Monomia lucida, Koch & Ďuriš, 2018

Koch, Milan & Ďuriš, Zdeněk, 2018, Monomia lucida sp. nov., a new swimming crab (Crustacea: Decapoda: Portunidae) from the South China Sea, Zootaxa 4387 (3), pp. 567-579 : 569-576

Monomia lucida sp. nov.

( FIGS. 1–3 )

Portunus argentatus , STePHeNSON & ReeS 1967b: 11–13 (iN PArT), fig. 2A, e. [NOT Portunus argentatus A. MilNe-EdWArdS, 1861] Monomia argentata , CHerTOPrud et al. 2012: 313 (iN PArT), Pl. 51f. [NOT Portunus argentatus A. MilNe-EdWArdS, 1861]

Material examined. Holotype: ♂ CW 58.0 MM, MNHN-IU-2014-10082 [GENBANk N. MG563791 ], 6 SEP. 2013, FcN UO 76A-VN13.— Allotype: ♀ CW 50.5 MM, MNHN-IU-2014-10083 [GENBANk N. MG563793 ], 6 SEP. 2013, FcN UO 76A-VN13.— Paratypes: 1♀ CW 32.2 MM, MNHN-IU-2014-10084 AND 1♀ CW41.7 MM, MNHN-IU- 2014-10085 [GENBANk N. MG563794 ], FcN UO 76A-VN13.—1♀ CW 45.2 MM, NHMUK 2017.401, cOLOUR PHOtO, 30 Aug. 2013, fcn UO 60F-Vn13.—1♂ CW 42.5 mm, NHMUK 2017.402 [GenBank n. MG563792 ; G1 dissected FOR SEM], 27 JUL. 2012, FcN UO 12G-VN12. ALL cOLLEctED FROM CUǻ Bé FISHING PORt (12°20'6.92"N, 109°12'13.88"E), NORtH OF NHAtRANG, KHANH HOA PROVINcE, VIEtNAM, cOLL. M. KOcH, Z . ĎURIŠ.

Comparative material. Monomia argentata : Indonesia. 2♂♂ CW 33.2 MM [GENBANk N. KY524474 ], 35.5 MM [GENBANk N. KY524473 ] , 1♀ CW 38.0 MM [GENBANk N. KY524472 ], ZRC 2003.0522, StN EA-TT06, TELUk TAREMPA, ANAMbAS, 14 MAR. 2002 —1♂ CW 30.1 MM [GENBANk N. KY524476 ], 1♀ 36.2 MM [GENBANk N. KY524475 ], ZRC 2003.0523, StN EA-TT08, W. cOASt OF PULAU BUNGURARI, NAtUNA, 18 MAR. 2002. ALL cOLLEctED by EXPEDItION ANAMbAS 2002, cOLL. T. TAN et al., DEt. P.K.L. NG et al., NIGHt tRAWLS (StAtION DAtA: NG et al. 2004).

Vietnam. 1♂ CW 36.7 MM, MNHN-IU-2014-10072, 9 AUG. 2010, FcN UO 29F-VN10, cOLL. Z. ĎURIŠ, I. HORká.—1♂ jUVENILE CW 20.0 MM, MNHN-IU-2014-10073, 14 AUG. 2011, cOLL. M. KOcH.—1♀OV CW 35.3 MM, MNHN-IU-2014-10074 [GENBANk N. KY524477 ], 14 AUG. 2012, FcN UO-110J-VN12, cOLL. M. KOcH, Z. ĎURIŠ.— 1♂ CW 32.4 MM, MNHN-IU-2014-10075 [GENBANk N. KY524479 ], FcN UO-12I-VN12, cOLL. M. KOcH, Z. ĎURIŠ.— 1♂ CW 36.8 MM, MNHN-IU-2014-10076 [GENBANk N. KY524480 ], FcN UO-12I-VN12, cOLL. M. KOcH, Z. ĎURIŠ.— 1♂ CW 27.0 MM, MNHN-IU-2014-10077, 27 JUL. 2012, FcN UO-12I-VN12, cOLL. M. KOcH, Z. ĎURIŠ.—4♂♂ CW 22.8–35.5 mm; 2♀♀ CW 23.4, 32.9 mm; 2♀♀ov, CW 26.3, 37.8 mm; 3♀♀ subadult, CW 22–23.5 mm), 27 Jul. 2012, MNHN-IU-2014-10078, fcn UO-12I-Vn12, coll. M. Koch, Z. Ďuriš.—5♂♂ CW 22.8–30.4 mm; 2♀♀ CW 26.4, 31 mm; 2♀♀ov CW 26.6, 31.2 mm, 27 Jul. 2012, fcn UO 12I-Vn12, coll. M. Koch, Z. Ďuriš.—2♂♂ CW 31.0, 31.2 MM, 2♀♀OV, CW 29.5, 31.0 MM, 24 AUG. 2013, FcN UO-25D-VN13, cOLL. Z. ĎURIŠ, A. ŠObáňOVá.—1♀ CW 36.0 MM, IOM [GENBANk N. KY524478 ], 6 SEP. 2013, FcN UO-76E-VN13, cOLL. Z. ĎURIŠ, A. ŠObáňOVá. ALL cOLLEctED FROM CUǻ Bé FISHING PORt (12° 20' N, 109° 12' E), NORtH OFF NHAtRANG, KHANH HOA PROVINcE.

