Dicharax planorbulus ( 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 : 68

Dicharax planorbulus ( Heude, 1885)

FIGUrEs 21B–C , 42E–F , 44 .

Alycoeus planorbulus Heude, 1885: 96 , pl. 24, figs 2, 2a–c.

Alycaeus (Chamalycaeus) planorbulus — Kobelt & Möllendorff, 1897: 149. Alycaeus (Chamalycaeus) planorbulus — Kobelt, 1902: 361.

Types examined. 10 syNTypEs (MCZ 167136) Of A. planorbulus , CHINa, TCHEN-K'EOU. ACCOrdING TO JOHNsON (1973) paraTypEs arE aLsO prEsENT IN THE NMNH (INv. NUmbEr: 472342). THEsE wErE NOT ExamINEd by Us.

Diagnosis. A mEdIUm sIzEd spECIEs wITH TypICaL Dicharax - TypE rIbs ON R2, vEry sHOrT R2 aNd R3, rOUNdEd pErIsTOmE aNd a wrINkLEd mULTIspIraL LamELLa ON THE OUTEr sIdE Of THE OpErCULUm.

Description. SHELL ( FIGUrEs 21B–C ) yELLOwIsH IvOry; sHELL OUTLINE rOUNdEd Or sLIGHTLy OvaL frOm dOrsaL vIEw, spIrE raTHEr fLaT, EdGE Of bOdy wHOrL rOUNdEd; prOTOCONCH ( FIGUrEs 42E–F ) LOw, CONsIsTING Of 1.25–1.5 wHOrLs (N = 3), raTHEr maTTE; R1 CONsIsTs Of 1.75 wHOrLs, rEGULarLy, dENsELy rIbbEd, rIbs LOw; rIbs bECOmING sLIGHTLy mOrE wIdELy-spaCEd TOwards ENd Of R1; TraNsITION bETwEEN R1 aNd R2 raTHEr smOOTH; R2 vEry dENsELy rIbbEd, rIbs CUrvEd TOwards apErTUrE; CrOss-sECTIONaL vIEw Of R2 COULd NOT bE ExamINEd, bUT IT Is prObabLy sImILar TO THOsE Of THE OTHEr spECIEs HavING CUrvEd rIbs; COmbINEd LENGTH Of R2 aNd R3 sHOrT, apprOxImaTELy 75–80 dEGrEEs; R2 aNd R3 Of abOUT THE samE LENGTH; TraNsITION bETwEEN R2 aNd R3 raTHEr CLEarLy vIsIbLE, INdICaTEd by a CONsTrICTION; R3 wITH a vEry sLIGHTLy ELEvaTEd swELLING sITUaTEd vEry CLOsE TO pErIsTOmE; R3 IrrEGULarLy, dENsELy rIbbEd, rIbs NOT CONspICUOUs; apErTUrE aLmOsT ExaCTLy rOUNdEd, wITHOUT kNOTs Or CONspICUOUs UppEr INCIsION; bOUNdary bETwEEN LIps sOmETImEs HardLy vIsIbLE, INNEr LIp vEry wEak, OUTEr LIp sOmEwHaT sHarp, bUT aLsO NOT CONspICUOUs.

Measurements (in mm). D = 4.1–4.8, H = 2.3–2.8 (N = 6, TypE sampLE).

Operculum. THE OUTEr sUrfaCE Of THE OpErCULUm (ExCEpT fOr THE NUCLEUs) Is COvErEd by aN ELEvaTEd, wrINkLEd LamELLa Of apprOxImaTELy sEvEN wHOrLs ( FIGUrEs 44A–D ). THE LamELLa Is bENT IN THE dIrECTION Of THE NUCLEUs, THErEfOrE IT bENT OvEr THE prEvIOUs wHOrLs Of ITsELf, bUT THE EdGEs Of THE dIffErENT wHOrLs Of THE LamELLa arE aLways CLEarLy vIsIbLE. THE OvEraLL sUrfaCE Of THE LamELLa fOrms a sHaLLOw fUNNEL.

Variation in specimens. THE TypE sampLE Is THE ONLy kNOwN maTErIaL. THEsE spECImENs sHOw ONLy sLIGHT varIabILITy IN TErms Of sHELL sIzE.

Differential diagnosis. THE ONLy sImILar CHINEsE spECIEs Is Dicharax bison n. sp. FOr dIffErENCEs, sEE THErE. THE sImILar, INdIaN D. rechilaensis Has mUCH LEss dENsE rIbs ON R2 aNd Has a mOrE CONspICUOUs swELLING ON R3.

Distribution. Dicharax planorbulus Is kNOwN frOm THE TypE LOCaLITy ONLy ( FIGUrE 7 ).

Figures

FIGURE 7. Distribution of narrow range or single-site endemic Dicharax species. Filled circle. Dicharax tangmaiensis (Chen & Zhang, 2001). Filled triangle, top up. Dicharax (?) alticola Páll-Gergely & Hunyadi n. sp. Filled diamond. Dicharax (?) immaculatus Páll-Gergely n. sp. Empty diamond. Dicharax microcostatus Páll-Gergely n. sp., Dicharax micropolitus Páll- Gergely & Hunyadi, n. sp. and Dicharax bison Páll-Gergely & Hunyadi n. sp. Filled triangle, top down. Dicharax robustus Páll-Gergely & Hunyadi, n. sp. Empty triangle, top down. Dicharax draco Páll-Gergely & Hunyadi n. sp. Empty square. Dicharax imitator Páll-Gergely & Hunyadi n. sp. Empty triangle, top up. Dicharax (?) moellendorffi (Kobelt & Möllendorff, 1886). Filled square. Dicharax (?) ellipticus n. sp. Cross. Dicharax (?) abdoui Páll-Gergely n. sp. Empty circle shows the position of Tchen K’eou (Chengkou), which is the type locality of Alycaeus pentagonus Heude, 1886 (synonym of Alycaeus anthostoma Möllendorff, 1885), Dicharax diminutus (Heude, 1885), Dicharax (?) fargesianus (Heude, 1885), Dicharax planorbulus (Heude, 1885), Metalycaeus muciferus (Heude, 1885), Alycaeus dolomiticus Heude, 1890 (synonym of Alycaeus rathouisianus Heude, 1882), Dicharax (?) dolichodeiros (Heude, 1890), Metalycaeus (?) elevatus (Heude, 1886), Metalycaeus (?) expansus (Heude, 1890).

FIGURE 21. Shells of Dicharax species. A. Dicharax bison Páll-Gergely & Hunyadi n. sp. (holotype, HNHM 99703). B – C. Dicharax planorbulus (Heude, 1885) (syntypes, MCZ 167136). Scale represents 5 mm. All photos: B. Páll-Gergely. Scale represents 5 mm.

FIGURE 42. Protoconchs of Dicharax species. A – B. Dicharax imitator Páll-Gergely & Hunyadi n. sp. (holotype, HNHM 99706). C – D. Dicharax micropolitus Páll-Gergely & Hunyadi, n. sp. (holotype, HNHM 99709). E – F. Dicharax planorbulus (Heude, 1885) (syntype, MCZ 167136). All images: B. Páll-Gergely.

FIGURE 44. Outer side of the operculum of Dicharax planorbulus (Heude, 1885) (syntype, MCZ 167136). All images: B. Páll-Gergely.