Uroptychus occidentalis Faxon, 1893

Baba, Keiji & Wicksten, Mary K., 2019, Chirostyloidean squat lobsters (Crustacea: Decapoda: Anomura) from the Galapagos Islands, Zootaxa 4564 (2), pp. 391-421 : 411-416

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Uroptychus occidentalis Faxon, 1893


Uroptychus occidentalis Faxon, 1893

( Figs. 14–16 View FIGURE 14 View FIGURE 15 View FIGURE 16 , 17D, E View FIGURE 17 )

Uroptychus nitidus occidentalis Faxon, 1893: 192 (type locality: Gulf of Panama, 838 m).— Faxon 1895: 101, pl. 26, figs. 1, 1a.

Uroptychus occidentalis .—Baba & Lin 2008: 18, fig. 10.

Type material. MCZ IZ 150981 View Materials , lectotype, male (CL 7.8 mm), Albatross Sta. 3384, off Panama [east of Punta Mala , Panama], 7°31'30"N, 79°14'0"W, 458 fms (838 m), 8 Mar. 1891 GoogleMaps . MCZ IZ CRU-4565 , paralectotypes, 2 ovigerous females (CL 9.3 mm, 10.3 mm), 1 female (CL 5.3 mm), collected with lectotype [examined] GoogleMaps .

Other material examined. CDF NA064-013-01-01-A, 1 ovigerous female (CL 11.4 mm), ROV Dive H1435, East Wolf Seamount, 1°13.3359'N, 91°06.0416'W, 873 m, with Chrysogorgia sp. ( Alcyonacea : Chrysogorgiidae ), 27 Jun. 2015.

Description. Carapace: 1.1 × longer than broad, greatest breadth measured at posterior third, 1.6–1.8 [1.7] × distance between anterolateral spines. Dorsal surface smooth, glabrous, moderately convex from anterior to posterior, with shallow depression between gastric and cardiac regions. Epigastric region with pair of short rows of granulations or obsolescent denticles. Lateral margins convexly divergent posteriorly; anterolateral spine of moderate-size, situated somewhat posterior to position of lateral orbital spine, varying from terminating at, to slightly overreaching, tip of smaller lateral orbital spine; branchial lateral margin with short oblique ridges or granulations on anterior third (obsolescent in smallest specimen), weakly ridged along posterior two-thirds. Rostrum 1.0–1.3 [1.1] × longer than broad, narrow triangular, with interior angle of 18–23 [22]°, [straight horizontal], slightly to distinctly curving dorsally (in larger ovigerous female paralectotype), lateral margins slightly concave, length 0.4–[0.5] × that of remaining carapace, breadth 0.5–[0.6] × that of carapace measured at posterior carapace margin; dorsal surface concave. Pterygostomian flap smooth on surface, anteriorly somewhat roundish, with very tiny spine directly ventral to rounded anterior terminus or at anterior terminus.

Thoracic sternum: Excavated sternum anteriorly sharp triangular; surface with rounded ridge in midline (with small spine in center in male lectotype). Sternal plastron slightly shorter than broad, sternites successively slightly broader posteriorly [sternites 4 and 5 subequally broad]. Sternite 3 well depressed; deeply excavated anterior margin with pair of well-developed submedian spines separated by sinus, anterolateral end rounded or bluntly angular, lateral extremity with small accompanying ventral spine. Sternite 4 anterolateral margin straight or slightly convex and irregular with distinct or obsolescent crenulations, produced to anterolaterally directed spine, length 1.7–2.0 [1.5] × that of posterolateral margin. Anterolateral margin of sternite 5 convexly divergent, slightly longer than posterolateral margin of sternite 4.