Taiwan. 1♂ CW 32.2 MM, 1♀OV CW 27.5 MM, 3♀♀ CW 34–42.1 MM, 3 SEP. 2012, UO-28F-TW12, cOLL. Z. ĎURIŠ. DONGGANG FISHING PORt, SW TAIWAN (24° 56' N, 121° 54' E) : 1♂ CW 36.4 MM, NMMBCD4072 [GENBANk N. KY524468 ], 8 SEP. 2012, FcN UO-88C-TW 2012, cOLL. Z. ĎURIŠ, C.-W. LIN.—1♀♀ CW 41.9 MM NMMBCD4073 [GENBANk N. KY524467 ], 8 SEP. 2012, FcN UO-88C-TW 2012, cOLL. Z. ĎURIŠ, C.-W. LIN.—2♂♂ CW 35.4, 35.5 MM, 2♀♀ CW 32.6, 40.2 MM, 8 SEP. 2012, UO-88C-TW 2012, cOLL. Z. ĎURIŠ, C.-W. LIN.—1♂ CW 37.2 MM, MNHN-IU-2014-10080 [GENBANk N. KY524470 ], 12 SEP. 2015, FcN UO-34-TW15, cOLL. Z. ĎURIŠ, A. ŠObáňOVá, C.-W. LIN.—1♂ CW 37.9 MM, MNHN-IU-2014-10081 [GENBANk N. KY524469 ], 12 SEP. 2015, FcN UO-34-TW15, cOLL. Z. ĎURIŠ, A. ŠObáňOVá, C.-W. LIN.—1♀,CW 38.9 MM, MNHN-IU-2014-10079 [GENBANk N. KY524471 ], 12 SEP. 2015, UO-34-TW15, cOLL. Z. ĎURIŠ, A. ŠObáňOVá AND C.-W. LIN.—1♀OV CW 31.0 MM, 2♀♀ CW 31.8, 36.6 MM, 12 SEP. 2015, FcN UO-34-TW15, cOLL. Z. ĎURIŠ, A. ŠObáňOVá, C.-W. LIN. ALL cOLLEctED FROM DASI FISHING PORt, NE TAIWAN (24° 56' N, 121° 54' E.

Monomia gladiator : 1♂ CW 34.5 MM, MNHN-IU-2014-10087 [GENBANk N. KY524466 ], 1♀ CW 32.0 MM, 27 JUL. 2012, FcN UO 12H-VN12, CUǻ Bé FISHING PORt (12°20'6.92"N, 109°12'13.88"E), NORtH OF NHAtRANG, KHANH HOA PROVINcE, Vietnam, cOLL. M. KOcH, Z. ĎURIŠ .

Monomia pseudoargentata : 1♂ CW 24.1 MM, MNHN-IU-2014-10086 [GENBANk N. KY524463 ], 14 AUG. 2012, FcN UO 110G2-VN12, CUǻ Bé FISHING PORt (12°20'6.92"N, 109°12'13.88"E), NORtH OF NHAtRANG, KHANH HOA PROVINcE, Vietnam, cOLL. M. KOcH, Z. ĎURIŠ .

Monomia samoensis : HOLOtyPE, jUVENILE ♂ CW 15.0 MM, AMNH 7482 , PAGO PAGO HARbOUR, Samoa, ON SURFAcE, 6 Oct. 1936 .

