Uroptychus spinulosus, Dong, Dong & Li, Xinzheng, 2015

Dong, Dong & Li, Xinzheng, 2015, Galatheid and chirostylid crustaceans (Decapoda: Anomura) from a cold seep environment in the northeastern South China Sea, Zootaxa 4057 (1), pp. 91-105 : 98-102

Uroptychus spinulosus n. sp.

( Figs. 5 , 8 E)

Material examined. Holotype: Cold seep, ridge between continental shelf and slope, off Guangdong Province, China, southwest of Taiwan Island, northeastern South China Sea, MBM189177, 119 °17.137’E, 22°6.927’N, male (PCL 3.7 mm), 1121 m, coll. Jiaolong manned submersible of R/V Xiangyanghong 9, 9 July 2013.

Diagnosis. Carapace excluding rostrum slightly broader than long; lateral margins distinctly convex, with small anterolateral spine and additional spine at base of anterior cervical groove, posterior half with posteriorly diminishing spines; dorsal surface with transverse row of indistinct epigastric spines or rugae. Rostrum triangular, margins armed with 2 denticles on each side. Sternite 3 with anterior margin concave, unarmed. Antennal scale reaching distal end of ultimate peduncle article. Pereopod 1 merus and carpus each armed with 5 spines on distal margins, surfaces with longitudinal rows of tubercles on surface, tubercles distinctly elevated and tapering like spinules on dorsal surface, and relatively low or flattened on lateral, mesial and ventral surfaces. Pereopods 2–4 propodi distinctly broadened distally, flexor margin with 6 movable corneous spines including distal pair; dactyli moderately curving, ending in strong claw, flexor margin with 4–5 corneous spines.

Description. Carapace ( Fig. 5 A) (excluding rostrum) slightly broader than long. Lateral margins distinctly convex, each armed with strong anterolateral spine, and additional small spine at base of anterior cervical groove; posterior branchial margin (posterior half of lateral margin) armed with posteriorly diminishing spines. Rostrum broad, triangular, approximately 0.6 times as long as remaining carapace, margins armed with 2 denticles on each side. Outer orbital angle triangular. Dorsal surface of carapace armed with row of indistinct epigastric spines or rugae bearing fine setae. Pterygostomian ( Fig. 5 B) armed with 2 small spines anteriorly, anterior angle sharp.

Sternal plastron ( Fig. 5 C) slightly broader than long, widening posteriorly, lateral lobes with margins slightly serrated. Sternite 3 with anterior margin broadly concave, unarmed, median notch indistinct. Sternites 5–7 each with transverse, shallow grooves on ventral surface.

Abdominal tergites glabrous and unarmed; first segment with dorsal surface transversely ridged. Telson ( Fig. 5 D) distinctly broader than long; distal portion about 1.4 times as long as proximal portion, distal margin serrated, weakly concave.

Eyestalk nearly reaching to half rostrum length; cornea not dilated.

Basal article of antenna ( Fig. 5 E) short. Article 2 with triangular distolateral angle. Penultimate and ultimate article of antenna each armed with ventral distomesial spine, invisible on dorsal view; ultimate article about 1.7 times as long as penultimate article. Antennal scale subtriangular, 3.7 times as long as broad, reaching distal end of ultimate peduncle article. Peduncle extending to distal third of rostrum. Flagellum about twice as long as peduncle.

Third maxilliped ( Fig. 5 F) slender; ischium with well-developed crista dentata ( Fig. 5 G) along almost entire length; merus slightly serrated on distoflexor margin and armed with 1 disto-extensor spine; dactylus, propodus and carpus unarmed.

Pereopods 1 (P1, chelipeds) ( Fig. 5 A, H) subequal, 3.7 times as long as carapace (excluding rostrum); surface of each segment thickly bearing long and soft setae. Ischium short, lateral margin armed with strong proximal spine, mesial margin armed with acute distal spine and 2 small proximal spines. Merus subcylindrical, about 0.9 times as long as carapace (excluding rostrum), armed with coniform spinules arranged in longitudinal rows on dorsal surface, such spinules flattened or degenerated as low tubercles or rugae on lateral, mesial, and ventral surfaces; ventral surface with distinctly elevated and marginally serrated protuberance on center part; mesial surface armed with strong middle spine; distal margins armed with 5 spines including 1 ventral lateral spine, 2 (dorsal and ventral) mesial spines and 2 small median dorsal spines. Carpus subcylindrical, equal in length to merus, surface armed with longitudinal rows of spinules or rugae as distributed on merus; mesial surface armed with longitudinal row of 3 small spines on proximal half; distal margins armed with 5 spines including 1 median dorsal spine, 2 (dorsal and ventral) mesial spines, and 2 (dorsal and ventral) lateral spines. Propodus palm relatively compressed, about 4.8 times as long as broad, 1.7 times as long as carapace (excluding rostrum), and 2.5 times as long as dactylus, dorsal surface with faint short striae. Fingers (dactylus and fixed finger) ( Fig. 5 I) crossing distally; occlusal margins finely denticulate, with low submedian tooth on dactylus.

