Heteroptychus scambus ( Benedict, 1902 )

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 : 597-601

Heteroptychus scambus ( Benedict, 1902)

Figures 302-304

Uroptychus scambus Benedict, 1902: 297 , fig. 41. — Baba 2009: 59 (part; see below under Remarks). Uroptychus glyphodactylus MacGilchrist, 1905:249 — Alcock & MacGilchrist 1905: pl. 70, fig. 4; pl. 71, figs 1, 1a, 1b, 1c, 1d. Not Uroptychus scambus — Baba 2005: 58 (= H. lemaitrei n. sp.). — Baba et al. 2009: 59, figs 49-50. (part = H.claudeae n. sp.).

Identification questioned: Uroptychus scambus — Doflein & Balss 1913: 134. — Van Dam 1937: 100, fig. 1. — Schnabel 2009: 567.

TYPE MATERIAL — Holotype: Japan, off Honshu , 617 m [2 miles off Entr. Port Heda, N 86° E], ov. female ( USNM 26165 ). [examined].

MATERIAL EXAMINED — Holotype: Japan, off Honshu. ALBATROSS Stn 3706,617 m [2 miles off Entr. Port Heda, N 86° E], ov. ♀ 3.8 mm ( USNM 26165 ). Taiwan. TAIWAN Stn CD 141, 22°12.04’N, 119°59.96’E, 1110- 985 m, 24.IX.2001, 1 ♂ 4.3 mm ( NTOU).

DISTRIBUTION„ Japan, 617 m, and Taiwan, 1110- 985 m.

DESCRIPTION OF HOLOTYPE (female) „ Carapace: 0.7 × as long as broad, greatest breadth mesured at posterior third, 2.5 × distance between anterolateral spines. Dorsal surface polished, moderately convex from anterior to posterior, ridged along posterior half of lateral margin. Lateral margin strongly convex posteriorly; anterolateral spine prominent, directed anteromesially, reaching distal quarter of rostrum. Rostrum broad triangular, with interior angle of 53°, half as long as broad, less than 0.2 × length of remaining carapace, straight horizontal, barely reaching tip of eye, dorsal surface flattish but feebly concave basally. Lateral limit of orbit with very small spine. Pterygostomian flap very low on posterior half (posterior height 0.3 × anterior height), anteriorly produced to sharp spine; anterior surface well inflated (convex from dorsal to ventral), with 3 small, low, blunt processes or protuberances.

Sternum: Excavated sternum bluntly produced anteriorly, surface with sharp ridge in midline on anterior half. Sternal plastron half as long as broad, lateral extremities convexly divergent posteriorly, sternite 6 broadest; left and right parts of sternites 5-7 discontinuous, interrupted by loss of median parts; anterior margin of sternite 3 deeply excavated in semicircular shape, with small median notch.

Abdomen: Smooth and polished. Somite 1 tergite gently convex dorsally from anterior to posterior. Somite 2 tergite 3 × broader than long; pleural lateral margin moderately concave, strongly divergent posteriorly, ending in blunt tip. Pleura of somites 3-4 ending in rounded margin. Telson 0.34 × as long as broad; posterior plate nearly transverse on posterior margin, length subequal to that of anterior plate.

Eyes: About 2 × as long as broad, subovate. Cornea slightly shorter than (0.8 x) remaining eyestalk.

Antennule and antenna: Ultimate article of antennular peduncle 3.3 × longer than high. Antennal peduncle relatively short and slender. Article 2 without lateral spine. Antennal scale articulated, slightly narrower than article 5, slightly overreaching midlength of article 4. Distal 2 articles unarmed; article 5 as long as article 4, breadth 0.6 × height of ultimate antennular article. Flagellum of 14 segments directed posteriorly.

Mxp: Mxp1 with bases moderately separated. Mxp3 basis with 2 obsolescent denticles on mesial ridge. Ischium 0.4 × as long as merus, crista dentata unarmed, flexor margin not rounded distally. Merus relatively thick mesio-laterally, with rounded ridge along flexor margin, unarmed. No spine on carpus.

P1: Left P1 missing. Right P1 smooth and glabrous except for fingers, 5.9 × longer than carapace. Ischium with basally broad, distally blunt distodorsal process and lobe-like proximal process overhanging basis. Merus with 2 distodorsal spines, length 1.4 × that of carapace. Carpus 1.4 × longer than merus, with row of several obsolescent blunt spines along distal half of mesial margin. Palm 3.8 × longer than broad, 0.6 × as high as broad, 0.8 × length of carpus; mesial margin roundly ridged, not cristiform. Fingers gaping proximally, straightly fitting to each other in distal third when closed, relatively slender, distally spooned; opposable margin of movable finger with prominent, distally blunt subtriangular process at proximal third, distal to position of opposite process of on fixed finger.