Description of holotype. CARAPAcE ( FIG. 2A ) tRANSVERSALLy HEXAGONAL, CL/CW RAtIO 0.6. FRONt WIDtH 0.14 OF CW, FRONtAL REGION INcLUDING INNER ORbItAL tOOtH 0.19 OF CW, FRONtO-ORbItAL WIDtH (bEtWEEN tIPS OF OUtER ORbItAL tEEtH) 0.40 OF CW. FRONt SUbDIVIDED INtO FOUR tEEtH—MEDIAN PAIR DIStINctLy SMALLER tHAN LAtERAL; MEDIAN SULcUS bEtWEEN MEDIAN tEEtH RUNNING VENtRALLy tO SPINIFORM PROjEctION OVERREAcHING FRONt, APPRESSED tO DIStINctLy SHORtER MEDIAN EPIStOMIAL tOOtH. SUPRAORbItAL MARGIN GRANULAtED, WItH ONE WELL DEVELOPED NOtcH IN MIDDLE, WItH tOOtH-LIkE ELEVAtION NEAR EXtRAORbItAL ANGLE; LAttER WItH ADDItIONAL tOOtH VENtRALLy. INNER ORbItAL ANGLE tOOtH-LIkE, WItH GLAbROUS VENtROMEDIAL LEDGE. INFRAORbItAL MARGIN WItH SHALLOW bROAD MEDIAN NOtcH; NARROW DEEP LAtERAL NOtcH. ANtEROLAtERAL MARGIN ARMED by NINE tEEtH WItH GRANULAtED MARGINS, FIRSt tOOtH LARGER WItH SINUOUS OUtER MARGIN, tEEtH 2–8 SUbEqUAL, SHARP, PROjEctING FORWARDS, tOOtH 9 LARGESt, PROjEctING LAtERALLy. POStEROLAtERAL MARGIN SLIGHtLy GRANULAtE, cONcAVE, SHORtER tHAN ANtEROLAtERAL MARGIN; POStEROLAtERAL ANGLE ROUNDED; POStERIOR MARGIN SLIGHtLy cONVEX.

CARAPAcE WItH DORSAL SURFAcE DENSELy cOVERED by SHORt PILA, REGIONS WELL DEFINED, ELEVAtED, DEMARcAtED by PAtcHES OF DIStINct kNOb-LIkE GRANULES; LEFt PROtOGAStRIc PAtcH OF GRANULES cONNEctED POStERO-MEDIALLy WItH MESOGAStRIc ONES (RIGHt ONE SEPARAtED FROM tHOSE); MESObRANcHIAL GRANULES SUbDIVIDED INtO FOUR PAtcHES; ANtEROLAtERAL REGION WItH 2 SUbMARGINAL GRANULAR PAtcHES; cARDIAc, LAtERAL POStcARDIAc, MEDIAN POStcARDIAc REGIONS EAcH WItH SIMPLE PAtcH OF GRANULES; ADDItIONAL OVAL PAtcH OF GRANULES ON EAcH SIDE OF cARAPAcE bEtWEEN LAtERAL POStcARDIAc REGION AND POStEROLAtERAL MARGIN.

MALE tHORAcIc StERNItES 1–4 DIStINctLy GRANULAtE; StERNItES 3, 4 FUSED, WItHOUt DIStINct SULcUS; StERNItE 4 WItH NARROW MEDIAN GROOVE, StERNItES 7, 8 FUSED MEDIALLy, SULcUS DIStINct ON EXPOSED OUtER HALF. LOckING MEcHANISM POStERO-MEDIALLy ON StERNItE 5 ON SIDES OF PLEONAL cAVIty; PAIR OF ELONGAtE, POStERIORLy DIREctED, DIStALLy DEPRESSED LObES REAcHING MIDDLE OF StERNItE 6, bOtH APIcES WItH ANtERIORLy DIREctED VENtRAL DENtIcLE; LAttER cORRESPONDING WItH PAIR OF ANtEROLAtERAL HOLLOWS ON INNER SIDE OF PLEOMERE 6.

