Exiligada negriensis, IREDALE, 1939

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 : 696-700

EXILIGADA NEGRIENSIS IREDALE, 1939

( FIGS 4A , 5A , 7A–C , 8 )

Exiligada negriensis Iredale, 1939: 69 , plate V, figure 4.

Exiligada negriensis – Solem, 1984: 673–677, fig. 174 (a–c) (in part).

Material examined: AUSTRALIA, NT, VRD: holotype from 40 km north of Ord River Station , Negri outstation (coll. R. Helms, 1896), dry ( AM C.64865); ten paratypes (same data as for holotype) ( AM C.64916); 6 km south-west of Lissadell Station homestead (H/S), limestone outcrops with slabs on upper slopes, spinifex, patches of vine thicket, in talus, under boulders, 16°43 ′ 16 ′′ S, 128°31 ′ 23 ′′ E, (coll. V. Kessner, R. Hokkanen, 28.viii.2009; WA-57 /09) two wet ( WAM S49214 ) , 12 dry ( WAM S49145 ) ; 9.5 km south-east of Lissadell Station H/S, limestone ridge east of Ord River, dissected limestone area with small vine thicket patches on the slopes, exposed on the top, under talus, 16°43 ′ 07 ′′ S, 128°37 ′ 51 ′′ E (coll. V. Kessner, R. Hokkanen, 28.vii.2009; WA-58 /09), 18 dry ( WAM S49146 ) ; south-east of Lake Argyle , 15.5 km south-west of Behn River crossing, large limestone mass with karst formations, vine thicket patches, native grasses, under slabs, 16°37 ′ 20 ′′ S, 128°48 ′ 47 ′′ E (coll. V. Kessner, R. Hokkanen, 28.viii.2009; WA-59 / 09), 32 dry ( WAM S49147 ) ; 29.8 km north of Spring Creek Station H/S, East Kimberley limestone gully along a seasonal stream with vine thicket patches, under large slabs, 16°43 ′ 40 ′′ S, 128°52 ′ 25 ′′ E (coll. V. Kessner, R. Hokkanen, 28.viii.2009; WA-60 /09), 16 dry ( WAM S49148 ) ; 1 km south of Negri River junction, east bank of Ord River, narrow and open limestone ridge, very dry, dead in crevices, 17°04 ′ 38 ′′ S, 128°53 ′ 48 ′′ E (coll. V. Kessner, R. Hokkanen, 29.viii.2009; WA-65 /09), 13 dry ( WAM S49149 ) ; 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, talus, spinifex and native grass, 17°02 ′ 04 ′′ S, 129°08 ′ 35 ′′ E (coll. V. Kessner, R. Hokkanen, 30.viii.2009; WA-67 / 09) one wet ( WAM S83171) , 130 dry, two wet ( WAM S49151 ) ; 39.6 km south-east of Spring Creek Station H/S, low limestone cliffs over sandstone base south of Stirling Creek, spinifex and native grass, in talus, 17°11 ′ 20 ′′ S, 129°10 ′ 35 ′′ E (coll. V. Kessner, R. Hokkanen, 30.viii.2009; WA-68 /09), 1 wet, 53 dry ( WAM S49152 ) ; low exposed limestone hills in Nelson Creek drainage, Limbunya Station, limestone layer over sedimentary rocks, spinifex, in rock piles, under spinifex, 17°18 ′ 23 ′′ S, 129°12 ′ 29 ′′ E (coll. V. Kessner, R. Hokkanen, 30.viii.2009; WA-69 /09), eight wet ( WAM S49216 ) , 29 dry ( WAM S49153 ) ; 30.2 km north-east of Kirkimbie Station (Stn) H/S, karst limestone formation in open woodland, spinifex, 17°29 ′ 23 ′′ S, 129°22 ′ 46 ′′ E (coll. V. Kessner, R. Hokkanen, 2.ix.2009; WA-82 /09) one wet ( WAM S83172 ) ; 21.6 km north of Kirkimbie Station H/S, narrow limestone ridge, steep open slopes, well-developed spinifex on upper slopes, in talus, under spinifex, 17°32 ′ 20 ′′ S, 129°16 ′ 03 ′′ E (coll. V. Kessner, R. Hokkanen, 2.ix.2009; WA-83 /09), six wet ( WAM S49218) , 20 dry ( WAM S49161 ) ; west of Duncan Highway ( Hwy ), Spring Creek Station, limestone area east of Mud Spring Creek, open limestone slopes, well-developed spinifex, dead under slabs, 16°41 ′ 20 ′′ S, 128°54 ′ 55 ′′ E (coll. V. Kessner, R. Hokkanen, 3.ix.2009; WA-85 /09), one dry ( WAM S49162 ) ; 5.4 km south-west of Lissadell Stn H/S, low limestone ridge, base of the cliffs, small pockets of vine thicket, under rocks in loose soil, 16°42 ′ 31 ′′ S, 128°30 ′ 58 ′′ E (coll. V. Kessner, K. Carnes 6.ix.2009; WA-97 /09), two dry ( WAM S49166 ) ; 6.7 km south-west of Lissadell Stn H/S, narrow limestone ridge, base of the cliffs, small pockets of vine thicket, spinifex, under rocks, 16°43 ′ 17 ′′ S, 128°30 ′ 46 ′′ E (coll. V. Kessner, K. Carnes, 6.ix.2009; WA-98 /09), two dry ( WAM S49219 ) , nine dry ( WAM S49163 ) ; 12 km south-west of Lissadell Stn H/S, low limestone exposed hill with karst limestone, few shady trees, spinifex and tussock grass, in talus, 16°46 ′ 16 ′′ S, 128°30 ′ 09 ′′ E (coll. V. Kessner, K. Carnes, 6.ix.2009; WA-99 /09), 16 dry ( WAM S49164 ) .

