Arxellia maestratii, 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 : 276-278

Arxellia maestratii n. sp.

( Figs 7 , 85–93 , Table 7 )

Type material. Holotype (4.8 x 4.8 mm) MNHN ( IM- 2000-27389). Paratypes: 4 MNHN ( IM- 2000-27390), 2 NHMUK 20140011, 1 coll. C. Vilvens (CV2009-DW972).

Type locality. Vanuatu, MUSORSTOM 8, stn DW972, 19°22'S, 169°28'E, 487– 507 m.

Material examined. Vanuatu. VOLSMAR: stn DW51, 20°59'S, 170°03'E, 450 m, 3 dd, 1 dd juv.—MUSORSTOM 8: stn DW972, 19°22'S, 169°28'E, 487–507 m, 30 dd, 5 dd juv (with holotype, paratypes IM- 2000-27390, paratypes NHMUK and paratype C.Vilvens).—Stn DW977, 19°25'S, 169°29'E, 410–505 m, 2 dd.—Stn CP963, 20°20'S, 169°49'E, 400–440 m, 1 dd. Western Pacific, Wallis Island. MUSORSTOM 7: stn DW604, 13°21'S, 176°08'W, 415–420 m, 17 dd, 20 dd sub, 6 dd juv.

Distribution. Vanuatu, 440–487 m (dead); Wallis Island, 415–420 m (dead).

Description. Shell: Size small for genus (height up to 5.7 mm, width up to 5.2 mm), conical, slightly higher than wide; height 1.0–1.1x width, 3.2–3.9x aperture height; periphery subangular, tricarinate. Protoconch paucispiral, diameter approx. 320 µm, rounded, with 5 thin, unequally spaced spiral threads; terminal lip straight, without varix. Teleoconch of up to 5.5 whorls; first two whorls convex, subsequent whorls straight; shoulder oblique with angulate rim on first two whorls, horizontal thereafter; whorls with up to 8 spiral cords; cords smooth and thin on early whorls, subsequently adapical cords becoming beaded and abapical cords subgranular. Suture moderately 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 forming rim of shoulder at end of whorl; P5 very close to suture; no axial threads visible. On second whorl, all cords remaining similar in strength. On third whorl, prosocline axial folds develop at start of whorl, stronger on subsutural area and adapical part, rendering P1 and P2 subgranular; secondary cord S1 arising and rapidly equalling P2 and P 3 in strength; P1 strongest; P4 strengthening but remaining weaker than P1, subgranular, forming suprasutural carina. On fourth whorl, P1 and P4 strongest, P2 and P3 weakest, P5 covered by suture; S 3 may arise on some specimens; shoulder more or less horizontal, suture not canaliculate. On fifth whorl, S1 only slightly weaker than P1, clearly beaded. On last whorl, S5 arising and P5 emerging from suture, almost smooth, in combination with P4 forming a tricarinate periphery; adapical cords more strongly beaded than abapical one; sometimes with additional tertiary cords on large specimens (e.g. specimens from Wallis Is.). Aperture subcircular; peristome incomplete; inner and outer lips thin at rim; angulation at base of columella obtuse. Columella concave, with small basal flange, weakly reflected. Base almost flat, with one subperipheral cord (sometimes two in large specimens) and two strong, close-set, beaded cords bordering umbilicus, innermost of which is strongest; both peri-umbilical cords with coarse nodules; intermediate portion of base nearly smooth. Umbilicus deep, narrow (diameter ca. 6–10% of shell width), funnel-shaped, with angulate rim; interior wall with 4–6 thick spiral cords.

Colour: Early teleoconch whorls and base nacreous white; subsequent whorls nacreous pinkish-white ( Vanuatu specimens) to completely white ( Wallis Is. specimens); protoconch white.

Remarks. Arxellia maestratii resembles A. trochos from southern New Caledonia ( Figs 1 , 12–24 ) but the former species has fewer, thinner and more widely spaced spiral cords, a greater H/HA ratio, a smooth median area on the base, a narrower umbilicus and peri-umbilical granules that are not elongated. Arxellia maestratii also resembles A. herosae , likewise from southern New Caledonia ( Figs 5 , 42–51 ), but the present species is smaller and slightly more elevated, and has P4 (instead of P5) forming the characteristic suprasutural carina of Arxellia . Furthermore, it has a flatter base with an umbilicus that is not appreciably occluded by any callus deposit. Since only dry material was available, there are no molecular data for this species.

Etymology. Named after Philippe Maestrati (MNHN) whose availability, helpfulness and efficiency are highly appreciated by all malacologists collaborating with the MNHN.

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 85 – 93. Arxellia maestratii n. sp., southern New Caledonia, Norfolk Ridge. 85 – 89, holotype MNHN IM- 2000 - 27389, Vanuatu, 487 – 507 m [MUSORSTOM 8, stn DW 972], 4.8 x 4.8 mm. 85 – 87, shell. 7.0 x 7.2 mm. 88, details of protoconch and early whorls. 89, details of columella and umbilicus. 90 – 91, MNHN, Vanuatu, 410 – 505 m [MUSORSTOM 8, stn DW 977], 5.6 x 5.2 mm. 92 – 93, MNHN, Wallis Island, 415 – 420 m [MUSORSTOM 7, stn DW 604], 4.8 x 4.8 mm. Scale bars = 5 mm, except fig. 88: 100 µm, fig. 89: 500 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.

FIGURES 42 – 51. Arxellia herosae n. sp., southern New Caledonia, Norfolk Ridge. 42 – 46, holotype MNHN IM- 2009 - 28739, Banc Kaimon Maru, 298 – 324 m [NORFOLK 1, stn DW 1679]. 42 – 44, shell, 7.0 x 7.2 mm. 45, details of protoconch and early whorls. 46, details of columella and aperture. 47 – 49, paratype NHMUK 20140008, Banc Eponge, 509 – 513 m [NORFOLK 1, stn DW 1691], 5.2 x 5.9 mm. 50 – 51, MNHN, New Caledonia, 505 – 515 m [BIOCAL, stn DW 66], 7.3 x 6.7 mm. Scale bars = 5 mm, except figs. 45, 46: 100 µm.

Tables

TABLE 7. Arxellia maestratii n. sp.: shell dimensions for type specimens.

	TW	H	W	HA	H/W	H/HA H/TW
holotype MNHN IM-2000-27389	5.0	4.8	4.8	1.3	1.00	3.69 0.96
paratype MNHN IM2000-27390	5.1	4.8	4.9	1.5	0.98	3.20 0.94
paratype MNHN IM-2000-27390	5.2	5.5	5.1	1.6	1.08	3.44 1.06
paratype MNHN IM-2000-27390	5.1	5.5	5.2	1.6	1.06	3.44 1.08
paratype MNHN IM-2000-27390	5.1	5.3	5.2	1.4	1.02	3.79 1.04
paratype NHMUK 20140011	4.9	4.9	4.9	1.4	1.00	3.50 1.00
paratype NHMUK 20140011	5.5	5.7	5.1	1.5	1.12	3.80 1.04
paratype CV2009-DW972	5.1	5.4	5.2	1.4	1.04	3.86 1.06