PLEON ( FIG. 2B ) ‘T’-SHAPED, WItH PLEOMERES 3–5 FUSED, WItH bORDERS OF PLEOMERES DEMARcAtED by DIStINct tRANSVERSE GLAbROUS RIDGES, PLEOMERES 4, 5 EAcH WItH LONG tRANSVERSE RIDGE, DIStAL HALF OF PLEOMERE 5 AND PLEOMERE 6 WItH MEDIAN GLAbROUS RIDGE. TELSON NARROWLy tRIANGULAR, 1.5 tIMES LONGER tHAN bASAL WIDtH, WItH ROUNDED tIP, bROADLy ROUNDED POStERIOR MARGIN. SIXtH PLEOMERE 1.25 tIMES LONGER tHAN WIDE, 2.6 tIMES LONGER tHAN tELSON, LAtERAL MARGINS cONVEX, SUbPARALLEL, WItH bROADLy ROUNDED ANtEROLAtERAL ANGLES DIStINctLy REAcHING bEyOND bASE OF tELSON; PAIR OF ANtEROLAtERAL LOckING HOLLOWS ON INNER SIDE. SULcUS bEtWEEN PLEOMERES 4, 5 DIStINct, WItH PAIR OF DEEP SUbMEDIAN DEPRESSIONS; bORDER bEtWEEN PLEOMERES 4, 5 FEEbLy DEMARcAtED. POStERIOR MARGIN OF bODy (ON PLEOMERE 3) FORMING HIGH SHARP LAMINAR cRESt, INDIStINctLy SINUAtE MEDIALLy ON OUtLINE; LAtERAL MARGINS OF cRESt DEEPLy cONVEX, POStEROLAtERAL ANGLES ROUNDED. CRESt ON PLEOMERE 2 DIStINctLy LOWER tHAN ON PLEOMERE 3, POStERIOR MARGIN SINUAtE, tRIPLy cONVEX, WItH MEDIAN cONVEXIty MORE PRODUcED, LAtERAL MARGIN PRODUcED tO ELONGAtE tOOtH.

BASAL ANtENNAL SEGMENt WItH ELONGAtE LAtERAL LObE WItH bLUNt APEX ENtERING ORbItAL cAVIty.

THIRD MAXILLIPEDS ( FIG. 2C ) DIStINctLy GRANULAtE ON IScHIUM, MERUS, EXOPOD, WItH DENSELy PILOSE MARGINS; PALP tAPERING DIStALLy, SEGMENtS SUbcyLINDRIcAL; MERUS SLIGHtLy LONGER tHAN bROAD, LAtERAL, MEDIAL PARtS GLAbROUS, ANtEROLAtERAL ANGLE cREAtING tRIANGULAR PROjEctION; IScHIUM AbOUt 1.7 tIMES MERUS LENGtH, WItH LONGItUDINAL GLAbROUS GROOVE. EXOPOD StOUt, AbOUt HALF OF IScHIUM WIDtH, WItH SUbDIStAL tRIANGULAR PROjEctION ON MEDIAL bORDER; FLAGELLUM LONGER tHAN MERUS WIDtH. OtHER MOUtHPARtS NOt DISSEctED.

CHELIPEDS ( FIG. 2D ) SyMMEtRIcAL, RELAtIVELy RObUSt, LENGtH 0.8 OF MAXIMUM cARAPAcE WIDtH (INcL. LAtERAL tEEtH). MERUS WItH 4 SPINES ON ANtERIOR, 2 ON POStERIOR, bORDERS, WItH ANtERIOR ONE DEPRESSED, WItH SERRAtE ANtERIOR MARGIN. CARPUS WItH 1 SHARP INNER SPINE, 1 FLAttENED OUtER SPINE (LAttER DOUbLE ON LEFt cHELIPED); 2 DIStINct cARINAE ON DORSAL SURFAcE. UPPER SURFAcE OF PALM WItH 2 GRANULAR cREStS, INNER ONE ENDING by SPINE DIStALLy, OUtER SURFAcE WItH SMALL SPINIFORM tOOtH OVER ARtIcULAtION WItH cARPUS, WItH 2 GRANULAR cREStS ENDING ON LEVEL OF FINGER ARtIcULAtION, LOWER ARcHED, cREAtING OUtER VENtRAL, SHARPLy PRODUcED, MARGIN; INNER SURFAcE OF PALM WItH ObtUSE LONGItUDINAL kEEL DIVIDING VENtROMEDIAL AND FLAt VENtROLAtERAL SURFAcES; SURFAcES FINELy GRANULAtE, WItH GRANULES ORDERED tO LONGItUDINAL LINES OR SHORt tRANSVERSE SqUAMIFORM ROWS; FINGERS StRAIGHt, tAPERING DIStALLy (LEFt FIXED FINGER WItH bROkEN tIP IN HOLOtyPE), 0.7 OF MAXIMUM PALM LENGtH, DIStINctLy cARINAtE. RIGHt MOVAbLE FINGER WItH MOLARIFORM tOOtH PROXIMALLy ON cUttING EDGE; FINGERS OtHERWISE WItH SOME tRI- OR tEtRALObED SERIAL cONIcAL tEEtH.