Pereopods 2–4 (P2–4, ambulatory legs) ( Fig. 5 J–L) sparsely setose on each segment (especially on extensor margins). Meri about 3.7–4.4 times as long as broad, decreasing in length from P2 to P4; extensor margin each armed with small distal spine, and 1 or 2 indistinct proximal spines on P2 and P3; flexor margin each armed with small distal spine. Carpi with margins unarmed, each about half P2 merus length. Propodi distinctly broadened distally, each about 0.9 P1 merus length; flexor margin armed with 6 movable corneous spines including distal pair, proximalmost spine separately located on proximal one-third and other spines densely placed on distal projection. Dactyli ( Fig. 5 M) each about 0.6 propodi length, moderately curving, ending in strong claw; flexor margin armed with 4–5 corneous spines.

Habitat. Cold seep sediments.

Distribution. Northern South China Sea.

Etymology. The specific name is derived from the Latin spinula, meaning diminutive spine, alluding to the many spinules on the surfaces of cheliped merus and carpus.

Remarks. Uroptychus spinulosus n. sp. is closely related to U. hamatus Khodkina, 1981 (see Zarenkov & Khodkina 1981), U. insignis ( Henderson, 1885) and U. zeidleri Ahyong & Poore, 2004 in having spinulose surfaces of the cheliped merus and carpus, and sharing the similar shape of the P2–4 propodus and dactylus. Uroptychus spinulosus n. sp. differs from the latter three in having smooth hepatic margins, whereas the latter three bear spine(s) or subtle denticles on the hepatic margins. Uroptychus spinulosus n. sp. further differs from U. hamatus in having a transverse row of epigastric spines and relatively shorter anterolateral spines; in U. hamatus , the dorsal surface of the carapace is unarmed, and the anterolateral spines are relatively long nearly reaching distal margins of eyestalks. Uroptychus spinulosus n. sp. further differs from U. insignis in having cheliped merus armed with single strong spine on mesial margin (excluding the mesiodistal one), and P2–4 propodus bearing another corneous spine on proximal one-third of the flexor margin; in contrast, U. insignis has cheliped merus armed with several strong spines on mesial margin, and P2–4 propodus bearing corneous spines only on distal projection ( Ahyong et al. 2015). Uroptychus spinulosus n. sp. further differs from U. zeidleri in having unarmed second article of antennal peduncle and extensor margins of the P2–3 carpi, and the first branchial marginal spine separated far from the remainder; in U. zeidleri , the second article of antennal peduncle bears an outer spine, the extensor margins of the P2–3 carpi are spinulose, and all the branchial marginal spines are closely spaced.

Uroptychus spinulosus n. sp. also resembles U. ensirostris Parisi, 1917 , U. subsolanus Ahyong & Poore, 2004 and U. xipholepis Van Dam, 1933 in having spinose distal margins of the cheliped meri and carpi, practically unarmed extensor margins of the P2–4 meri and carpi, and sharing the similar shape and armature of the P2–4 propodus and dactylus. Uroptychus spinulosus n. sp. is readily distinguished from the other three by the coniform spinules on the dorsal surfaces of the cheliped meri and carpi, rather than having the scale-like granules ( U. ensirostris ) ( Froglia 1987) or being unarmed ( U. subsolanus and U. xipholepis ); and the antennal scale reaching to the distal end of the peduncle, instead of extending shorter ( U. ensirostris and U. xipholepis ) or distinctly longer ( U. subsolanus ) than the distal end of the antennal peduncle. Uroptychus spinulosus n. sp. further differs from U. subsolanus and U. xipholepis by having a row of epigastric spines, whereas the latter two an unarmed dorsal surface of the carapace.

Figures

FIGURE 5. Uroptychus spinulosus n. sp., holotype, MBM 189177, male PCL 3.7 mm. A, carapace, abdominal tergites 1 – 3 and right cheliped, dorsal view; B, right pterygostomian, lateral view; C, sternal plastron, ventral view; D, telson, dorsal view; E, left antennal peduncle, ventral view; F, left third maxilliped, ventral view; G, right crista dentate, ventral view; H, right cheliped (excluding chela, setae omitted), ventral view; I, right cheliped fingers (setae omitted), dorsal view; J, right pereopod 2, lateral view; K, right pereopod 3, lateral view; L, right pereopod 4, lateral view; M, dactylus and distal propodus of right pereopod 2, lateral view. Scales equal 1.0 mm.

FIGURE 8. Specimens conserved in ethanol. A, Munidopsis lauensis Baba & de Saint Laurent, 1992, MBM 189173, ovig. female, PCL 13.9 mm; B, Munidopsis tuberosa Osawa, Lin & Chan, 2008, MBM 189175, male, PCL 6.3 mm; C, Munidopsis verrilli Benedict, 1902, MBM 189174, female, PCL 20.8 mm; D, Uroptychus jiaolongae n. sp., holotype, MBM 189176, ovig. female, PCL 8.4 mm; E, Uroptychus spinulosus n. sp., holotype, MBM 189177, male PCL 3.7 mm.