Uroptychus anatonus, Baba, Keiji & Lin, Chia-Wei, 2008

Baba, Keiji & Lin, Chia-Wei, 2008, Five new species of chirostylid crustaceans (Crustacea: Decapoda: Anomura: Chirostylidae) from Taiwan, Zootaxa 1919, pp. 1-24 : 9-12

Uroptychus anatonus sp. nov.

( Figs. 6 , 7 , 13 B)

Type matrial. Holotype: NTOU A00852 , male (11.1 mm), South China Sea SW of Taiwan, Stn CD321, 20°43.053’N, 117°33.258’E, 951–973 m, 19 Aug 2005, collected together with many Nematocarcinus spp., Plesionika nessisi and Uroptychus orientalis sp. nov.

Diagnosis. Carapace as long as broad, granulose on dorsal surface, with strong anterolateral spine. Pterygostomian flap strongly angular anteriorly, ending in sharp spine. Excavated sternum anteriorly angular between close bases of Mxp1, with small spine in center. Sternite 3 with submedian spines contiguous to each other. Sternite 4 with prominent anterolateral process overreaching sternite 3. Abdomen granulose on somites 1–2. Antennal article 2 with distinct spine; antennal scale terminating in distal end of article 5; articles 4 and 5 unarmed; article 5 twice as long as article 4. Mxp3 unarmed on merus and carpus. P1 relatively massive, ischium without subterminal spine on ventromesial margin. Merus slightly longer than carapace. P2–4 meri successively shorter and narrower posteriorly; P2 merus much shorter than carapace; carpi subequal on P2 and P3, shortest on P4, length more than half that of propodus; propodi somewhat convex on flexor distal margin, ending in pair of spines preceded by 7, 5 or 6, 4 spines on P2, P3, P4 respectively; dactyli 0.7 length of carpi, flexor margin curved at proximal portion, with 8 or 9 proximally diminishing subtriangular spines.

Description. Carapace as long as broad, greatest breadth measured at posterior fourth of length. Dorsal surface granulose, moderately convex from side to side and from anterior to posterior end, continuously sloping down anteriorly to rostral tip. Gastric and cardiac regions indistinct, not separated by depression. Lateral margins convexly divergent posteriorly, with short granulate ridges representing feebly crenulations in dorsal view. Anterolateral spine strong, directed forward, overreaching antennal article 2. Rostrum somewhat deflexed anteriorly, sharp triangular, with interior angle of 24°. Dorsal surface flattish; length 0.44 that of rest of carapace. Lateral orbital angle with small spine. Pterygostomian flap granulose on surface, anteriorly ending in strongly produced spine.

Excavated sternum anteriorly sharp, angular; surface with small median spine. Sternal plastron 0.84 as long as broad, lateral extremities gently divergent posteriorly. Sternite 3 strongly depressed from level of sternite 4, anterior margin excavated in broad V-shape, with 2 submedian spines placed close to each other, but without notch between extending posteriorly beyond bases of spines; anterolateral angle rounded, anterolateral margin with blunt spine on each side. Sternite 4 with prominent anterolateral spine directed straight forward, overreaching sternite 3; anterolateral margin nearly straight, twice as long as posterolateral margin; surface with scattered tubercles.

Abdomen granulose on somites 1–2, on anterior part only on somite 3, smooth elsewhere. Somite 1 gently convex from anterior to posterior, without transverse ridge. Pleuron of somite 2 having lateral margins gently concave, divergent posteriorly, leading to blunt posterolateral margin. Pleura of somites 3–5 blunt or rounded, not sharp angular. Telson half as long as broad; posterior lobe 1.7 times longer than anterior lobe, posterior margin weakly emarginate.

Eyes reaching distal 1/4 of rostrum, twice as long as broad, lateral margins subparallel; cornea as long as peduncle.

Ultimate article of antennule 2.2 times longer than broad. Antennal peduncle ending in corneal distal margin. Article 2 with distinct spine. Antennal scale twice as broad as article 5, terminating at distal end of article 5. Distal 2 articles unarmed. Article 5 twice length of article 4, breadth half that of antennular ultimate article. Flagellum consisting of 21 segments, not reaching end of P1 merus.