AMbULAtORy LEG 5 WItH MERUS SERRAtE ON bOtH ANtERO- AND POStERODIStAL ANGLES. NAtAtORIAL DActyLUS OVAL, 2.2 tIMES LONGER tHAN MAXIMUM WIDtH, bROADLy ROUNDED DIStALLy, WItH LONGItUDINAL MEDIAN GROOVE, WItH WELL-DEFINED ROUNDED DARk SPOt DIStALLy; UPPER SURFAcE FINELy PILOSE, WItH 5 LONGItUDINAL GLAbROUS PAtHS—PAIRED SUbMEDIAN, MARGINAL, AND ADDItIONAL ONE cLOSE tO POStERIOR MARGINAL PAtH. PROPODUS WItH 4 LONGItUDINAL GLAbROUS PAtHS ON UPPER SURFAcE—3 ANtERIOR, 1 POStERIOR MARGINAL.

MALE G1 ( FIG. 3 AB) LONG, SLENDER; PROXIMAL PARt RObUSt, tAPERING DIStALLy, PROXIMOLAtERAL LObE SUbqUADRAtE, WItH POINtED ANtERIOR ANGLE; G1WItH REctANGULAR cURVAtURE IN AbOUt 2/3 OF LENGtH, DIStAL PARt ALMOSt UNIFORMLy SLENDER; APEX SLENDER, NOt EXPANDED, WItH ObLIqUE DIStOVENtRAL OPENING, SUbtRIANGULAR tIP.

Male paratype. MORPHOLOGIcALLy cONSIStENt WItH HOLOtyPE, SMALLER, CL/CW RAtIO 0.55. RIGHt cHELIPED WItH 5 ANtERIOR SPINIFORM tEEtH ON MERUS.

Female paratypes. FEMALES OF SMALLER SIzE tHAN HOLOtyPE MALE, CL/CW RAtIO 0.58, 0.56, 0.58 FOR FEMALES ORDERED by INcREASING SIzE, RESPEctIVELy. SHAPE IS cONSIStENt WItH tHAt OF MALES, EXcEPt SEcONDARy SEXUAL cHARActERS. PLEON tRIANGULAR WItH ALMOSt StRAIGHt SIDES IN tWO SMALLER FEMALES. PLEON OF LARGESt FEMALE bROADLy tRIANGULAR, LAtERALLy cONVEX, WItH DIStINct tRANSVERSAL RIDGE ON EAcH PLEOMERE 4, 5; PLEOMERE 6 bROADLy ROUNDED, ALMOSt SEMIcIRcULAR; tELSON SMALL, SLIGHtLy LONGER tHAN WIDE, WItH ROUNDED tIP. VULVAE ( FIG. 3D ) LOcAtED ON StERNAL SUtURES 5/6 ON SIDES OF PLEONAL cAVIty; MEDIAL (INNER) SIDE OF OVAL MARGIN INDIStINct, LAtERAL (OUtER) MARGIN DEFINED by PAIR OF cLOSELy SEt DIStINct ROUNDED tUbERcLES SUbDIVIDED by RESPEctIVE StERNAL SUtURE, tUbERcLES MEDIALLy OVERHANGING LAtERALLy DIREctED GONOPORE ON bOttOM OF VULVA.

Colouration. THE GENERAL cOLOUR OF tHE cARAPAcE AND cHELIPEDS IS yELLOWISH bROWN WItH RED AND WHItE PAtcHES OF GRANULES, WHIcH IS ALSO VISIbLE ON FRESHLy PRESERVED SPEcIMENS ( FIG. 1 ). SEGMENtS AND DActyLI OF tHE AMbULAtORy LEGS, INcLUDING cHELIPEDS, ARE PURPLE. THERE IS A RELAtIVELy SMALL bUt WELL-DEFINED ROUNDED DARk PURPLE SPOt WItH A WHItE OUtLINE ON tHE DIStAL END OF tHE DActyLUS OF tHE SWIMMING LEG. OUtER RIDGES OF tHE cHELIPEDS PALM, OUtER cARPAL tOOtH, AND PLEONAL cREStS ARE DIStINctLy IRIDEScENt.

Etymology. DUE tO tHE VERy StRIkING IRIDEScENcE OF VARIOUS bODy PARtS IN DAyLIGHt, tHE LAtIN WORD ‘ lucidus ’ (SHINy) IS PROPOSED FOR tHE SPEcIES NAME.

