Amplirhagada euroa, Köhler, 2010

Köhler, Frank, 2010, Uncovering Local Endemism in the Kimberley, Western Australia: Description of New Species of the Genus Amplirhagada Iredale, 1933 (Pulmonata: Camaenidae), Records of the Australian Museum 62 (2), pp. 217-284 : 220-221

Amplirhagada euroa n.sp.

Type locality ( Fig. 1 ). Western Australia, eastern Kimberley, Cambridge Gulf, eastern section of Adolphus Island , 15°06'32"S 128°09'08"E; KIS 3–113. East-facing gully with ephemeral stream and patches of vine thicket, fig trees. Scree on very steep slopes. In loose soil under large boulders (leg. V. Kessner, 7 August 2008) .

Type material. Holotype WAM S34601 (Pl. 1.1) . Paratypes AMS C463680 (6 preserved specimens, as holotype), WAM S37083 (12

preserved specimens, as holotype), WAM S37390 (3 shells, 15°06'18"S 128°09'04"E) , WAM S37391 (shell, 15°06'35"S 128°09'57"E) , AMS C463723 (6 shells, 15°06'32"S 128°09'08"E), WAM S37392 (11 shells, 15°06'32"S 128°09'08"E) , WAM S37393 (3 shells, north of Adolphus Island , 15°04'19"S 128°08'18"E) .

Etymology. From euroa (Latin = eastern), for this species occurring at the easternmost limits of the known range of the genus.

Sealing strategy. Rock sealer.

Shell ( Fig. 2A–B , Pl. 1.1–2). Broadly conical with low to medium high spire, thin to translucent. Periphery evenly rounded to slightly angulate; upper and basal sectors of whorls rounded. Umbilicus open, narrowly winding, 50–90 percent concealed by columellar reflection. Background colour yellowish brown with chestnut brown, thin to moderately broad, diffuse to well defined sub-sutural and mid-whorl bands, clearly visible on last whorls only; ventral colour brownish horn to whitish; outer lip colour tends to be lighter than shell till whitish; inner lip translucent. Protoconch c. 3 mm in diameter, comprising about 1.7 whorls, with faint, indistinct axial riblets. Teleoconch with fine axial lirae, curved if viewed from above, pointed in cross-section, irregularly spaced, spaces as wide as thickness of lirae. Lirae evenly distributed across whorl diameter, with reduced height underneath suture; present on all whorls. Angle of aperture 45°. Outer lip simple rounded, sharp, slightly to well expanded, slightly reflected; basal node absent or very weak; palatal node absent. Parietal wall of inner lip absent or inconspicuous.

Pallial morphology. Pallial cavity deep, extending one whorl; mottled or spotted black mantle pigmentation. Kidney extending about half of pallial cavity.

Genital morphology ( Figs. 3–4 ). Penis straight, more or less of same length as anterior part of oviduct. Vas deferens coils before entering penis. Penial retractor muscle shorter than penis complex. Penial verge short, less than 1 ⁄ 5 of length of penial chamber, slender with rounded tip. Penial wall pustules normal to elongated, arranged in rows over entire length of inner penial wall. Main stimulatory pilaster large, cone-shaped, comprising entire length of inner penial wall; sculptured by ridges with smooth, flattened pustules. Vas deferens entering penial sheath in upper third. Vagina of medium length, posteriorly inflated; inner vaginal wall supports undulating longitudinal pilasters. Spermatheca short, reaching base of spermoviduct; duct wide, inner wall with smooth longitudinal pilasters; head globular to elongately inflated, connected with oviduct by connective tissue, wall of head delicate, smooth. Free oviduct rather straight comprising about half of length of anterior part of oviduct. Spermoviduct longer than anterior part of oviduct. Talon embedded in albumen gland close to anterior end of albumen gland.

