Arxellia erythrea, Vilvens, Claude, Williams, Suzanne T. & Herbert, David G., 2014

Vilvens, Claude, Williams, Suzanne T. & Herbert, David G., 2014, New genus Arxellia with new species of Solariellidae (Gastropoda: Trochoidea) from New Caledonia, Papua New Guinea, Philippines, Western Australia, Vanuatu and Tonga, Zootaxa 3826 (1), pp. 255-281 : 278-280

Arxellia erythrea n. sp.

( Figs 9 , 94–103 , Table 8 )

Type material. Holotype (5.5 x 5.4 mm) MNHN IM- 2000-27391. Paratypes: 4 MNHN IM- 2000-27392, IM- 2000- 27393, 2 NHMUK 20140012, 1 coll. C. Vilvens (CV2014-DW1586).

Type locality. Tonga, Vava'u group, BORDAU 2, stn DW1586, 18°34'S, 173°55'W, 440– 487 m.

Material examined. Tonga. BORDAU 2: stn DW1518, 21°21'S, 175°07'W, 336–347 m, 1 dd.—Stn DW1544, 21°18'S, 175°18'W, 441–443 m, 8 lv, 4 dd sub (with 1 paratype MNHN IM- 2000-27393 and 2 paratypes NHMUK 20140012).—Stn DW1585, 18°33'S, 173°57'W, 578 m, 1 dd sub (paratype CV2014-DW1586).—Stn DW1586, 18°34'S, 173°55'W, 440–487 m, 13 lv (with holotype and 3 paratypes MNHN IM- 2000-27392). Wallis and Futuna Islands area. Wallis Island, MUSORSTOM 7: stn DW523, 13°12'S, 176°16'W, 455–515 m, 1 dd.—Stn DW608, 13°22'S, 176°08'W, 440–458 m, 2 dd sub.—Waterwitch Bank, MUSORSTOM 7: stn DW535, 12°30'S, 176°41'W, 340–470 m, 1 dd sub.—Stn DW537, 12°30'S, 176°41'W, 325–400 m, 1 lv.

Distribution. Tonga, 347–578 m (living at 441–443 m); Wallis and Futuna Islands area, 400–455 m (living at 325–400 m).

Description. Shell: Size small for genus (height up to 5.7 mm, width up to 5.4 mm), conical, slightly higher than wide; height 1.0–1.2x width, 3.6–3.9x aperture height; periphery subangular. Protoconch paucispiral, diameter approx. 300–310 µm, rounded, with 5 thin, equally spaced spiral threads; terminal lip straight, without varix. Teleoconch of up to 5.2 whorls; first two whorls moderately convex, subsequent whorls almost straight; shoulder oblique, with angulate rim on early whorls, horizontal on later whorls; whorls sculptured by up to 12 spiral cords, with peripheral cord forming a carina; adapical cords beaded, other cords subgranular to nearly smooth. Suture canaliculate on early whorls, not so on final whorl. First whorl sculptured from start by 5 thin, more or less equally spaced, spiral cords; P1 rapidly forming rim of shoulder; P5 soon level with suture; faint, close-set axial threads between cords. On second whorl, P1 stronger than other cords; S1 arising in middle of whorl and axial threads evanescing. On third whorl, prosocline axial folds develop, stronger on subsutural area and adapical part, rendering P1 subgranular; P1 and P5 strongest, P5 smooth, forming weak suprasutural carina; P3 and P4 very weak; P6 emerging from suture. On fourth whorl, P1 and P2 coarsely beaded, other cords nearly smooth; P5 forming strong carina; P3 and P4 stronger; S3, S4 and S5 arise near end of whorl or at beginning of next whorl. On fifth whorl, additional tertiary cords may arise, especially one cord between suture and P1, rapidly becoming beaded; shoulder more or less horizontal, suture not canaliculate; axial folds much weaker, but still visible. On last whorl, S6 arising at periphery, number of spiral cords reaching 12. Aperture subcircular; peristome incomplete; outer and inner lips slightly thickened at rim; columella vertical, shallowly concave, its edge weakly reflected; a small flange sometimes present at columella base. Base almost flat, with 3–4 thin, smooth spiral cords below periphery, a nearly smooth median area and 2–3 strong, beaded, peri-umbilical cords; innermost cord forming rim of umbilicus, at least twice as thick as penultimate cord, with coarse, weakly pointed beads. Umbilicus deep, wide (diameter ca. 22–32% of shell width), funnel shaped, with angulate rim, interior wall almost straight, bearing 6–7 equally spaced, strong, smooth spiral cords; intervals between spiral cords 0.5–1.0x width of cords.

Colour: First three teleoconch whorls white; subsequent whorls reddish or pinkish with a whitish subsutural area; base nacreous pinkish-white to white; protoconch white.