Mxp1 with bases close to each other. Mxp3 barely setose on lateral surface. Basis with 3 denticles distally. Ischium having flexor margin without rounded distal end, crista dentata with 28 denticles. Merus moderately ridged along flexor margin, unarmed. Carpus unarmed.

P1 relatively massive, 4.8 times longer than carapace, barely setose except for fingers. Ischium with short dorsal spine, ventral surface tuberculose on mesial half, without subterminal spine. Merus 1.1 times longer than carapace, ventral surface with small spines and granules. Carpus broken on left and right side, length 1.28 (left) or 1.30 (right) times that of merus, ventral surface with tubercles and granules. Palm 2.0 (left) or 2.3 (right) times longer than broad, 0.68 (left) or 0.67 (left) length of carpus, ventral surface smooth. Fingers gaping on proximal 2/3, fitting on distal third, distally incurved. Movable finger 0.7 length of palm, opposable margin with 2-toothed process proximal to midlength of gaping margin.

P2–4 moderately compressed mesiolaterally. Meri successively shorter posteriorly (P3 merus 0.9 P2 merus, P4 merus 0.8 P3 merus), successively slightly narrower posteriorly; length-breadth ratio, 4.0 on P2, 3.8 on P3, 3.3 on P4; merus-propodus length ratio, 1.12 on P2, 1.00 on P3, 0.87 on P4; P2 merus 0.73–0.76 length of carapace. Meri and carpi unarmed. Carpi subequal on P2 and P3, shortest on P4 (0.88 that of P3); carpuspropodus length ratio, 0.59 on P2, 0.58 on P3, 0.53 on P4. Propodi subequal on P2 and P3, slightly shorter on P4; length-breadth ratio, 4.7 on P2, 4.6 on P3, 4.4 on P4; flexor margin somewhat convex on distal portion, ending in pair of spines preceded by 7, 5 or 6, 4 spines on P2, P3, P4 respectively. Dactyli subequal, length 0.39 that of propodus on P2–4, 0.66 that of carpus on P2–3, 0.73 on P4; flexor margin strongly curving at proximal third, with 8 or 9 proximally diminishing triangular spines, ultimate slightly broader than penultimate.

Color in life. Dark pale orange overall.

Etymology. From the Latin anatonus (extending forward), referring to the prominent processes of sternite 4 extending forward to overreach the anterior end of sternite 3, characteristic of the new species.

Remarks. The new species resembles U. brucei Baba, 1986 and U. maori Borradaile, 1916 and U. anacaena sp. nov. in granulose carapace. It is distinguished from these three species by a strong process on the anterolateral angle of sternite 4 that overreaches the anterior end of sternite 3, the antennal scale fully reaching instead of falling short of the end of article 5, the pterygostomian flap anteriorly sharp and angular, ending in a strong spine instead of weakly angular ending in a small spine. Uroptychus brucei is different from the other species in bearing a subterminal spine on the mesial margin of P1 ischium.

Distribution. South China Sea southwest of Taiwan, 951– 973 m.

Figures

FIGURE 6. Uroptychus anatonus sp. nov., holotype, male, NTOU A 00852. A, carapace and anterior part of abdomen, proximal part of left P 1 included, dorsal. B, same, lateral. C, sternal plastron, with excavated sternum, proximal part of Mxp 1 included. D, telson. E, antenna, left, ventral. F, Mxp 3, left, ventral. G, same, lateral. Scales for A, B = 5 mm; scales for C – G = 1 mm.

FIGURE 7. Uroptychus anatonus sp. nov., holotype, male, NTOU A 00852. A, P 1, proximal part, right, ventral. B, same, carpus, lateral. C, same, distal part, dorsal. D, P 2, right, lateral. E, same, distal, setae omitted, lateral. F, P 3, right, lateral. G, P 4, right, lateral. H, same, distal part, lateral. Scales for A – D, F – G = 5 mm; scales for E, H = 1 mm.

FIGURE 13. A, Uroptychus anacaena sp. nov., holotype, male (9.7 mm), NTOU A 00851. B, Uroptychus anatonus sp. nov., holotype, male (11.1 mm). C, Uroptychus orientalis sp. nov., holotype, ovigerous female (11.2 mm), NTOU A 00853. D, Uroptychus singularis sp. nov., paratype, female (8.0 mm), NTOU A 00868.