Exiligada, IREDALE, 1939: 68

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 : 695-696

EXILIGADA IREDALE, 1939: 68 . SOLEM, 1984: 670

Generic diagnosis: Shell ( Figs 4–6 ): moderately large, subglobose, periphery slightly angulated to rounded, spire weakly to moderately elevated, thin to moderately thick; umbilicus narrowly winding, open to almost completely concealed by columellar reflection; protoconch and teleoconch with moderately fine radial growth lines, fine micropustulations or microdepressions sometimes present. Last whorl moderate to wide in cross-section, periphery uniformly rounded. Apertural lip reflected, moderately expanded, parietal wall thin; no internal lip nodes. Shell colour variable, background whitish, yellowish or brownish horn, without or with one to several moderately wide to thin brown-reddish spiral bands, sometimes randomly to regularly dashed, with or without dark grey punctuations.

Genitalia: typically camaenid with prostate and uterus being fused forming spermoviduct and lacking diverticulum and stimulatory organs; development of gonads depending on seasonal activity and maturity. Penial sheath well developed, extending entire length, usually thickened distally. Epiphallus forming a tube surrounded by thick layers of muscle, well separated from penis, distally connected to penis through a narrow duct in a zigzag configuration; epiphallus variable in length, three times shorter to two times longer than penis. Penial retractor muscle inserting on vas-epiphallic junction, with fibres continuing along epiphallus, and attached to apical part of penis. Vas deferens entering penial sheath basally to almost halfway up, continuing apically within sheath until reflexing into epiphallus. Penis ten to three times longer than wide, not coiled or coiled inside sheath, with moderately thick wall; inner penial wall structure variable, usually consisting of several irregularly shaped, often corrugated, wide longitudinal pilasters or of fewer regularly shaped, smooth, narrower ones. Pilaster often running along entire wall length, but sometimes interrupted. In some species finer sculptures, such as irregular tubercles or regular nodules, can be present. Sculptures of posterior part of wall often different from that of anterior part. Vagina four times shorter to slightly longer than penis, usually three times shorter to as long as free oviduct, but up to more than two times longer in some species; bursa copulatrix relatively simple, usually as long as free oviduct and sometimes slightly shorter, reaching anterior end of spermoviduct, with or without welldifferentiated end. Albumen gland large. Talon embedded in albumen gland within proximal portion. Hermaphroditic duct tightly undulating.

Aestivating strategy: Aestivating as ‘free sealers’.

Remarks: If not stated otherwise, holotypes are dissected wet specimens, whose shell was cracked to permit access to soft tissues. References to size are intended as relative to other congeneric species.

Typical combination of features separating Exiligada from other camaenids are shell shape of the ‘chloritid type’, presence of dashed shell bands (where present), and in particular shape and zigzag configuration of epiphallus. Amongst other camaenid genera occurring in EK and NT, Mesodontrachia is most similar in shell shape and size but differs by slightly lower spire and by whorls being never angulated as in some but not all Exiligada species ; shell very different from all other genera by larger size and much higher spire, narrower umbilicus with greater extent of cover by columellar reflection; protoconch microsculpture similar to Prototrachia and some Ordtrachia species ; teleoconch sculpture similar to Mesodontrachia but differing from remaining genera by absence of radial ribs and spiral keels; shell colour usually lighter; colour pattern very distinct from all other genera by presence of spiral bands, but species with no banding most similar to Mesodontrachia . Bursa copulatrix similar to that of Mesodontrachia and Ordtrachia but much shorter than in Torresitrachia ; penis differing from that of Mesodontrachia by presence of epiphallus; epiphallus differing from Torresitrachia in shape, thickness of wall, and by absence of flagellum; penial wall differing by presence of main stimulatory pilaster in some Exiligada species.

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 5. Shells of Exiligada species. A, E. negriensis (holotype AM C.64865). B, E. brabyi sp. nov. (paratype C.443279). C, E. calciphila sp. nov. (paratype C.462723). D, E. floraevallis sp. nov. (paratype WAM S49204). E, E. gregoriana sp. nov. (paratype AM C.462820). F, E. limbunya sp. nov. (paratype AM C.470205). G, E. longicauda sp. nov. (paratype WAM S49228). H, E. monochroma sp. nov. (paratype AM C.469772).

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.