P2-4: Only right P4 available, setose along prehensile margins of propodus and dactylus. Merus 2.6 × longer than broad, 0.6 × length of propodus. Carpus slightly less than 0.4 × length of propodus. Propodus 1.4 × longer than dactylus, flexor margin concavely curving in lateral view. Dactylus 2 × length of carpus, 0.7 × length of propodus, flexor margin with row of 14 sharp spines proximally diminishing and nearly perpendicular to margin, ultimate and penultimate spines subequal.

Eggs. Number of eggs carried, 8; size, 1.26 × 1.46 mm - 1.23 × 1.50 mm.

REMARKS„ This species is characterized by the antennal scale articulated with the antennal article 2 and the broad triangular rostrum far falling short of the tip of the eye, both of which are possessed only by H. glyphodactylus (Mac- Gilchrist, 1905) from east of Andaman Islands. Because of the brevity of the original description of H. glyphodactylus and because its type material is hardly accessible, further comparison between the two nominal species is impossible. Therefore these species are treated as identical for the time being, although it is highly probable that they are different because of their disjunct distribution.

Uroptychus edwardi Kensley, 1977 from the western Indian Ocean off South Africa (holotype, ovigerous female, SAF A16033) was synonymized with U. scambus in my earlier paper ( Baba, 1988). However, the following characters are distinctive in H. edwardi : the spiciform rostrum overreaching the eyes, the anterolateral spine of the carapace directed straight forward, reaching the tip of the eye, and the frontal margin somewhat sinuous between the spiciform rostrum and the anterolateral spine [with no distinct lateral orbital spine]. Hence, the species is now resurrected.

The specimens reported under Uroptychus scambus from Japan ( Baba 1981) are referable to H. claudeae n. sp., as also are the female from Albatross Station 5605 ( Indonesia) and the two specimens from Station 5083 ( Japan) ( Baba 1988); the other specimen from the Albatross Station 4959 ( Japan) requires reexamination. The two specimens taken at Galathea Station 453, Makassar Strait ( Baba 2005) are referred to H. lemaitrei n. sp. (see above).

The NTOU material from Taiwan ( Baba et al. 2009) was reexamined. The male collected at Taiwan Station CD141 (222°12.04’N, 119°59.96’E, 1110- 985 m) may be referable to H. scambus , and the other specimens (except for the material from Station PCP342 that was not located) are identified with H. claudeae n. sp. (see above). This male ( Figure 304 ) is not in complete agreement with the holotype in having the rostrum distally narrower and directed somewhat dorsally, and in having the antennal article 2 with a small distolateral spine and the scale barely reaching the midlength of article 4. These subtle differences are regarded as individual variations. The terminal spines of P1 merus and carpus are stronger, probably sex-related. P2-4 are as illustrated (P2 and P3 are missing in the holotype), with no clear difference from those of all the other species.

Records of U. scambus reported by Doflein & Balss (1913: 134), Van Dam (1937: 100, fig. 1), and Schnabel (2009: 567) require verification.

Figures

FIGURE 302 Heteroptychus scambus (Benedict,1902),holotype of Uroptychus scambus, ovigerous female 5.7 mm (USNM 26165).A, carapace and anterior part of abdomen, dorsal.B, same,lateral.C, carapace,anterior part, dorsal. D, left pterygostomian flap,dorsolateral. E,sternal plastron,with excavated sternum and basal parts of Mxp1.F, right pleuraof abdominal somites 2-5,dorsolateral.G,telson. H, left antenna, ventral.I, left Mxp3, ventral.J, same, setae omitted, lateral.Scale bars:1 mm.

FIGURE 303 Heteroptychus scambus (Benedict, 1902),holotype of Uroptychus scambus, ovigerous female 5.7 mm (USNM 26165).A, right P1, dorsal. B, same, mesial.C, same, proximal part, lateral. D, same, ischium and merus, ventral. E, same, carpus, ventral.F, right P4, lateral.G, same,distal part,setae omitted. Scale bars:1 mm.

FIGURE 304 Heteroptychus scambus (Benedict,1902),male 4.3 mm,from Taiwan Stn CD141.A, carapace and anterior part of abdomen,dorsal. B, same, lateral.C, left antenna, ventral. D, right P1, dorsal. E, same, mesial.F, right P2, lateral.G, left P2, distal part, setae omitted, lateral.H, right P3,setae omitted,lateral.I, right P4, lateral.Scale bars: 1 mm.