Remarks. SWIMMING cRAbS OF tHE GENUS Monomia GIStEL, 1848 ARE cHARActERISED by MODERAtELy bROAD ANtEROLAtERAL tEEtH, LARGE ORbItS ON tHE cARAPAcE, tHE bASAL ANtENNAL SEGMENt WItH A bLUNt LObIFORM LAtERAL PROcESS ENtERING tHE ORbIt, A SLIGHtLy PRODUcED EPIStOME, AND tHE DIStINct ANtEROLAtERAL ANGLE OF tHE MERUS OF tHE tHIRD MAXILLIPED (ALcOck 1899). THE GENUS Monomia cURRENtLy cONtAINS 12 SPEcIES (NG et al. 2008; KOcH et al. 2015) DIStRIbUtED IN tHE INDO-WESt PAcIFIc AREA.

SEVEN OF tHOSE SPEcIES ARE EASILy DIStINGUISHAbLE FROM M. lucida sp. nov.: M. rubromarginata (LANcHEStER, 1900), M. lecromi (MOOSA, 1996), AND M. calla KOcH, NGUyEN & ĎURIŠ, 2015, IN HAVING ONLy ONE tOOtH ON tHE POStERIOR bORDER OF tHE cHELIPED MERUS (LANcHEStER 1900; MOOSA 1996; KOcH et al. 2015), versus tWO tEEtH POStERIORLy ON tHE cHELIPED MERUS IN M. lucida sp. nov. Monomia petrea (ALcOck, 1899) POSSESSES A VERy LONG tOOtH ON tHE INNER SURFAcE OF tHE cHELIPED cARPUS, WHILE It IS SHORt IN M. lucida sp. nov. FOR M. euglypha (LAURIE, 1906), tHE SUbHEXAGONAL SHAPE OF ItS cARAPAcE WItH tHE DIStOLAtERAL MARGIN SINUAtE DUE tO A DIStINctLy bROADENED, POStERIORLy EXPANDED bASE OF tHE MOSt POStERIOR LAtERAL tOOtH, AND StRAIGHt, StOUt G1, ARE cHARActERIStIc (versus WItH AN ANtERIORLy SUbcIRcULAR cARAPAcE WItH A DEEPLy INcISED POStEROLAtERAL MARGINS DUE tO tHE cARAPAcE bEING StRONGLy NARROWED POStERIORLy tO tHE LEVEL OF tHE LAtERAL SPINES, AND StRONGLy cURVED AND SLENDER G1, IN M. lucida sp. nov.). Monomia curvipenis (StEPHENSON, 1961), AND M. australiensis (StEPHENSON & COOk, 1973) MAy ALSO bE DIStINGUISHED FROM tHE NEW SPEcIES by tHE SHAPE OF tHE G1; FURtHERMORE, tHE DIStAL PARt OF tHE MALE PLEON WItH tHE tELSON IS SHARPLy tRIANGULAR IN tHE tWO LAttER SPEcIES (versus PLEOMERE 6 WItH LAtERAL MARGINS cONVEX, SUbPARALLEL, WItH bROADLy ROUNDED DIStOLAtERAL ANGLES IN M. lucida sp. nov.).

BASED ON PHOtOGRAPHS OF tHE tyPE SPEcIMENS OF Portunus ponticus FAbRIcIUS, 1798 (JENSEN 2006), ItS AFFILIAtION tO tHE GENUS Monomia (E.G. NG et al. 2008) MAy NEED tO bE REVISED. THE REMAINING FOUR SPEcIES, M. argentata , M. gladiator (FAbRIcIUS, 1798), M. pseudoargentata (StEPHENSON, 1961), AND M. samoensis (WARD, 1939) , SEEM tO bE cLOSELy RELAtED tO M. lucida sp. nov. THE G1 OF M. pseudoargentata AND M. gladiator ARE ALSO SLENDER bUt LONGER, LESS cURVED, AND tHE cUtIcLE OF tHEIR bODy LAckS tHE IRIDEScENcE tyPIcAL FOR M. lucida sp. nov., AND M. argentata (SEE DAI & YANG 1991).

