Uroptychus norfolkanus, 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 : 356-359

Uroptychus norfolkanus n. sp.

Figures 174 , 175

TYPE MATERIAL — Holotype: New Caledonia, Norfolk Ridge. BERYX 11 Stn DW 38, 23°37.53’S, 167°39.42’E, 550-690 m, 19.X.1992, ov. ♀ 4.8 mm ( MNHN-IU-2012-681 ).

ETYMOLOGY„ Named for the type locality of the species.

DESCRIPTION„ Small species. Carapace: 1.4 × broader than long (0.7 × as long as broad), broadest on posterior third; greatest breadth 2.1 × distance between anterolateral spines. Dorsal surface convex smoothly from anterior to posterior and from side to side, without depression bordering gastric and cardiac regions, sparsely covered with small pits suggesting to support short fine setae. Lateral margins convex on posterior third, finely granulose, and weakly ridged along posterior third; anterolateral spine short, distinctly larger than lateral orbital spine, directed forward. Rostrum directed somewhat ventrally, narrow triangular, with interior angle of 22°, distally proportionately broad; dorsal surface somewhat concave; lateral margin more or less convex, with 3 obsolescent spinules distally; length half that of remaining carapace, breadth one-third that of carapace measured along posterior margin. Lateral orbital angle with small, distinct spine separated from anterolateral spine by more than basal breadth of latter spine, and located at level of that spine. Pterygostomian flap smooth on surface, anterior margin angular, produced to distinct spine.

Sternum: Excavated sternum with convex anterior margin; surface with weak low ridge in midline. Sternal plastron 0.7 × as long as broad, broadest on sternite 7; lateral extremities convexly divergent posteriorly. Sternite 3 shallowly depressed; anterior margin broadly excavated in subsemicircular shape with 2 obsolescent submedian spines separated by small shallow concavity, laterally blunt angular. Sternite 4 with anterolateral margin convex and denticulate, anteriorly roundish, posterior margin half as long as anterolateral margin. Anterolateral margin of sternite 5 anteriorly feebly angular, 1.5 × longer than posterolateral margin of sternite 4.

Abdomen: Somite 1 moderately convex from anterior to posterior, without transverse ridge. Somite 2 tergite 3.0 × broader than long; pleural lateral margin concavely divergent posteriorly, posterolaterally blunt. Pleuron of somite 3 with blunt posterolateral terminus. Telson 0.4 × as long as broad; posterior plate equally long as anterior plate, concave on posterior margin.

Eye: 1.7 × longer than broad, barely reaching midlength of rostrum, mesial and lateral margins subparallel. Cornea not inflated, length more than half length of remaining eyestalk.

Antennule and antenna: Ultimate article of antennule 2.9 × longer than high. Antennal peduncle overreaching cornea, slightly overreaching midlength of rostrum. Article 2 with small lateral spine. Antennal scale tapering distally, 2.2 × broader than article 5, extending far beyond eye and slightly beyond proximal second segment of flagellum. Articles 4 and 5 each with small distomesial spine, article 5 1.4 × longer than article 4, breadth two-thirds height of antennular ultimate article. Flagellum of 9 segments slightly overreaching rostral tip, far falling short of distal margin of P1 merus.

Mxp: Mxp1 with bases broadly separated. Mxp3 with fine plumose setae other than brushes on distal articles. Basis having mesial ridge lobe-like and nearly smooth. Ischium with flexor margin not rounded distally; crista dentata with denticles obsolescent on proximal half, very tiny on distal half. Merus 2.1 × longer than ischium; with small distolateral spine; flexor margin roundly ridged, with 6 tubercle-like processes on distal third. Carpus with small distolateral spine.

