Dicharax diminutus ( Heude, 1885 )

Asami, Takahiro, 2017, Revision of the Alycaeidae of China, Laos and Vietnam (Gastropoda: Cyclophoroidea) I: The genera Dicharax and Metalycaeus, Zootaxa 4331 (1), pp. 1-124 : 50-52

Dicharax diminutus ( Heude, 1885)

FIGUrE 33A–C .

Alycoeus diminutus Heude, 1885: 96 , pl. 24, figs 5, 5a.

Alycaeus diminutus — Heude, 1886: 210.

Alycaeus (Orthalycaeus) diminutus — Möllendorff, 1886: 170. Alycaeus (Orthalycaeus) nanus Möllendorff, 1886: 170 , pl. 5, fig. 8, new synonym. Alycaeus (Chamalycaeus) diminutus — Kobelt & Möllendorff, 1897: 148. Alycaeus (Chamalycaeus) nanus — Kobelt & Möllendorff, 1897: 149. Alycaeus (Chamalycaeus) diminutus — Kobelt, 1902: 354.

Alycaeus (Chamalycaeus) nanus — Kobelt, 1902: 359.

Chamalycaeus nanus — Yen, 1939: 29, pl. 2, fig. 31.

Types examined. LECTOTypE ( SMF 39246) aNd 5 paraLECTOTypEs ( SMF 39247 ) Of Alycaeus (Orthalycaeus) nanus , KwEI-yaNG-dsHOU, HUNaN: CHINa , COLL. MöLLENdOrff; SMF 39248/3 paraLECTOTypEs, samE daTa as prEvIOUs, COLL. O. BOETTGEr. NO TypE spECImEN Of Alycoeus diminutus wErE rEpOrTEd by TO JOHNsON (1973). SEE aLsO REmarks.

Museum material examined. SMF 39255/1 (LabELLEd as A. minutus ), HUNaN, CHINa , COLL. MöLLENdOrff Ex COLL. HEUdE; NHMUK 1891.3.17.783–785/3, HUNaN, LEG. HUNGErfOrd ; NHMUK 20150475 /2, CHINa, HUNaN , COLL. W. BLaNfOrd; NHMUK 20150476 /3, HUNaN, V.W. MaCANdrEw COLL. ; NHMUK 20150477 /3, HUpé, CHINa, E.R. SykEs COLL. 1954 ; NHMUK 20150478 /1, HUNaN, CHINa, E.R. SykEs COLL. 1954.

New material examined. 2 OK/1, OKA /2, PGB/2 (Ex COLL. K. OHara), 0060109A CHINa, YUNNaN, WENsHaNzHUaNG ZUmIaOzU ZIzHIzHO, GUaNGNaN XIaN, LIjI, 1611 m, 23°45.54175'N, 104°59.55567'E, LEG. K. OHara, K. OkUbO & J.U. OTaNI, 0 9 JaN 2006.

Diagnosis. A smaLL TO vEry smaLL spECIEs wITH TypICaL Dicharax - TypE rIbs ON R2, bLUNT swELLING ON R3 aNd rOUNdEd apErTUrE.

Description of the type series. SHELL yELLOwIsH IvOry; sHELL OUTLINE OvaL frOm dOrsaL vIEw, sHELL aLmOsT fLaT, EdGE Of bOdy wHOrL Is rOUNdEd; prOTOCONCH LOw, CONsIsTING Of 1.5 wHOrLs, raTHEr maTTE; R1 CONsIsTs Of 1.5 Or sLIGHTLy mOrE wHOrLs, rEGULarLy, dENsELy rIbbEd; TraNsITION bETwEEN R1 aNd R2 HardLy vIsIbLE; R2 sLIGHTLy mOrE dENsELy rIbbEd THaN R1; CrOss-sECTIONaL vIEw Of R2 COULd NOT bE ExamINEd, bUT prObabLy sImILar TO THOsE Of THE OTHEr spECIEs HavING CUrvEd rIbs; LENGTH Of R2 aNd R3 sLIGHTLy mOrE THaN a qUarTEr wHOrL COmbINEd; R2 aNd R3 Of abOUT THE samE LENGTH; TraNsITION bETwEEN R2 aNd R3 CLEarLy vIsIbLE, INdICaTEd by sLIGHT CONsTrICTION; R3 wITH raTHEr IrrEGULar GrOwTH rIbs, rIb dENsITy sImILar TO THaT Of R1; apErTUrE rOUNdEd; OUTEr LIp sLIGHTLy rEfLECTEd, sHarp; INNEr LIp THICkENEd.

Measurements (in mm). D = 2.8–3.3, H = 1.6–1.9 (N = 5, spECImENs frOm dIffErENT sampLEs).

Operculum. THE INNEr sUrfaCE COULd NOT bE ExamINEd, THE OUTEr sUrfaCE Is NEarLy smOOTH, bUT THE mULTIspIraL CHaraCTEr Is rECOGNIsabLE (ExamINEd: sampLE 20060109A, LECTOTypE Of nanus , syNTypE Of diminutus ).

