Uroptychus bellus Faxon, 1893

Baba, Keiji & Wicksten, Mary K., 2019, Chirostyloidean squat lobsters (Crustacea: Decapoda: Anomura) from the Galapagos Islands, Zootaxa 4564 (2), pp. 391-421 : 403-408

Uroptychus bellus Faxon, 1893

( Figs. 9–11 , 17C )

Uroptychus bellus Faxon, 1893: 193 (type locality: SW Point of Azuero Peninsula, Panama, 333–589 m).— Faxon 1895: 102, p. 26, figs 2, 2a, 2b.— Baba 2005: 224 (synonymies, key).

Type material. USNM 29166 , lectotype, ovigerous female (CL 5.5 mm), Albatross Sta. 3354, 7°09'45"N, 80°50'00"W, 322 fms [589 m], 23 February 1891 [examined] . MCZ IZ CRU-4567 , paralectotype, male, Albatross Sta. 3355, 7°12'20"N, 80°55'00"W, 182 fms [333 m], 23 February 1891 [not examined] .

Other material examined. CDF NA064-130-01-01-A, 1 male (CL 4.5 mm), ROV Dive H1443, 0°22.8348'N, 90°49.6748'W (between Santiago and Isabela Islands), 474 m, with black coral ( Antipatharia ), 6 July 2015.

Description. Carapace: Broader than long (0.9 × as long as broad); greatest breadth measured at posterior third, 1.8 × distance between anterolateral spines. Dorsal surface smooth, glabrous and unarmed except for very small spine (barely discernible in lectotype) slightly dorsomesial to anterior end of branchial margin, weakly convex from anterior to posterior, without depression between gastric and cardiac regions. Lateral margins convexly divergent posteriorly; with row of small spines, with no ridge along posterior portion; anterolateral (first) spine well developed, horizontal and directed straight forward, situated slightly posterior to position of lateral orbital spine at base but nearly reaching to [slightly overreaching] its tip; second lateral spine remote from anterolateral spine, situated at anterior end of branchial margin, followed by 6 (left) or 8 (right) [9 or 10] posteriorly diminishing small spines, last spine situated at posterior quarter of length. Rostrum long triangular, [1.6]–1.8 × as long as broad, with interior angle of 20°; horizontal and directed straight forward; length [0.6]–0.7 × postorbital carapace length, breadth [0.5]–0.6 × that of carapace measured at posterior margin; lateral margins nearly straight and spineless; dorsal surface concave. Lateral orbital spine slightly smaller than anterolateral spine. Pterygostomian flap anteriorly more or less roundish, bearing very small anterior spine, surface with very small spines on anterior portion, obsolescent spines on posterior portion.

Thoracic sternum: Excavated sternum anteriorly sharp triangular, with sharp ridge in midline. Sternal plastron 0.8 × as long as broad, transverse ridges obsolete; sternites 4–7 successively broader posteriorly but sternite 7 slightly broader than sternite 6. Sternite 3 moderately depressed, anterolaterally produced, lateral end with small spine on each side; anterior margin deeply excavated but medially produced, subtriangular. Sternite 4 anterolateral margin slightly convex, irregular on anterior half bearing obsolescent crenulations, length 1.8 × that of posterolateral margin. Anterolateral margins of sternite 5 convexly divergent posteriorly, 1.2–1.3 × longer than posterolateral margin of sternite 4.

Abdomen: Tergites smooth and glabrous. Somite 1 tergite dorsally convex from anterior to posterior, without transverse ridge. Somite 2 tergite 3.0 × broader than long; pleuron anterolaterally angular, posterolaterally sharply tapering, lateral margins concavely divergent posteriorly. Pleuron laterally angular on somite 3, blunt on somite 4, rounded on somite 5. Telson 0.4 × as long as broad; posterior plate moderately concave on posterior margin, length 1.5 × that of, breadth 0.8 × that of anterior plate.

Eye: Globular (about as long as broad), ending at proximal third of rostrum. Cornea not dilated, about as long as remaining eyestalk.

