Exiligada pallida, 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 : 708

EXILIGADA PALLIDA SP. NOV.

( FIGS 4B , 6C , 20A–C , 21 )

Holotype: AUSTRALIA, NT, VRD, 28.2 km east of Spring Creek Station H /S, base of limestone cliffs along a seasonal stream bed, 15–20 m or more high, large overhangs, talus and boulders, under rocks, 17°00 ′ 44 ′′ S, 129°07 ′ 35 ′′ E (coll. V. Kessner, R. Hokkanen, 30.viii.2009; WA-66 /09) ( WAM S83174 ).

Paratypes: AUSTRALIA, NT, VRD , same data as for holotype, 22 wet ( WAM S49215), 106 dry ( WAM S49150 ) .

Etymology: In reference to the pale shell background colour, derived from ‘pallidus’ (Latin = pale); adjective of feminine gender.

Genitalia ( Fig. 19 ). Epiphallus length two thirds that of penis. Vas deferens entering penial sheath from one third up. Penis seven times longer than wide, coiled inside sheath, with posterior part of inner wall supporting three regularly nodulose, longitudinal pilasters fading into three irregularly shaped folds not reaching the genital pore. Vagina as long as penis, two times longer than free oviduct, bursa copulatrix with long, rounded well-differentiated end.

Remarks: Together with E. qualis narrowest umbilicus of genus. Shell colour pattern very similar to shells of four congeners; to be distinguished from E. longicauda by larger number of spiral bands, from E. negriensis by more regularly interrupted bands, from E. pallida by darker background, and from E. punctata by absence of maculations. Along with E. longicauda , only species in genus with a coiled penis. Penis length relative to width (pl/pw) larger than average and smaller than E. longicauda ; epiphallus length relative to penis (el/pl) smaller than average and two times that of E. longicauda . Inner penial wall sculpture unique, in consisting of longitudinal pilasters sculptured by regularly spaced and shaped nodules. Vagina length relative to penis (vl/pl) larger than average and almost as large as in E. longicauda ; vagina length relative to free oviduct (vl/ol) Description: Shell ( Figs 4B , 6C , 20A–C ). Large, moderately elevated, moderately thick; micropustulations present. Shell background colour pale horn fading to whitish towards shell base, with several conspicuous to faint brown-reddish spiral bands, equally conspicuous on entire shell, often present on shell base, often regularly interrupted radially and giving the appearance of a regular radial bandage; maculations absent.

Genitalia ( Fig. 21 ). Epiphallus as long as penis. Vas deferens entering penial sheath from halfway up. Penis six times longer than wide, not coiled inside sheath, with inner wall supporting a posterior coneshaped pad and five longitudinal pilasters, two arising close to posterior part of pad and reaching genital pore, three from posterior end of penis, only two of which reaching genital pore. Vagina one third shorter than penis length and as long as free oviduct, bursa copulatrix with long, pointed well-differentiated end.

Remarks: Teleoconch microsculpture differing from that of E. negriensis by presence of micropustulations.

Shell colour pattern similar to that of four other Exiligada species ; to be distinguished from E. longicauda and E. nodulicauda by its lighter background colour and from E. punctata by absence of maculations.

Penis length relative to width (pl/pw) average and larger than in sister species E. negriensis ; epiphallus length relative to penis (el/pl) as long as average and as E. negriensis . Inner penial wall sculpture similar to E. negriensis and E. punctata , to be distinguished from these species by narrower posterior pad and longer longitudinal pilasters, always reaching the posterior part of the wall, and by noncorrugated posterior pad. Vagina length relative to penis (vl/pl) and relative to free oviduct (vl/ol) average.

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 19. Penial anatomy of E. nodulicauda sp. nov. (holotype WAM S83173). Scale bar = 5 mm.

Figure 20. SEM micrographs of Exiligada shells.A-C, E. pallida sp. nov. (paratype WAM S49150). 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. punctata sp. nov. (paratype WAMS49139). 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 21. Penial anatomy of E. pallida sp. nov. (holotype WAM S83174). Scale bar = 5 mm.