Abdomen: Smooth and glabrous. Somite 1 tergite moderately convex from anterior to posterior. Somite 2 tergite 2.3–[2.7] × broader than long; pleuron posterolaterally blunt, lateral margin gently concave and moderately divergent posteriorly. Pleuron of somite 3 laterally blunt, that of somite 4 laterally rounded. Telson 0.5–[0.6] × as long as broad; posterior plate weakly, moderately or [strongly] emarginate on posterior margin, length 1.4–[1.8] × that of, and breadth 0.7–0.9 [0.8] × that of, anterior plate.

Eye: 1.3–[1.6] × longer than broad, proximally somewhat narrowed, reaching distal quarter of rostrum, mesial and lateral margins slightly concave. Cornea somewhat dilated, about as long as remaining eyestalk.

Antennule and antenna: Ultimate article of antennule 2.3–3.4 [2.5] × longer than high (more slender in large specimens). Antennal peduncle overreaching cornea. Article 2 with short, distinct distolateral spine. Antennal scale varying from ending in midlength to distal quarter of article 5, breadth 1.3–1.7 [1.4] × that of article 5. Distal 2 articles unarmed. Article 5 1.6–2.0 [1.9] × length of article 4, breadth [0.4]–0.6 × height of ultimate antennular article. Flagellum of 14–21 [16 or 17] segments 1.4–[1.5] × length of rostrum, varying from barely reaching to slightly overreaching distal end of P1 merus.

Mxp: Mxps 1 with bases [adjacent] or somewhat or moderately separated. Mxp 3 barely setose on lateral surface. Basis with 3 or 4 denticles on mesial ridge. Ischium with [22]–25 denticles on crista dentata (smaller along distal two-thirds in smallest specimen); flexor margin not rounded distally. Merus [2.0]–2.2 × longer than ischium, ridged along unarmed flexor margin. Carpus with small proximal spine on extensor margin.

P1: 3.9 (male), 3.8–4.3 × (females; 5.3 × in larger ovigerous female paralectotype) carapace length; setose on fingers, sparsely so elsewhere. Ischium with 2 dorsal spines (distal one short and stout, proximal one small), ventromesially with several protuberances proximally, subterminal spine absent. Merus 0.9–[0.95] –1.3 × (in larger ovigerous female paralectotype) carapace length, bearing row of small spines along proximal mesial margin and another row of very small or obsolescent spines in midline (obsolete in smallest specimen), distolateral and distomesial spines small and blunt. Carpus 0.6 (in larger ovigerous female paralectotype)–0.8 × as high as broad, [1.1]–1.2 × longer than merus, ventral surface distally with several very small or obsolescent spines including very short blunt distomesial and distolateral spines (nearly smooth but distal two spines in small specimens). Palm 2.3– 3.5 (females), 2.1 (male) × longer than broad, 0.6 × (in larger ovigerous female paralectotype)–0.8 × as high as broad, 0.9–[1.0] × as long as carpus; roundly ridged along mesial margin, lateral and mesial margins subparallel or slightly convex, ventral surface convex from side to side with sparse tubercles on distal portion (smooth on male and smallest female), dorsal surface smooth. Fingers slightly gaping in proximal third in females, largely gaping in proximal three-fifths in male, opposable margin distal to gape nearly straight and minutely dentate, each finger distally ending in incurved short spine; movable finger half-length of palm, gaped margin with bicuspid process in females, obsolescently bicuspid strong process in male.