A SUItE OF cHARActERS DIStINGUISHES M. argentata FROM M. lucida sp. nov.: (1) SHARP SPINIFORM ANtEROLAtERAL tEEtH OF tHE cARAPAcE (KOcH et al. 2017: FIG. 7A), versus bEING StOUt AND FORWARD DIREctED IN tHE NEW SPEcIES ( FIGS 1 , 2A ); (2) tHE MALE PLEON WItH LAtERAL MARGINS OF tHE SIXtH PLEOMERE cONVEX, ANtERIORLy cONVERGENt (KOcH et al. 2017: FIG. 7B), versus SUbPARALLEL MARGINS WItH ROUNDED DIStAL SHOULDERS MEEtING tHE MUcH NARROWER tELSON ( FIG. 2B ); (3) FEMALE PLEON WItH A SHORt, GLAbROUS tRANSVERSE RIDGE ON PLEOMERE 4 ONLy (KOcH et al. 2017: FIG. 8E), versus A LONG tRANSVERSE RIDGE ON bOtH PLEOMERES 4 AND 5 ( FIG. 3C ); (4) RELAtIVELy NARROW cHELA, A LONG DIStODORSAL SPINE ON tHE cARPUS (KOcH et al. 2017: FIG. 7D), versus RELAtIVELy StOUt cHELA AND A REDUcED SPINE ( FIG. 2D ); (5) StOUt G1 WItH A bLUNt APEX (KOcH et al. 2017: FIG. 4 ), versus LONG, SLENDER, REctANGULAR cURVED G1 WItH A NON-EXPANDED APEX ( FIG. 3A ); (6) A DARk SPOt WItH DIFFUSED MARGIN ON tHE SWIMMING DActyLUS (KOcH et al. 2017: FIG. 5 ), versus A WELL- DEFINED, ROUNDED, WHItE OUtLINED DARk SPOt IN tHE NEW SPEcIES ( FIG. 1 ).

THE ActUAL RANGE OF M. lucida sp. nov. IS UNcLEAR, AS PREVIOUS REPORtS OF M. argentata MIGHt ALSO cOVER tHE PRESENt NEW SPEcIES. ONLy SOME OF tHE PREVIOUS DEScRIPtIONS PROVIDE DEtAILS ON tHE SHAPE OF tHE MALE PLEON AND GONOPODS (BARNARD 1950; EDMONDSON 1954; CROSNIER 1962; StEPHENSON & REES 1967A, b), OR tHE cOLOUR PAttERN (CHERtOPRUD et al. 2012), ALLOWING tHEM tO bE cOMPARED WItH tHE PRESENt NEW SPEcIES. StEPHENSON & REES (1967b: FIG 2A, E ) ILLUStRAtED tHE G1 OF ‘ M. argentata ’ FROM WEStERN INDIA, AND CHERtOPRUD et al. (2012) REPORtED ON LARGER bODIED SPEcIMENS OF ‘ M. argentata ’ FROM VIEtNAM (UP tO CW 46 MM), AND PROVIDED A cOLOUR PHOtOGRAPH (CHERtOPRUD et al. 2012: PL. 51F), WHIcH ALL cLEARLy IDENtIFy At LEASt SOME tHEIR SPEcIMENS AS bELONGING tO tHE PRESENt NEW SPEcIES. THUS, FOR NOW tHE kNOWN RANGE OF M. lucida sp. nov. IS LIMItED tO VIEtNAM (SOUtH CHINA SEA) AND NORtH-WEStERN INDIA (ARAbIAN SEA).

THE SyStEMAtIc StAtUS OF ANOtHER SPEcIES, M. samoensis (WARD, 1939) , IS UNcLEAR AS It WAS DEScRIbED FROM A SINGLE SMALL jUVENILE MALE ( FIG. 5 ) FROM SAMOA. OUR RE-EXAMINAtION OF tHE HOLOtyPE (AMNH 7482; 8.5 X 15 MM OF tHE cARAPAcE SIzE) HAS REVEALED tHAt tHE PLEON OF M. samoensis IS SUbtRIANGULAR, tAPERING DIStALLy. THE SPEcIMEN HAS UNDEVELOPED GONOPODS, bUt tHE FUSED PLEOMERES 3–5 cONFIRM It IS A MALE. THE DIStRIbUtION OF PAtcHES OF GRANULES DORSALLy ON tHE cARAPAcE DIFFERS FROM tHAt DEScRIbED HERE FOR M. lucida sp. nov., AND tHE ANtEROLAtERAL MARGIN IS PROPORtIONALLy DIStINctLy LONGER. THE DARk SPOt ON tHE LASt SEGMENt OF tHE SWIMMING LEG IS LARGE AND NOt cIRcULAR, AS IS ALSO EVIDENt FROM tHE ORIGINAL PHOtOGRAPHS OF M. samoensis PROVIDED by WARD (1939: FIGS. 5 , 6). THE EXtERNAL MORPHOLOGy OF tHE PRESERVED HOLOtyPE ARE SHOWN AGAIN HERE (FIG. 7A, B). ItS SPEcIFIc StAtUS MIGHt bE REVISED IN tHE FUtURE bASED ON FRESHLy cOLLEctED tOPOtyPIc SPEcIMENS.

