long as carpus, mesial and lateral margins subparallel, mesial margin sharply ridged, with 9 or 10 short spines. Fingers half as long as palm, gaping in proximal two-thirds, straightly fitting to each other in distal half when closed, relatively slender, distally spooned; opposable margin of movable finger with prominent truncate process at midlength of gaping portion or distal to position of somewhat shorter truncate process on fixed finger.

P2-4: Meri subequal on P2 and P3, P4 merus 0.5 × length of P3 merus; length-breadth ratio, 6.3-6.7 on P2, 6.2-6.5 on P3, 3.6-3.7 on P4; P2 merus 0.9-1.0 × length of carapace,1.4 × length of P2 propodus, P3 merus 1.3-1.4 × length of P3 propodus, P4 merus 0.7-0.8 × length of P4 propodus. Carpi subequal in length on P2 and P3, P4 carpus one-third length of P3 carpus; slightly (1.1 x) longer than propodus on P2 and P3, much shorter (0.4 x) on P4; carpus-dactylus length ratio, 1.5-1.7 on P2 and P3, 0.6-0.7 on P4. Propodi subequal on P2 and P3, P4 propodus 0.9 × length of P3 propodus; propodusdactylus length ratio, 1.6 on P2, 1.4-1.7 on P3 and P4; flexor margin concavely curving in lateral view, unarmed. Dactyli subequal on P2 and P3, slightly shorter on P4 than on P2 and P3; dactylus-carpus length ratio, 0.6 on P2 and P3, 1.5-1.7 on P4; flexor margin with row of 12-14 slender, proximally diminishing spines, ultimate and penultimate spines subequal.

REMARKS„ This species strongly resembles U. paulae n. sp. in nearly all aspects. Their relationships are discussed under that species (see below).