Radular morphology ( Fig. 2C–E ). Rectangular. Tooth formula C+12–13+3–4+20–21. Average number of rows of teeth 146±7 with 36.2±0.7 rows of teeth per mm (n = 2). Central teeth with sharply pointed triangular mesocones, shorter than base of tooth; ectocones vestigial. Lateral teeth with bluntly pointed triangular mesocones, length equal to base of tooth; small ectocones; endocones absent. Marginal teeth multicuspic, mesocone and endocone similar in length, ectocone smaller than endocone, occasionally subdivided.

Comparative remarks. Amplirhagada euroa is geographically well separated from most other congeneric species. Amplirhagada cambridgensis Solem, 1988 (from the western bank of Cambridge Sound) and A. questronana Solem, 1981a (from El Questro Station near Wyndham, c. 100 km S of Adolphus Island) occur in closer proximity. The shell of A. cambridgensis is very similar but this species differs in the morphology of the inner penial wall with pustules being arranged to form corrugated longitudinal pilasters. Amplirhagada euroa differs from A. questronana by umbilicus forming a chink instead of being open and by its long main stimulatory pilaster that supports flattened pustules ( A. questronana has a short pilaster with corrugations). Otherwise, both species have rather similar shells with regard to shape and size.

Figures

Figure 1. Distribution of Amplirhagada species in the Kimberley region, northwestern Australia. (1) A. euroa n.sp., Adolphus Island. (2) A. solemiana n.sp., Middle Osborn Island. (3) A. indistincta n.sp., Southwest Osborn Island, Kidney Island. (4) A. combeana, Cassini Island. (5) A. mckenziei n.sp., Oliver Island. (6) A. ponderi n.sp., Kingsmill Island. (7) A. montesquieuana n.sp., Fenelon Island. (8) A. descartesana n.sp., Descartes Island. (9) A. katerana, Katers Island. (10) A. puescheli n.sp., unnamed island near Prudhoe Island. (11) A. decora n.sp., A. kessneri n.sp., Bigge Island. (12) A. berthierana n.sp., Berthier Island. (13) A. lamarckiana n.sp., Lamarck Island.(14) A. anderdonensis n.sp., unnamed island, Anderdon Islands. (15) A. tricenaria n.sp., Prince Frederick Harbour, north of Hunter River mouth. (16) A. regia n.sp., A. boongareensis n.sp., A. gibsoni n.sp., and Amplirhagada sp., Boongaree Island. (17) A. yorkensis n.sp., Coronation Island. (18) A. buffonensis n.sp., Buffon Island. (19) A. uwinsensis n.sp., Uwins Island. (20) A. sphaeroidea n.sp., St. Andrews Island. (21) A. basilica n.sp., and A. camdenensis n.sp., Augustus Island. (22) A. kimberleyana n.sp., NW of Wilson Point. (23) A. gemina n.sp., 1.5 km SE of Hall Point. (24) A. dubitabile n.sp., Steep Island. (25) A. napierana, north Napier ranges. (26) A. percita, Napier ranges. (27) A. castra, A. mitchelliana, and A. varia, Mitchell Plateau.

Figure 2. SEM photographs of Amplirhagada euroa n.sp., paratype AMS C463680: (A) apical whorl viewed from above (scale 200 µm); (B) penultimate whorls viewed from above (scale 200 µm); (C) central and lateral radular teeth (scale 20 µm); (D) details of central and lateral teeth (scale 10 µm); (E) details of outer lateral and inner marginal teeth (scale 10 µm); (F) jaw (scale 100 µm).

Figure 3. Genitalia of Amplirhagada euroa n.sp., paratype AMS C463680 (7 August, scale 10 mm). Labelling of structures: ag, albumen gland; hd, hermaphroditic duct; p, penial complex (penis and penis sheath); ov, oviduct (free anterior part); rm, penial retractor muscle; sd, spermathecal duct; sh, spermathecal head; sp, spermoviduct (uterus, prostate); t, talon; va,vagina; vd, vas deferens.

Figure 4. Interior of penial chamber of Amplirhagada euroa n.sp., paratype AMS C463680 (7 August, scale 5 mm). Labelling of structures: iw, inner penial wall; lp, longitudinal (main) pilaster; rm, penial retractor muscle; sh, penial sheath; vd, vas deferens; vg, penial verge.