Exiligada rivifontis, Criscione & Law & Köhler, 2012

Criscione, Francesco, Law, Margot Louisa & Köhler, Frank, 2012, Land snail diversity in the monsoon tropics of Northern Australia: revision of the genus Exiligada Iredale, 1939 (Mollusca: Pulmonata: Camaenidae), with description of 13 new species, Zoological Journal of the Linnean Society (Zool. J. Linn. Soc.) 166 (4), pp. 689-722 : 712-713

EXILIGADA RIVIFONTIS SP. NOV.

( FIGS 4I , 6F , 23D–E , 25 )

Holotype: AUSTRALIA, NT, VRD, 30.4 km east-southeast of Spring Creek Station H /S, limestone gully along a stream, cliffs 8–10 m high, base of limestone cliffs along a seasonal stream, talus, spinifex and native grass, in talus. 17°02 ′ 04 ′′ S, 129°08 ′ 35 ′′ E (coll. V. Kessner, R. Hokkanen, 30.viii.2009; WA-67 /09) ( WAM S83176).

(17°04 ′ 32 ′′ S, 129°00 ′ 10 ′′ E). The species is removed from the synonymy of E. negriensis . Together with E. nodulicauda it has the narrowest umbilicus in the genus. Teleoconch microsculpture is unique in being composed of regularly arranged microdepressions rather than micropustulations. Shell colour pattern not easily distinguished from E. brabyi . Penis length Paratypes: Same data as for holotype, four wet (WAM S49224 ).

Other material: AUSTRALIA, NT, VRD , 28.2 km east of Spring Creek Station H/S, base of limestone cliffs 15–20 m or higher, large overhangs, in talus and under boulders, 17°00 ′ 44 ′′ S, 129°07 ′ 35 ′′ E (coll. V. Kessner, R. Hokkanen, 30.viii.2009; WA-66 /09), three wet ( WAM S49225 ); 30.4 km east-south-east of Spring Creek Station H/S, limestone gully along a stream, cliffs 8–10 m high, base of limestone cliffs along a seasonal stream, spinifex and native grass, in talus, 17°02 ′ 04 ′′ S, 129°08 ′ 35 ′′ E (coll. V. Kessner, R. Hokkanen, 30.viii.2009; WA-67 /09), three dry ( WAM S94141 ) ; AUSTRALIA, WA, EK , 1.7 km south of Behn River crossing, limestone ridge west of Duncan Hwy , east large open limestone ridge, very small vine thicket patches, dead in rock piles, 16°35 ′ 48 ′′ S, 128°57 ′ 10 ′′ E (coll. V. Kessner, R. Hokkanen, 27.viii.2009; WA-54 /09), five dry ( WAM S49140 ); 12.3 km east of Spring Creek Station H /S, low exposed hills with small 2–3-m-high limestone cliffs east of Duncan Hwy , spinifex, few fig trees, dead under talus, 16°59 ′ 57 ′′ S, 128°58 ′ 34 ′′ E (coll. V. Kessner, R. Hokkanen, 30.viii.2009; WA-70 /09), one dry ( WAM S49142 ); Halls Creek District, 57 km east of Nicholson Station H /S, very open limestone area, well-developed spinifex, talus under spinifex, 17°58 ′ 43 ′′ S, 128°21 ′ 34 ′′ E (coll. V. Kessner, R. Hokkanen 1.ix.2009; WA-75 /09), two dry ( WAM S49143 ) .

Etymology: In reference to Spring Creek, close to type locality, Latinized and derived from ‘rivus’ (Latin = creek) and ‘fons’ (Latin = spring), nouns of respectively masculine and feminine gender in genitive case.

Description: Shell ( Figs 4I , 6F , 23D, E ). Large, strongly elevated, moderately thin; micropustulations present. Shell background colour brown horn fading to whitish towards shell base, with one faint to conspicuous continuous narrow brown-reddish spiral band on whorl periphery; maculations absent.

Genitalia ( Fig. 25 ). Epiphallus two times longer than penis. Vas deferens entering penial sheath from one third up. Penis three times longer than wide, not coiled inside sheath, with inner wall supporting several moderately large, irregularly shaped longitudinal pilasters, often not running along entire wall length. Vagina two times shorter than penis and free oviduct, bursa copulatrix with short, rounded welldifferentiated end.

Remarks: Highest shell, largest shell diameter, and largest number of shell whorls (together with E. gregoriana and E. rivifontis ) within genus. Colour pattern very similar to E. calciphila , E. floraevallis , E. gregoriana , E. limbunya , and E. unistriata . Penis length relative to width (pl/pw) smaller than the average and E. rivifontis ; epiphallus length relative to penis (el/pl) 1.5 times the average and as large as in E. floraevallis . Penial inner wall sculpture very similar to E. floraevallis and not easily distinguishable. Vagina length relative to penis (vl/pl) average and as large as in E. floraevallis , vagina length relative to free oviduct (vl/ol) smaller than average and E. floraevallis .

Figures

Figure 4. Photographs of living specimens of Exiligada species (courtesy Vince Kessner, Adelaide River). A, E. negriensis Iredale, 1939. B, E. pallida sp. nov. C, E. nodulicaudata sp. nov. D, E. punctata sp. nov. E, E. qualis Iredale, 1939. F, E. monochroma sp. nov. G, E. unistriata sp. nov. H, E. floraevallis sp. nov. I, E. rivifontis sp. nov.

Figure 6. Shells of Exiligada species. A, E. montejinni sp. nov. (paratype AM C.469982). B, E. nodulicauda sp. nov. (paratype WAM S49160). C, E. pallida sp. nov. (paratype WAM S49215). D, E. punctata sp. nov. (paratype WAM S49221). E, E. qualis Iredale, 1939 (holotype AM C.64866). F, E. rivifontis sp. nov. (WAM S49225). G, E. unistriata sp. nov. (paratype AM C.470460). Scale bar = 2 mm. Note that foot produces from some shells.

Figure 23. SEM micrographs of Exiligada shells. A-C, E. qualis Iredale, 1939 (paratype AM C.64915). A, Apical view showing protoconch and first whorl. B, Close-up from above of sculpture across entire shell. C, Microsculpture on teleoconch whorl. D-F, E.rivifontis sp. nov. (WAM S49141). D, Apical view showing protoconch and first whorl. E, Close-up from above of sculpture across entire shell. F, Microsculpture on teleoconch whorl. Scale bars: A-B, D-E = 1 mm, C, F = 0.5 mm.

Figure 25. Penial anatomy of E. rivifontis sp. nov. (holotype WAM S83176). Scale bar = 5 mm.