ALcOck (1899) MENtIONED A VARIEty ‘ Neptunus argentatus VAR. glareosus ’ FROM tHE ANDAMAN ISLANDS tHAt MIGHt ALSO bELONG tO tHE M. argentata SPEcIES cOMPLEX. AccORDING tO tHE DEScRIPtION by ALcOck (1899), SPEcIMENS OF tHIS tAXON ARE cOMPLEtELy WItHOUt tOMENtUM ON tHEIR cARAPAcE, WHILE tHE cARAPAcE DORSUM AND PLEON OF M. argentata , s. str., AND M. lucida sp. nov., ARE DENSELy cOVERED by FINE PILA. THE FORMER SPEcIMENS ALSO POSSESS A HIGH tHIN cRESt ON PLEONAL SEGMENt 3, REPORtED AS bEING “tWIcE AS PROMINENt AS IS IN tHE tyPIcAL FORM” (ALcOck 1899: 37). THE PLEONAL cRESt IN tHE PRESENt NEW SPEcIES IS SIMILAR tO tHAt OF M. argentata , AND tHUS DIFFERENt FROM ALcOck’S SPEcIMENS.

SEqUENcES OF tHE 16S RRNA MItOcHONDRIAL MARkER OF FOUR SPEcIES OF tHE GENUS Monomia WERE ANALySED tO HIGHLIGHt tHEIR GENEtIc RELAtIONSHIPS, WItH Lupocycloporus gracilimanus AND Xiphonectes pulchricristatus AS OUtGROUPS ( FIG. 4 ). ALL FOUR ANALySED SPEcIMENS OF tHE NEW SPEcIES ARE NEStED tOGEtHER, WItH SPEcIMENS OF M. argentata SItUAtED AS A SEPARAtE, WELL-SUPPORtED SIStER LINEAGE. THE SPEcIMENS OF M. pseudoargentata AND M. gladiator REPRESENt A PAIR OF cLOSELy RELAtED tAXA cREAtING A SIStER bRANcH tO tHE AbOVE cOMbINED cLADE OF M. lucida sp. nov. AND M. argentata .

Distribution. NHAtRANG BAy, VIEtNAM—tHE tyPE LOcALIty. A PREVIOUS REPORt FROM tHE SAME LOcALIty: CHERtOPRUD et al. (2012) AS ‘ M. argentata ’ (IN PARt—SEE REMARkS). WItH cERtAINty, tHE NEW SPEcIES HAS ALSO bEEN REcORDED FROM NORtH-WEStERN INDIA (SEE StEPHENSON & REES 1967b, AS ‘ P. argentatus ’, IN PARt—SEE REMARkS).

Figures

FIGURE 1. Monomia lucida sp. nov., HAbiTuS ANd cOlOur PATTerN Of freSHly cOllecTed femAle PArATyPe CW 45.2 mm (NHMUK 2017.401). ScAle bArS:10 mm.

FIGURE 2. Monomia lucida sp. nov., mAle HOlOTyPe, CW 58.0 mm (MNHN-IU-2014-10082). A, dOrSum Of cArAPAce. B, PleON.C, lefT THird mAxilliPed.D, rigHT cHelA,OuTer vieW.ScAle bArS:A, D—10 mm, B, C—5 mm.

FIGURE 3. Monomia lucida sp. nov., SecONdAry SexuAl cHArAcTerS.MAle PArATyPe CW 42.5 mm (NHMUK 2017.402): A, lefT G1, veNTrAl vieW,TOTAl.B, APexOf G1. FemAle AllOTyPeCW 50.5 mm (MNHN-IU-2014-10083): C, PleON,veNTrAl vieW.D, rigHT vulvA, veNTrAl vieW.ScAle bArS:A—1 mm, B—0.1 mm, C—5 mm, D—2mm.

FIGURE 5. Monomia samoensis (WArd, 1939), HOlOTyPe, juveNile mAle CW 15 mm (AMNH 7482). A, OverAll HAbiTuS Of PreServedSPecimeN, dOrSAl.B, PleON.ScAle bAr:5 mm.

FIGURE4. COmbiNed BI/ML Tree WiTH cOmPArATive mATeriAl OfTHree Monomia SPecieS.Tree ObTAiNed by BAyeSiANANAlySiS Of 16S geNe SequeNceS uSiNg beST fiTTiNg HKY+G SubSTiTuTiON mOdel. SuPPOrT vAlueS fOr NOdeS exPreSSed AS PerceNTAgeS fOr BI ANd ML TreeS (TAmurA 3-PArAmeTerS mOdel + G), reSPecTively (BI/ML).