Variation in specimens. THE spECImENs LIsTEd UNdEr THIs spECIEs sHOw LITTLE varIabILITy, aLTHOUGH THEy HavE bEEN COLLECTEd far frOm EaCH OTHEr. SEE aLsO rEmarks.

Differential diagnosis. THE ONLy NEwLy COLLECTEd sampLEs wE ExamINEd wErE COLLECTEd IN sOUTHEasT YUNNaN, wHErE IT Is sympaTrIC wITH a D. cristatus pOpULaTION (TypICaL simplicilabris -LIkE sHELLs). THE TwO spECIEs arE sImILar IN OvEraLL sHELL sHapE aNd THE prOpOrTIONs Of THE sHELL rEGIONs, bUT D. cristatus Is mUCH LarGEr, aNd Has a sLIGHTLy CrENULaTEd pErIsTOmE. SEE aLsO UNdEr Dicharax depressus aNd D. fargesianus aNd D. plicilabris .

Distribution. CHINa (CHONGqING, HUNaN aNd YUNNaN prOvINCEs). SEE aLsO REmarks aNd FIGUrE 14 .

Remarks. THErE Is a sampLE dEpOsITEd IN THE SENCkENbErG MUsEUm (SMF 39255) wITH THE fOLLOwING daTa ON MöLLENdOrff's TypICaL smaLL yELLOw LabEL: " Alycaeus nanus v. MLLdff/ ( minutus HEUdE) /xx / HUNaN ". THE TwO smaLL x-sIGNs INdICaTE THaT MöLLENdOrff rECEIvEd THE sHELL frOm THE aUTHOr (RONaLd JaNssEN, pErs. COmm.). THE spECIEs NamE Is NOT COrrECTLy wrITTEN (" minutus " INsTEad Of diminutus ) ON THE LabELs, aNd THE sHELLs arE CErTaINLy NOT TypE spECImENs, bECaUsE THEy wErE COLLECTEd frOm a sITE dIffErENT frOm THE TypE LOCaLITy. GIvEN THIs, THEy wErE IdENTIfIEd as Alycaeus diminutus by HEUdE. THEsE diminutus sHELLs arE IdENTICaL wITH MöLLENdOrff's nanus . THErEfOrE, wE prOvIsIONaLLy syNONymIzE THE LaTTEr wITH Alycaeus diminutus .

WE ExamINEd THE THrEE GrEaTLy wEaTHErEd sHELLs Of JaECkEL (OrIGINaL INv. NUmbEr: SMF 20 1255), wHICH wErE pUbLIsHEd UNdEr THE NamE Chamalycaeus nanus (sEE JaECkEL 1950). ONE Of THEm Is Metalycaeus heudei , aNOTHEr was a Metalycaeus spECIEs (sEE UNdEr " Metalycaeus sp."), aNd THE THIrd, prObabLy Dicharax spECIEs COULd NOT bE IdENTIfIEd dUE TO THE ExTrEmELy wEaTHErEd sTaTE Of THE sHELL. THUs THE ONLy rECOrd Of D. nanus frOm VIETNam prOvEs TO bE ErrONEOUs aNd sHOULd bE dELETEd frOm THE VIETNamEsE faUNa LIsT.

THE TypE spECImENs Of Alycaeus diminutus frOm CHENGkOU, Alycaeus nanus frOm KwEI-yaNG-dsHOU, aNd THE sampLE 20060109A frOm sOUTHEasT YUNNaN arE NEarLy IdENTICaL IN TErms Of sHELL CHaraCTErs ( FIGUrEs 33A–C ). THE dIsTaNCE bETwEEN THEsE THrEE sITEs Is apprOxImaTELy 750–950 km, wITHOUT kNOwN pOpULaTIONs Of sImILar spECImENs IN bETwEEN. SEE CONCLUdING REmarks.

Figures

FIGURE 14. Distribution of Dicharax species. Empty circle. Dicharax (?) dolichodeiros (Heude, 1890). Triangle. Dicharax diminutus (Heude, 1885) (1. Tchen k'eou: type locality of Alycoeus diminutus. 2. Kwei-yang-dshou, type locality of Alycaeus nanus. 3. 20060109 A). Filled circle. " Dicharax sp. " (4. 2009 / 105 = D. cf. abdoui n. sp.. 5. 2011 / 20 = D. cf. abdoui n. sp.. 6. Pac Kha).

FIGURE 33. Shells of Dicharax species. A – C. Dicharax diminutus (Heude, 1885). A. SMF 39255. B. Dicharax diminutus (lectotype of A. nanus Möllendorff, 1886, SMF 39246). C. 20060109 A, coll. PGB. D. Dicharax plicilabris (Möllendorff, 1886). Scale represents 5 mm. All photos: B. Páll-Gergely.