Metalycaeus ibex, 2017

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 : 84

Metalycaeus (?) ibex Páll-Gergely & Hunyadi n. sp.

FIGUrE 55E .

Type material. HOLOTypE MNHN IM- 2012-27042, VIETNam, TONkIN, Cam DUONG, LEG. MEssaGEr.

Etymology. THE prOmINENT rIbs Of THE R1 Of THIs NEw spECIEs rEsEmbLEs TO THE rIbbEd HOrNs Of THE ALpINE IbEx ( Capra ibex ).

Diagnosis. A smaLL spECIEs wITH vEry sHOrT R2 aNd R3, R3 wITHOUT swELLING; R1 wITH wIdELy-spaCEd, sTrONG rIbs, bOdy wHOrL kEELEd; pErIsTOmE rOUNdEd.

Description. SHELL ( FIGUrE 55E ) OUTLINE rOUNdEd frOm dOrsaL vIEw, spIrE raTHEr fLaT, wITH CONspICUOUsLy INfLaTEd R2, EdGE Of R1 sLIGHTLy, THaT Of R2 sHarpLy kEELEd; ONLy a sINGLE, sLIGHTLy wEaTHErEd sHELL was avaILabLE, THErEfOrE sCULpTUrE Of prOTOCONCH COULd NOT bE ExamINEd; IT CONsIsTs Of sLIGHTLy mOrE THaN 1.25 wHOrLs; R1 CONsIsTs Of 1.75 wHOrLs, raTHEr rEGULarLy rIbbEd, rIbs vEry wIdELy spaCEd aNd sHarp, wITH sOmE addITIONaL, INCOmpLETE rIbLETs bETwEEN maIN rIbs; spIraL sTrUCTUrE vIsIbLE ON sOmE, NOT sTrONGLy wEaTHErEd parTs Of R1 (INsIdE UmbILICUs aNd ON pENULTImaTE wHOrL faCING TO R3); rIbs bECOmING sLIGHTLy mOrE wIdELy-spaCEd TOwards ENd Of R1; TraNsITION bETwEEN R1 aNd R2 vEry CLEarLy vIsIbLE; R2 vEry dENsELy rIbbEd; CrOss sECTION Of rIbs COULd NOT bE ExamINEd; COmbINEd LENGTH Of R2 aNd R3 sHOrT, apprOxImaTELy 70–80 dEGrEEs ONLy; R3 sLIGHTLy sHOrTEr THaN R2; TraNsITION bETwEEN R2 aNd R3 rELaTIvELy CLEarLy vIsIbLE dUE TO absENCE Of rIbs ON R3 aNd vEry dEEp CONsTrICTION; R3 sEEms TO bE mUCH NarrOwEr THaN R2 bECaUsE Of dOrsaLLy vIsIbLE kEEL Of THE R2; R3 sEEmsINGLy smOOTH; apErTUrE sLIGHTLy TEardrOpsHapEd, NOT CrENULaTEd; INNEr LIp dOmINaNT, vEry THICk, OUTEr LIp sLImmEr, sOmEwHaT ELEvaTEd aNd sHarp aNd vEry sLIGHTLy rEfLECTEd.

Measurements (in mm). D = 3.4, H = 2.0 (N = 1, HOLOTypE).

Operculum. UNkNOwN.

Variation in specimens. ONLy THE HOLOTypE Is kNOwN.

Differential diagnosis. Metalycaeus ibex n. sp. CaN bE EasILy dIsTINGUIsHEd frOm aLL CHINEsE aNd VIETNamEsE LOw-spIrEd ALyCaEIdaE by THE COmbINaTION Of vEry wIdELy spaCEd, sTrONG rIbs ON R1, THE sHarpLy kEELEd aNd dENsELy rIbbEd R2, aNd THE vEry sHOrT R3. KEELEd pOpULaTIONs Of Dicharax depressus HavE a sUpErfICIaLLy sImILar sCULpTUrE aNd aNGULaTEd sHELL. HOwEvEr, THE kEELEd parT Of Dicharax depressus Is rEsTrICTEd TO R1, wHErEas IN CasE Of M. ibex n. sp. R2 Is kEELEd. MOrEOvEr, THE rIbs ON R1 arE mUCH mOrE wIdELy-spaCEd THaN IN Dicharax depressus , aNd R3 Is sHOrTEr IN M. ibex n. sp. SEE aLsO UNdEr M. awalycaeoides n. sp.

Distribution. THE ONLy kNOwN sHELL Of THE NEw spECIEs was COLLECTEd frOm Cam DUONG (= Cam ÐUòNG, N VIETNam, 22°25'N, 104°00'E, sEE SCHILEykO 2011).

Remarks. THE fINE sCULpTUrE Of THE prOTOCONCH aNd R2 Is UNkNOwN bECaUsE Of THE wEaTHErEd sTaTE Of THE HOLOTypE. Metalycaeus ibex n. sp. Is pLaCEd IN THE GENUs Metalycaeus bECaUsE Of THE spIraL LINEs vIsIbLE ON R1.

Figures

FIGURE 55. Shells of Metalycaeus species. A – C. Metalycaeus rathouisianus (Heude, 1882). A. syntype (SMF 39243) of M. rathouisianus. B. syntype (MCZ 167209) of Alycaeus dolomiticus Heude, 1890. C. MCZ 167222, labelled as Alycaeus neglectus Heude, 1886. D. Metalycaeus sinensis (Heude, 1882) (lectotype, MCZ 167216). E. Metalycaeus (?) ibex Páll- Gergely & Hunyadi n. sp., (holotype, MNHN IM- 2012 - 27042). Scale represents 5 mm. All photos: B. Páll-Gergely.