Antennule and antenna: Ultimate article of antennular peduncle 4.4 × longer than high. Antennal peduncle well overreaching cornea, slightly overreaching midlength of rostrum. Article 2 with acute lateral spine. Antennal scale 1.6–[2.0] × broader than article 5, terminating in or [slightly overreaching] distal quarter of article 5. Article 4 with small distomesial spine. Article 5 1.6–[1.8] × longer than article 4, breadth 0.6 × height of ultimate antennular article; with strong distomesial spine. Flagellum of 10 segments slightly overreaching rostral tip, falling short of distal end of P1 merus.

Mxp: Mxps 1 with bases separated between triangular anterior end of excavated sternum. Mxp 3 moderately setose; basis with obsolescent distal denticle on mesial ridge; ischium with 10 or 11 denticles on crista dentata, flexor margin somewhat rounded distally; merus 2.3 × longer than ischium, relatively thick mesio-laterally, ridged along flexor margin, with 1 distolateral and 2 flexor marginal spines, proximal flexor spine slightly distal to midlength; carpus with 1 distolateral and 2 extensor spines, all smaller than distolateral spine of merus.

P1: Sparsely setose; length 4.8 × carapace length. Ischium dorsally with relatively short sharp distal spine and small proximal spine, ventromesially with well-developed subterminal spine. Merus subcylindrical, proximally moderately narrowed, with 5 rows of spines continued onto carpus: 2 dorsal (lateral of these rows of small spines), 1 mesiodorsal, 1 mesioventral, 1 ventral; and 1 strong distolateral spine proximally accompanying small spine; length 1.1 × carapace length. Carpus not depressed, slightly higher than broad, 1.1 × longer than merus, distoventral (mesial and lateral) spines strong. Palm proximally narrowed, 3.5 × longer than broad, 1.1 × longer than carpus; 0.8 × as high as broad; row of 7 small spines along mesial margin, and row of 5 or 6 tiny spines mesial to midline on dorsal surface. Fingers directed slightly laterally, gaping in proximal two-thirds, crossing in distal third when closed, each ending in sharp incurved spine; movable finger slightly less than half as long as palm; opposable margin of movable finger with strong blunt proximal process, that of fixed finger bluntly denticulate, with low prominence at distal third.

P2–4: Meri relatively thick mesio-laterally, successively shorter posteriorly (P3 merus 0.96 × length of P2 merus, P4 merus 0.8 × length of P3 merus), breadths subequal on P2–4; length-breadth ratio, [4.6]–5.1 on P2, 4.6 on P3, 3.8 on P4; dorsal margin with 4 small to [8 moderately-sized] spines on P2, 3 spines on P3, none on P4, distally unarmed; ventrolateral margin with well-developed distal spine followed by small one. P2 merus 0.8 × carapace length, 1.4 × length of P2 propodus; P3 merus 1.2 × length of P3 propodus; P4 merus 0.9 × length of P4 propodus. Carpi subequal on P2 and P3, shorter on P4 (P4 carpus 0.9 × length of P3 carpus); carpus-propodus length ratio, 0.8 on P2 and P3, 0.6 on P4; extensor margin with 7 or 8 spines on P2 and P3 (smaller on P3 than on P2), obsolescent spines on P4. Propodi successively longer posteriorly; flexor margins distinctly convex around distal third or [slightly distal to midlength], with pair of terminal spines preceded by [6]–8, 7, 6 movable spines on P2, P3, P4 respectively, proximalmost small. Dactyli curving at proximal third, length half that of propodus on P2– 4; dactylus-carpus length ratio, 0.6 on P2 and P3, 0.7 on P4; flexor margin with slender ultimate spine preceded by 5 sharp triangular spines, distal second and third (penultimate and antepenultimate) subequal in breadth, fourth and fifth broader than second and third, last (proximalmost) short.

Color: Overall pale yellowish orange.

Host: Taken with a black coral ( Antipatharia ).

Remarks. Uroptychus bellus was originally described based on two syntypes. One of these from Albatross Station 3354, an ovigerous female, USNM 29166, is designated here as a lectotype, and the other syntype, a male, MCZ CRU 4567, from Albatross Station 3355, as a paralectotype. The present material agrees well in major features with the lectotype examined. Because of the brevity of the available descriptions of the species, a full description, based largely on the R/V Nautilus specimen, is provided.