P2–4: Somewhat compressed mesio-laterally, with long setae on carpi and propodi, shorter setae on meri and dactyli (setae sparse in larger ovigerous female paralectotype). Meri successively shorter posteriorly (P3 merus 0.9 × length of P2 merus, P4 merus 0.7–[0.8] × length of P3 merus); length-breadth ratio, 4.0–4.8 [4.2] on P2, [3.5]–4.5 on P3, [3.3]–3.9 on P4 (in larger ovigerous female paralectotype), 6.5 on P2, 5.7 on P3, 5.1 on P4); dorsal margin unarmed, ventrolateral margin with obsolescent distal spine; P2 merus [0.7]–0.8 × (1.0 × in larger ovigerous female paralectotype) carapace length, [1.0]–1.2 × length of P2 propodus; P3 merus [1.0]–1.1 × length of P3 propodus; P4 merus [0.8]–0.9 × length of P4 propodus; Carpi successively shorter posteriorly; length 0.6 × that of propodus on P2, 0.5–0.6 × on P3, 0.5 × on P4. Propodi successively shorter posteriorly or [subequal on P2 and P3 and shorter on P4]; flexor margin ending in pair of spines preceded by 6 or 7 slender movable spines on distal half or distal twothirds on P2, [6]–8 spines on P3, [5] or 6 spines on P4. Dactyli proportionately broad distally, curved at proximal quarter, length 0.6–[0.7] × that of carpus on P2, [0.7]– 0.8 × on P3 and P4, 0.4 × length of propodus on P2–4; flexor margin with 10–13 moderately obliquely directed, triangular spines, ultimate slightly narrower than or subequal to penultimate.

Color: Overall pale orange, eggs reddish orange.

Eggs: Number of eggs carried, R/V Nautilus specimen CL 11.4 mm, 40 (yolky), size, 1.35 × 1.52 mm to 1.75 × 1.43 mm. Paralectotypes, CL 9.3 mm, 8 eggs, size, 1.43 × 1.48 mm to 1.48 × 1.52 mm; CL 10.3 mm, 18 eggs, size, 1.26 × 1.35 mm to 1.30 × 1.12 mm.

Hosts: The R/V Nautilus specimen was found associated with the alcyonacean coral Chrysogorgia sp. The Albatross specimens collected in the Galapagos between Santa Cruz and San Cristobal Islands (Baba & Lin 2008) were also found on Chrysogorgia fruticola (Studer, 1894) .

Remarks. The R/V Nautilus specimen of U. occidentalis agrees well with the type specimens. However, the larger ovigerous female paralectotype, CL 10.3 mm, has P2–4 more slender than those of the other specimens (see the length-breadth ratios under the description), and P1 longer (5.3 versus 3.8–4.3 × carapace length), with the merus much longer than those of the others (1.3 versus 0.9–1.0 × carapace length) and the carpus and palm more depressed dorsoventrally (height 0.6 versus 0.8 × breadth). Inasmuch as there are no other morphological characters to discriminate this unusual form from the others, the above differences are regarded as individual variations.

Baba & Lin (2008) noted that the Albatross material of U. occidentalis from the Galapagos Islands has the ultimate flexor spine of the P2–4 dactyli more slender than the penultimate. This feature, however, is not consistent in the present material. The ultimate spine is subequal to the penultimate on P 2–4 in the R/V Nautilus specimen and the smallest male paralectotype, subequal on P2 and slightly narrower on P3 and P 4 in the other types. In addition to this inconsistency, the variability in both the size of the antennal scale and the direction of the rostrum displayed by the present material does not support the distinguishing characters discussed by Baba & Lin (2008) between U. occidentalis and U. orientalis Baba & Lin, 2008 from Taiwan. These two species resemble each other in nearly all aspects, except that sparse tubercles are present on the hepatic and lateral branchial regions in U. orientalis , absent in U. occidentalis . Given their disjunct distribution, it is unlikely that these are conspecific. Further studies are required to assess these differences.

Distribution. Off Panama [east of Punta Mala], the Galapagos Islands between Santa Cruz and San Cristobal Islands and now at East Wolf Seamount; at depths of 717– 873 m. The Albatross material reported by Baba & Lin (2008) was taken by the Albatross Station 2818, the location being the same station as the type locality of Sternostylus defensus (see below).


Museum of Comparative Zoology


Instituto de Zoologia














Uroptychus occidentalis Faxon, 1893

Baba, Keiji & Wicksten, Mary K. 2019

Uroptychus nitidus occidentalis

Faxon, W. 1895: 101
Faxon, W. 1893: 192