P1: 4.3 × longer than carapace, sparingly covered with short fine plumose setae. Ischium with small dorsal spine, ventromesial margin with row of small spines, with no distinct subterminal spine. Merus with small distomesial and distolateral spines on ventral surface, row of denticles along distodorsal margin, and a few small spines on proximal mesial margin; length 0.9 × that of carapace. Carpus subcylindrical, 1.3 × longer than merus, distodorsal margin with row of denticles. Palm 2.7 × longer than broad, 1.3 × longer than carpus. Fingers moderately depressed and relatively broad, distally incurved, crossing when closed, not gaping; fixed finger with low eminence at midlength of opposable margin; movable finger 0.5 × as long as palm, opposable margin with denticulate eminence (higher than opposite eminence on fixed finger) proximal to midlength. P2-4: P2 and P4 missing, right P3 broken, only left P3 available. P3 relatively thick mesio-laterally, with fine soft setae. Merus 3.4 × broader than long, about as long as propodus; dorsal margin rounded, not cristate, with 2 small denticle-like spines proximally; ventrolateral margin distally ending in small spine. Carpus 1.3 × longer than dactylus; dorsal margin with tiny proximal spine. Propodus 2.0 × longer than carpus; flexor margin strongly convex on distal third, with pair of terminal spines preceded by 7 spines, 6 of these situated on convex margin, last somewhat more proximal in position. Dactylus 0.8 × length of carpus, 0.4 × length of propodus; tapering distally and well curved; flexor margin with 7 triangular spines proximally diminishing, more or less close to one another and somewhat inclined but proximal spines nearly perpendicular to margin.

Eggs. Number of eggs carried, 15; size, 0.79 × 1.00 - 0.79 × 1.04 mm.

REMARKS — The new species resembles U. edisonicus Baba & Williams, 1998 , U. latior n. sp. and U. pedanomastigus n. sp. in the carapace shape, in having a deeply excavated, semicircular anterior margin of sternite 3, in having the distally broadened P2-4 propodi, in the arrangement of flexor marginal spines of P2-4 dactyli, and in having nearly spineless P1 with fingers distally strongly incurved. Uroptychus norfolkanus is distinguished from U. edisonicus ( Figure 121 ) by the antenna that has articles 4 and 5 each with a distomesial spine instead of being unarmed, and the antennal scale reaching the proximal third segment of the antennal flagellum instead of terminating in the distal end of article 5; the P3 propodus has an additional spine remotely proximal to the distal group of flexor marginal spines, which spine is absent in U. edisonicus (P2 and P4 missing in U. norfolkanus ); and the P3 dactylus is shorter than instead of subequal to the P3 carpus (0.8 versus 1.0). Uroptychus norfolkanus differs from U. latior in having the anterolateral spine directed straight forward instead of anteromesially, in having the pterygostomian flap anteriorly produced to a distinct spine instead of bearing a tiny spine, in having the P3 propodi with an additional spine remotely proximal to the distal group of flexor marginal spines, in having the eyes subcylindrical instead of distally narrowed, and in having the anterior margin of sternite 3 with obsolescent submedian spines, not smoothly semicircular. The relationships between U. norfolkanus and U. pedanomastigus are discussed under the account of the latter species (see below).

Figures

FIGURE 121 Uroptychus edisonicus Baba& Williams,1998,holotype,ovigerous female 4.6 mm,USNM 251479.A, anterior part of carapace,dorsal.B, anterior part of sternal plastron,excavated sternum and basal parts of Mxp1 included.C, left Mxp3,crista dentata,ventral.D, right P2,setae omitted,lateral.E, same, distal part, setae omitted.F, right P3,lateral.G, same, distal part, lateral.H, right P4,lateral.Scale bars:A,B, D-H,1 mm; C,0.5 mm.

FIGURE 174 Uroptychus norfolkanus n. sp.,holotype,ovigerous female 4.8 mm (MNHN-IU-2012-681).A, carapace and anterior part of abdomen, proximal part of left P1 included,dorsal.B, same,lateral.C, sternal plastron,with excavated sternum and basal parts of Mxp1.D,anterior part of sternal plastron. E, telson.F, left antenna,ventral.G, right Mxp3, ventral.H, same, setae omitted, lateral.Scale bars:1 mm.

FIGURE 175 Uroptychus norfolkanus n. sp., holotype, ovigerous female 4.8 mm (MNHN-IU-2012-681). A, left P1, proximal part, setae omitted, ventral. B, same, proximal part omitted, dorsal.C, same, fingers,ventral. D, left P3, lateral. E, same, distal part, setae omitted,lateral.Scale bars:1 mm.