Remarks. Arxellia erythrea resembles the type species Arxellia trochos from southern New Caledonia ( Figs 1 , 12–24 ) but the present species is a little smaller and more depressed, has thinner and more numerous spiral cords on the whorls, of which P5 forms a more prominent suprasutural cord. In addition, it has a greater H/HA ratio and the colour is predominantly reddish (instead of white to greyish-blue). Since only dry material was available, there are no molecular data for this species.

Etymology. Red (Greek: ερυθροζ, α, ον adjective)—referring to the red background colour of the adult shell whorls.

We thank P. Bouchet (MNHN) for reading the manuscript, constructive advice and access to the malacological resources of the MNHN and Carole Hickman and Bruce Marshall for valuable comments that resulted in an improved manuscript. We are also grateful to V. Héros, B. Buge, P. Maestrati and N. Puillandre (MNHN) for sorting samples and providing locality data, and B. Buge, V. Héros and A. Salvador (NHMUK) for providing registration numbers. Special thanks go to A. Warén (SMNH) for his careful analysis and sorting of the huge MNHN collection of solariellid material and to H. Taylor (NHMUK photo unit) for taking photos of holotypes. We also gratefully acknowledge S. Slack-Smith, C. Whisson and J. Fromont (WAM) for the loan of type material from their institution.

Figures

FIGURES 1 – 9. Arxellia new species, all holotypes except A. tenorioi. 1, A. trochos, n. sp., type species of Arxellia n. gen. 2, A. boucheti n. sp. 3, A. herosae n. sp. 4, A. helicoides n. sp. 5, A. tenorioi n. sp. 6, A. tracheia n. sp. 7, A. maestratii n. sp. 8, A. thaumasta n. sp. 9, A. erythrea n. sp. Scale bar = 5 mm.

FIGURES 94 – 103. Arxellia erythrea n. sp. 94 – 95, holotype MNHN IM- 2000 - 27391, Tonga, Vava'u group, 440 – 487 m [BORDAU 2, stn DW 1586], 5.5 x 5.4 mm. 96 – 100, paratype MNHN IM- 2000 - 27392, Tonga, Vava'u group, 578 m [BORDAU 2, stn DW 1585], subadult. 96 – 98, shell, 4.1 x 4.1. 99, details of protoconch and early whorls. 100, details of columella and umbilicus. 101 – 103, MNHN, Waterwitch Bank, 325 – 400 m [MUSORSTOM 7, stn DW 537], 5.2 x 5.1 mm. Scale bars = 5 mm, except figs. 99, 100: 100 µm.

FIGURES 12 – 24. Arxellia trochos n. sp., New Caledonia. 12 – 14, holotype MNHN IM- 2009 - 23092, Banc de l’Orne / Walope, 400 – 520 m [EXBODI, stn DW 3862], 5.9 x 5.3 mm. 15 – 18, paratype MNHN IM- 2009 - 23109, Banc Sur Durand, 471 – 510 m [EXBODI, stn CP 3851]. 15 – 16, shell, 6.8 x 6.7 mm. 17, details of protoconch and early whorls; 18, details of columella, umbilicus and aperture. 19, paratype MNHN IM- 2009 - 23094, Banc de l’Orne / Walope, 425 – 490 m [EXBODI, stn DW 3861], 6.6 x 6.0 mm. 20 – 22, MNHN, 435 m [BIOCAL, stn DW 08], 6.3 x 5.8 mm. 23 – 24, paratype MNHN IM- 2009 - 23089, radula. 23, entire width of radula ribbon. 24, central field. Scale bar = 5 mm, except figs. 17, 23: 100 µm, fig. 18: 200 µm, fig. 24: 20 µm.

Tables

TABLE 8. Arxellia erythrea n. sp.: shell dimensions for type specimens.

	TW	H	W	HA	H/W	H/HA H/TW
holotype MNHN IM-2000-27391	5.2	5.5	5.4	1.4	1.02	3.93 1.06
paratype MNHN IM-2000-27393	5.1	5.4	4.9	1.5	1.10	3.60 1.06
paratype MNHN IM-2000-27392	4.9	5.7	5.4	1.6	1.06	3.56 1.16
paratype MNHN IM-2000-27392	4.9	5.4	5.2	1.4	1.04	3.86 1.10
paratype MNHN IM-2000-27392	4.9	5.0	4.1	1.4	1.22	3.57 1.02
paratype NHMUK 20140012	5.1	5.2	5.1	1.4	1.02	3.71 1.02
paratype NHMUK 20140012	5.0	5.1	4.9	1.3	1.04	3.92 1.02
paratype CV2014-DW1586	4.7	4.2	4.2	1.1	1.00	3.82 0.89
Acknowledgements