Amplirhagada gemina, 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 : 270-271

Amplirhagada gemina n.sp.

Type locality ( Fig. 1 ). Western Australia, Kimberley, Bonaparte Archipelago, Camden Sound , mainland 4.5 km N of Prior Point, 1.5 km SE of Hall Point; KC-005 (leg. V. Kessner & A. Longbottom, 09 July 1988) .

Type material. Holotype WAM S34626 (Pl. 2.14) . Paratypes AMS C463761 (preserved specimen), FMNH 219049 (5 preserved specimens), WAM S41479 (3 preserved specimens) .

Etymology. From gemina (Latin = twin-born), in reference to its close overall similarity with its sibling species A. kimberleyana .

Shell ( Fig. 82A–C , Pl. 2.14). Semi-globose to broadly conical, with medium spire, thin to solid (translucent). Periphery evenly rounded to slightly angulate; upper and basal sectors of whorls rounded. Umbilicus forming a chink to narrowly winding opening, 60–100 percent concealed by columellar reflection. Background colour beige brown sub-sutural band absent or diffuse, brown; mid-whorl band absent or diffuse, brown, thin, visible on last whorl only; ventral colour lighter, horn or whitish; outer lip colour differs from shell, light brown to whitish; inner lip whitish. Angle of aperture 45°, outer lip moderately thick, slightly expanded, not or slightly reflected, basal and palatal node absent. Teleoconch with pronounced axial growth lines which become more oblique towards the base of the shell. Parietal wall of inner lip inconspicuous.

Pallial morphology. Pallial cavity moderately deep, extending 3 ⁄ 4 whorl; mantle pigmentation mottled, black. Kidney extending about half of pallial cavity.

Genital morphology ( Figs. 83–84 ). Penis straight, more or less of same length as anterior part of oviduct. Vas deferens coils once before entering penis. Penial retractor muscle shorter than penis. Penial verge short (<1 ⁄ 8 penial chamber), slender to spatulate, with pointed tip. Penial wall pustules rather large, arranged in rows on entire wall of penial chamber, becoming more oblique towards base. Main stimulatory pilaster not well differentiated, covered by undifferentiated pustules, comprising apical to median portion of penial chamber. Vas deferens entering penial sheath in upper third. Vagina moderately long, tubular to posteriorly inflated. Inner vaginal wall with smooth longitudinal pilasters. Spermathecal duct wide, inflated, internally with smooth longitudinal pilasters. Spermathecal head elongately inflated, connected with oviduct by connective tissue, internally smooth, with delicate wall. Free oviduct comprising about half of anterior part of oviduct, more or less straight. Posterior parts of genital system unknown.

Radular morphology ( Fig. 82E–F ). Rectangular. Tooth formula C+16+4+20. With 150 rows of teeth, 34.2 rows per mm (n = 1). Central teeth with sharply pointed, triangular mesocones, shorter than base of tooth; ectocones vestigial. Lateral teeth with sharply pointed, triangular mesocones, length equal to base of tooth; ectocones tiny, endocones vestigial. Marginal teeth with elongate to triangular mesocones; ectocones shorter and narrower than mesocones; endocones smaller than ectocones.

Comparative remarks. Smaller than other species with broadly conical to dome-shaped. Inner penial wall pustules larger and denser than in A. kimberleyana . Although morphologically similar, both species are genetically welldifferentiated. Material of the present species has been labelled as “ Amplirhagada sp. 64” by Solem together with material of A. kimberleyana , which has a similar shell.

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 82. SEM photographs of Amplirhagada gemina n.sp. (A–B) Shell, holotype WAM S34626: (A) apical whorl viewed from above (scale 200 µm); (B) sculpture on second whorl viewed from above (scale 100 µm); (C) close-up showing sculpture on penultimate whorl (scale 200 µm). (D) Jaw (scale 100 µm), paratype FMNH 219049. (E–F) Radula, paratype FMNH 219049: (E) central and lateral teeth (scale 20 µm); (F) middle marginal teeth (scale 10 µm).

Figure 83. Genitalia of Amplirhagada gemina n.sp., holotype WAM S34626 (9 July, scale 10 mm). Compare with Fig. 3 for labelling of structures.

Figure 84. Interior of penial chamber of Amplirhagada gemina n.sp., holotype WAM S34626 (9 July, scale 3 mm). Compare with Fig. 4 for labelling of structures.