Heteroptychus lemaitrei, Baba, 2018

Baba, Keiji, 2018, Chirostylidae of the Western and Central Pacific: Uroptychus and a new genus (Crustacea: Decapoda: Anomura), Tropical Deep-Sea Benthos (Mémoires du Muséum national d'Histoire naturelle 212), pp. 1-612 : 590-593

Heteroptychus lemaitrei n. sp.

Figures 298 , 299

Uroptychus scambus — Baba 2005: 58 (not H.scambus ( Benedict, 1902)) .

TYPE MATERIA L — Holotype: New Caledonia, Norfolk Ridge. BIOCAL Stn CP27, 23°07’S, 166°26’E, 1850-1900 m, 28- 29.VIII.1985, ♂ 5.4 mm ( MNHN-IU-2013-12289 ) . Paratypes: Wallis and Futuna Islands. MUSORSTOM 7 Stn CP623, 12°34’S, 178°15’W, 1280-1300 m, 28.V.1992, 1 ♂ 6.2 mm (MNHN-IU-2014-17129) . Solomon Islands. SALOMON 1 Stn CP1761, 8°46.5’S, 160°01.6’E, 191-290 m, 27.IX.2001, 1 ♂ 5.3 mm (MNHN-IU-2014-17130).

ETYMOLOGY„ Named for Rafael Lemaitre of the Smithsonian Institution, for his help and friendship.

DISTRIBUTION„ Solomon Islands, Wallis and Futuna Islands, Norfolk Ridge and Makassar Strait; 1280-2084 m.

DESCRIPTION„ Medium-sized species. Carapace: 0.7-0.8 × as long as broad, greatest breadth 1.9-2.1 × distance between anterolateral spines. Dorsal surface polished, moderately convex from anterior to posterior, ridged along posterior half of lateral margin. Lateral margins convexly divergent posteriorly but feebly concave at anterior third, with small protuberance at anterior end of branchial margin; greatest breadth of carapace measured around posterior third of length; anterolateral spine prominent, horizontally directed more or less anteromesially, ending in or somewhat overreaching midlength of rostrum. Rostrum distally narrow triangular, with interior angle of 15-17°, straight, directed moderately dorsally, overreaching eyes by one-quarter length of rostrum; length subequal to breadth, 0.35 length of remaining carapace; dorsal surface flattish. Lateral limit of orbit acuminate or with small spine. Pterygostomian flap anteriorly produced to sharp strong spine; anterior surface well inflated, with no longitudinal ridge in midline; posterior height 0.3 × anterior height.

Sternum: Excavated sternum with triangular anterior margin, surface with sharp ridge in midline on anterior half. Sternal plastron 0.63-0.65 as long as broad; lateral extremities of sternites 4-7 slightly convex, sternite 6 broadest. Sternite 3 having anterior margin broadly and deeply excavated, medially slightly or somewhat produced with pair of short blunt processes.

Abdomen: Smooth and polished. Somite 1 gently convex from anterior to posterior. Somite 2 tergite 2.5-2.7 × 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 1.3-1.4 × that of anterior plate.

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

Antennule and antenna: Ultimate article of antennular peduncle 2.6-3.3 × longer than high. Antennal scale fused with article 2, as broad as or slightly broader than article 5, ending in or barely reaching midlength of article 4. Distal 2 articles unarmed; article 5 1.2-1.4 × as long as article 4, breadth 0.4 × height of ultimate antennular article. Flagellum of 11-13 segments.

Mxp: Mxp1 with bases broadly separated. Mxp3 basis with 1 denticle near distal end of mesial ridge. Ischium relatively short, 0.4 × as long as merus, crista dentata with 1 or 2 obsolescent denticle proximally, 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, 7.6-8.1 × longer than carapace. Ischium with well-developed distodorsal spine and short, distally blunt proximal process overhanging basis. Merus with 2 distal spines mesially (distodorsal strong, distoventral small), length 1.7-1.9 × that of carapace. Carpus 1.4-1.5 × longer than merus, dorsally with 3 or 4 terminal spines, ventromesially with 6-8 spines. Palm 3.4-3.6 × longer than broad, 0.5-0.6 × as broad as high, 0.8 × length of carpus; mesial margin sharply ridged and cristiform with obsolescent serration. Fingers directed anterolaterally, gaping in proximal half, straightly fitting to each other in distal half when closed, relatively slender, distally spooned; movable finger 0.5-0.6 × length of palm, opposable margin with prominent blunt process at midlength of gaping portion, distal to position of opposite truncate process on fixed finger.

P2-4: Sparsely setose on meri and carpi, thickly so along prehensile margins of propodi and dactyli. Meri subequal on P2 and P3, P4 merus 0.5-0.6 × length of P3 merus; length-breadth ratio, 5.1-5.6 on P2, 5.2-6.2 on P3, 3.5-3.9 on P4; P2 merus 0.9-1.1 × length of carapace, 1.2 × length of P2 propodus, P3 merus 1.2-1.3 × length of P3 propodus, P4 merus 0.8 × length of P4 propodus. Carpi subequal in length on P2 and P3, P4 carpus 0.4-0.5 × length of P3 carpus; carpusdactylus length ratio, 1.4 on P2, 1.4-1.5 on P3, 0.6-0.7 on P4. Propodi subequal on P2 and P3, P4 propodus 0.9 × length of P3 propodus; propodus-dactylus length ratio, 1.5 on P2, 1.5-1.6 on P3, 1.4 on P4; flexor margins concavely curving in lateral view, unarmed. Dactyli subequal on P2-4, dactylus-carpus length ratio, 0.7 on P2 and P3, 1.5-1.6 on P4; flexor margins with row of 14 or 15 sharp spines proximally diminishing and slightly inclined or subperpendicular to margin, ultimate spine subequal to or somewhat longer than penultimate spine.

REMARKS — The fusion of the antennal scale with article 2 is shared by H. claudeae n. sp., H. lemaitrei n. sp. and the western Atlantic H. brevis ( Benedict, 1902) (see above under H. claudeae ). Heteroptychus lemaitrei differs from H. claudeae in having a small but distinct protuberance at the anterior end of the carapace branchial margin and in having the rostrum distally spiniform rather than narrow triangular.

The material reported under Uroptychus scambus from the Makassar Strait ( Baba, 2005) was reexamined. The larger of the two male specimens can definitely be referred to H. lemaitrei , bearing a distinct protuberance, characteristic of this species, at the anterior branchal margin. In the smaller male, the protuberance is reduced to a very tiny denticle that is discernible only under high magnification; in addition, the P1 has less pronounced distal spines on the merus and carpus, with no distinct spines along the mesial margin of carpus. These differences appear to be size-related.

Figures

FIGURE 298 Heteroptychus lemaitrei n.sp.,holotype,male 5.4 mm (MNHN-IU-2013-12289).A, carapace and anterior part of abdomen,dorsal.B,same, lateral.C, pterygostomian flap,anterior part,dorsolateral.D, sternal plastron,with excavated sternum and basal parts of Mxp1. E, telson. F, right antennal peduncle, ventral.G, right Mxp3, ventral.Scale bars:1 mm.

FIGURE 299 Heteroptychuslemaitrei n.sp.,holotype,male 5.4 mm (MNHN-IU-2013-12289).A,left P1,dorsal.B, same,proximal part omitted,mesial.C,right P2, lateral.D, right P3,setae omitted, lateral. E, same, distal part, lateral.F, right P4, lateral.Scale bars:1 mm.