Description: Shell ( Figs 4A , 5A , 7A–C ). Large, moderately elevated, moderately thick; micropustulations absent; background colour yellowish horn fading to whitish towards shell base, with several conspicuous to faint brown-reddish spiral bands, equally conspicuous on entire shell, often present on base, often interrupted radially; no maculations.

Genitalia ( Fig. 8 ). Epiphallus as long as penis. Vas deferens entering penial sheath halfway up. Penis five times longer than wide, not coiled inside sheath, inner penial wall with weak, irregular longitudinal pilasters restricted to anterior half, posteriorly with thick, cone-shaped pad. Vagina half as long as penis, a third of length of free oviduct, bursa copulatrix with elongated, pointed well-differentiated end.

Remarks: The species is delimited here differently as compared to the latest revision of Solem (1984). Originally, amongst a single set of mostly eroded shells from the same locality, Iredale (1939: 69) recognized two Exiligada species based on shell morphology and coloration: E. negriensis , which he designated as the type species of the genus Exiligada , and E. qualis . The type locality as originally cited by Iredale (1939) (‘Negri Outstation’) could not be specified subsequently ( Solem, 1984). However, based on the information provided by Iredale [25 miles (= 40 km) north of Ord River Station, near Negri River], the type locality is herein restricted to an area close to the Negri River between the point where the Negri River flows into the Ord River in WA (17°04 ′ 11 ′′ S, and E. brabyi both having shells with continuous spiral bands.

Exiligada negriensis differs from Exiligada pallida in absence of micropustulations on the shell. Its shell colour pattern is similar to that of four other Exiligada species , which are distinguished by a lower number of spiral bands ( E. longicauda ), by bands being more regularly interrupted ( E. nodulicauda ), by lighter background ( E. pallida ), and presence of maculations ( E. punctata ). Its penis length relative to width (pl/pw) is smaller than average, almost as large as in E. pallida ; epiphallus length relative to penis (el/pl) is average, as large as in E. pallida . Inner penial wall sculpture is very similar to E. pallida and E. punctata , differing by wider posterior pad and shorter longitudinal pilasters of the penial wall never extending to posterior part of wall. Vagina length relative to penis and free oviduct (vl/pl, vl/ol) is the smallest amongst congeners.

128°53 ′ 10 ′′ E) and the Duncan Highway bridge over the Negri River near the WA / NT border (17°04 ′ 32 ′′ S, 129°00 ′ 10 ′′ E). Solem (1984: 672–673) considered the differences between the type series of E. negriensis and E. qualis as not significant and synonymized the two species names. Based on comparative study of additional material, we found that the area including the type locality is inhabited by three Exiligada species. Differences between two of these species as delimited herein are consistent with the original delimitation of E. negriensis and E. qualis by Iredale (1939), refuting Solem’s (1984) proposal that both were identical (see also below under E. qualis ). To complicate matters even further, Solem (1984: 676) used specimens from ‘Duncan Hwy, 37.2 km N of Nicholson River’ (about 60–70 km south of the type locality) to describe the genital anatomy of what he considered to be E. negriensis . We studied material from sites much closer to the type locality and found that E. negriensis differs from Solem’s (1984: 676, fig. 175) anatomical description. Based on shell colour patterns, we found that he used specimens from a different species, named herein Exiligada brabyi further below, to illustrate the genital anatomy of E. negriensis . Hence, Solem’s (1984) description of ‘ E. negriensis ’ is based on mixed material from three species ( E. negriensis , E. qualis , E. brabyi ). His description and figure of genital features is here attributed to E. brabyi (see below). Exiligada negriensis as restricted here is defined by the presence of dashed spiral bands on shells as opposed to E. qualis

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 7. SEM micrographs of Exiligada shells. A-C, E. negriensis Iredale, 1939 (WAM S49152). 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. brabyi sp. nov. (paratype WAM S49159). 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 8. Penial anatomy of E. negriensis Iredale, 1939 (WAM S49216). Scale bar = 5 mm.