Uroptychus faxianae, Dong & Gan & Li, 2021

Dong, Dong, Gan, Zhibin & Li, Xinzheng, 2021, Descriptions of eleven new species of squat lobsters (Crustacea: Anomura) from seamounts around the Yap and Mariana Trenches with notes on DNA barcodes and phylogeny, Zoological Journal of the Linnean Society 192 : -

UROPTYCHUS FAXIANAE SP. NOV.

( FIGS 5, 6)

Zoobank registration: urn:lsid:zoobank.org:act:5267D7D3-BF8C-4047-B652-1E515951DD23

Material examined: Holotype, MBM286633 , one male ( PCL 5.0 mm), stn. FX-DIVE 143, M4 seamount located on the Caroline Plate , West Pacific, 10°30’N, 140°09’E, 520–862 m, coll. Faxian ROV on R / V Kexue, 26 August 2017.

Description: Carapace (excluding rostrum) slightly longer than broad. Outer orbital angle with tiny spine. Lateral margins slightly convex, broadest at posterior branchial margin; anterolateral spine strong, lateral to and distinctly over-reaching outer orbital angle; hepatic margins unarmed; anterior and posterior branchial margin uneven, shallowly ridged. Posterior margin slightly concave. Dorsal surface glabrous, hairless. Rostrum triangular, as long as broad, approximately 0.3 times of remaining carapace length and 0.4 times of carapace breadth; dorsal surface glabrous; lateral margins unarmed. Pterygostomial flap with blunt anterior end; surface grabrous.

Sternal plastron broader than long. Sternite 3 with surface depressed; anterior margin concave, with narrow median notch and pair of (left spine might be missing) submedian spines; lateral margin with small denticle.Sternite 4 shallowly depressed on anterior part, with pair of transverse ridges medially; anterolateral corner produced, reaching bases of submedian spines of sternite 3; anterolateral margin straight, 1.2 times posterolateral margin length. Sternites 5–7 with transverse ridges interrupted by midline groove.

Abdominal tergites glabrous and unarmed.

Telson approximately 1.8 times broader than long; distal portion 1.5 times proximal portion length.

Eyestalk broad, reaching distal 0.2 of rostrum; lateral margins of peduncles slightly convex; cornea not dilated, approximately 0.3 times of remaining peduncle length.

Antennal peduncle reaching distal 0.2 of rostrum. Article 2 with triangular distolateral tooth. Article 4 and 5 unarmed; article 5 approximately 2.4 times of the length of article 4. Antennal scale dagger-shaped, approximately 2.9 times as long as broad, subequal in breadth with article 4, reaching midlength of article 5.

Third maxilliped slender, each article glabrous on ventral surface. Basis with two denticles on mesial ridge. Ischium slightly shorter than merus; crista dentata with about 19 denticles. Merus unarmed on flexor and extensor margins. Carpus short.

P1 subequal, approximately 3.4 times PCL; merus, carpus and palm glabrous and unarmed. Ischium armed with dorsodistal spine; ventrodistal margin unarmed. Merus 0.8 times PCL, 3.2 times longer than broad, broaden distally. Carpus subcylindrical, longer than merus, as long as PCL, 3.3 times longer than broad. Palm as long as carpus, 2.8 times longer than broad, relatively broader than merus and carpus. Fingers setose distally, approximately half of palm length; tips acute, slightly crossing over each other; occlusal margins minutely denticulate, slightly convex on fixed finger, and bearing broad, subrectangular tooth on base of dactylus.

P2–4 slender. Ischia short and unarmed. Meri laterally compressed, decreasing in length and subequal in breadth from P2 to P4; P2 merus 0.8 times PCL and 5.6 times longer than broad, P3 merus 0.8 times P2 merus length, P4 merus 0.7 times P2 merus length; extensor and flexor margins straight and unarmed. Carpi slightly decreasing in length from P2 to P4; P2 carpus 0.4 times PCL, P3 and P4 carpi approximately 0.9 times P2 carpus length; extensor and flexor margins unarmed. Propodi laterally compressed, distally setose, subequal in length and breadth from P2 to P4, 0.7 times PCL and 5.6 times as long as broad; flexor margin straight, with five or six corneous movable spines, including distal pair on distal half; distal pair adjacent to propodus–dactylus junction, penultimate spine closer to antepenultimate spines than to distal pair. Dactyli setose, approximately 0.4 times propodi length, slightly bent on proximal one-third; flexor margin with eight corneous spines evenly arranged on distal 0.7 part; distal two spines slender, subequal in breadth, distalmost spine longest, especially on P2 and P3, antepenultimate spine relatively shorter than penultimate spine, remaining spines small, bead-shaped and oriented somewhat parallel to flexor margin.

Habitat: Associated with golden coral Chrysogorgia sp.

Distribution: Seamount located on the Caroline Plate, West Pacific; depth 520– 860 m.

Etymology: The specific name is dedicated to the ROV Faxian, which collected the material.

Remarks: The new species closely resembles U. australis ( Henderson, 1885) , U. disangulatu s Baba, 2018 and U. brevirostris Van Dam, 1933 in having the carapace armed only with anterolateral spines, P1 unarmed and P2–4 dactyli bearing small spines oriented parallel to the flexor margin. Uroptychus faxianae can be distinguished from U. australis in having stronger anterolateral spines (over-reaching and located immediately lateral to the outer orbital angle) instead of small anterolateral spines (falling short of, and located posterior to, the outer orbital angle); rostrum relatively short instead of slender; antennal scale reaching midlength instead of over-reaching or slightly falling short of distal end of article 5; flexor spines on P2–4 dactyli evenly arranged instead of separated into groups (antepenultimate spine is remote from proximal spines); and the extensor margin of P2–4 meri unarmed instead of with small, often obsolescent denticles on proximal part. Uroptychus faxianae differs from U. disangulatu s in having apex of antennal scale acute instead of distally blunt and rounded, and having outer orbital angle armed with short spine instead of blunt and unarmed. Uroptychus faxianae differs from U. brevirostris in having relatively slender P1 (carpus 3.3 times longer than broad; palm 2.8 times longer than broad), slender P2–4 meri (P2 merus 5.6 times longer than broad), and a relatively longer rostrum distinctly over-reaching eyestalk (eyestalk reaching distal 0.2 of rostrum); whereas U. brevirostris has massive P1 (carpus 2.5 times longer than broad, palm 2.2 times longer than broad), stout P2–4 meri (P2 merus 3.5–3.6 times longer than broad) and a rostrum barely reaching or slightly over-reaching the eyestalk. Uroptychus faxianae further differs from U. australis and U. brevirostris in having small and bead-like spines on the P2–4 dactyli flexor margin and the anterior end of pterygostomial flap blunt; whereas the latter two species have longer spines on the P2–4 dactyli flexor margin and the anterior end of the pterygostomial flap with acute spine (Baba, 2018).

No COI or 16S sequence information for the closely related species was available for comparative analysis. The DNA sequences of the new species are provided in this study.