The unusual shape of sternite 3 displayed by this species, namely the excavated anterior margin medially produced triangularly, is shared by two western Atlantic species, Uroptychus marissae Baba & Wicksten, 2015 and U. minutus Benedict, 1902 , but not by any Indo-Pacific species ( Baba & Wicksten 2015). These western Atlantic species have flexor spines (except for the slender ultimate spine) of the P2–4 dactyli successively diminishing proximally, the eyes are elongate, and the P2–4 propodi have no inflation on the distal flexor margin, characters that are different from U. bellus .

Of 222 Indo-West Pacific species known to date (Baba, 2018), Uroptychus lanatus Baba, 2018 , from Indonesia and Vanuatu, is the closest to this new species. Shared characters include the carapace dorsally unarmed and laterally spinose, the P2–4 propodi distally ending in a pair of spines preceded by a row of movable unpaired spines, the P2–4 dactyli with the ultimate (distal first) spine more slender than the penultimate (distal second), and the penultimate and antepenultimate (distal third and fourth) subequal. In addition to the difference in the shape of sternite 3, the following characters separate U. bellus from U. lanatus : the eye is globular rather than elongate; the antennal scale falls short of instead of extending far beyond the distal end of the antennal article 5; antennal article 5 bears a much stronger distomesial spine; the lateral orbital spine is of good size, only slightly smaller instead of much smaller than the anterolateral spine of the carapace; the pleuron of abdominal somite 2 is posterolaterally tapering instead of having a blunt terminus; P1 is spinose instead of nearly spineless; the P2–3 meri and carpi are spinose rather than smooth and unarmed on the dorsal or extensor margins; and flexor spines of the P2–4 dactyli are successively broadened (the distal fourth and fifth spines in particular) instead of diminishing toward the proximal end.

Among the six eastern Pacific species, including U. compressus n. sp. (see below), U. bellus is readily distinguished from the other species by the shape of sternite 3, as well as the P2–4 propodi, which bear a strongly convex flexor margin around the distal one-third.

Distribution. Off Mariato Point, Panama, at depth of 333–589 m, and now between Santiago and Isabela Islands, Galapagos Islands, at 474 m depth.

Figures

FIGURE 9. Uroptychus bellus Faxon, 1893, male (CL 4.5 mm), CDF NA064-130-01-01-A. A, carapace and anterior part of abdomen, dorsal. B, same, lateral. C, sternal plastron, with excavated sternum and basal parts of Mxp1. D, pleura of abdominal somites 2–5, dorsolateral. E, telson. F, left antenna, ventral. G, left Mxp3, ventral. H, same, lateral. Scales = 1 mm.

FIGURE 10. Uroptychus bellus Faxon, 1893, male (CL 4.5 mm), CDF NA064-130-01-01-A. A, left P1, dorsal. B, same, mesial. C, same, palm and fingers omitted, ventral. D, right P2, lateral. E, same, distal part, setae omitted. F, right P3, lateral. G, same, distal part. H, right P4, lateral. I, same, distal part. Scales = 1 mm.

FIGURE 11. Uroptychus bellus Faxon, 1893, lectotype, ovigerous female (CL 5.5 mm), USNM 29166. A, carapace, dorsal. B, same, lateral. C, anterior part of sternal plastron, with excavated sternum and basal parts of Mxp1. D, left antenna, ventral. E, right Mxp3, merus and carpus, lateral. F, right P2, lateral. G, same, distal part. Scales = 1 mm.

FIGURE 17. A, Eumunida subsolanus n. sp., holotype, female (CL 6.0 mm), CDF NA064-018-01-03-A. B, Heteroptychus nautilus n. sp., holotype, ovigerous female (CL 5.2 mm), CDF NA064-009-01-01-A. C, Uroptychus bellus Faxon, 1893, male (CL 4.5 mm), with Antipatharia, CDF NA064-130-01-01-A. D, Uroptychus occidentalis Faxon, 1893, two specimens on Chrysogorgia sp., CDF NA064-013-01-01-A. E, same, right ovigerous female (CL 11.4 mm), left specimen not available for study, CDF NA064-013-01-01-A.