Calliostoma pantopunctatum, Herbert, 2024

Herbert, David G., 2024, The Vetigastropoda (Mollusca) of Walters Shoal, with descriptions of two new genera and thirty new species, European Journal of Taxonomy 923, pp. 1-119 : 67-69

Calliostoma pantopunctatum sp. nov.

urn:lsid:zoobank.org:act:C7DB30D9-F86E-4F8F-8289-4AF393799C34

Figs 27 , 28A–B , 38A–B

Diagnosis

Shell height up to 9.8 mm; spire with flat sides and angular periphery; suture not indented; base flattened, anomphalous in adult; sculpture dominated by granular spiral cords; penultimate whorl with five spiral cords of more or less equal size, above and including periphery; base with 9–10 more or less equally spaced, weakly granular spiral cords; apex milky-white, remainder of shell with numerous ginger-brown spots on a milky-white to pale fawn ground; spots present only on spiral cords, usually on alternate granules and more or less axially aligned.

Etymology

From the Greek “ pas, pant- ” (παντ-) – “all, universal, all over” and the Latin “ punctum, punctatum ” – “a spot, spotted”; in reference to the uniformly spotted colour pattern on the shell.

Material examined

Holotype

WALTERS SHOAL • living specimen; slopes, stn DW4881; 33°16′ S, 43°50′ E; depth 377–382 m; 2 May 2017; DNA tissue sample; MNHN-IM-2013-67275 .

Paratypes

WALTERS SHOAL – slopes • 1 empty shell; stn DW4879; 33°17′ S, 43°52′ E; depth 288–300 m; 1 May 2017; MNHN-IM-2000-34924 • 1 living specimen; stn DW4885; 33°17′ S, 43°55′ E; depth 272–380 m; 3 May 2017; DNA tissue sample; MNHN-IM-2013-67276 • 3 empty shells; stn DW4885; 33°17′ S, 43°55′ E; depth 272–380 m; 3 May 2017; MNHN-IM-2000-34925 • 1 empty shell; stn DW4888; 33°10′ S, 43°57′ E; depth 299–311 m; 3 May 2017; MNHN-IM-2000-34926 • 10 empty shells; stn DW4896; 3°07′ S, 43°51′ E; depth 325–357 m; 5 May 2017; MNHN-IM-2000-34927 • 1 living specimen; stn DW4897; 33°09′ S, 43°59′ E; depth 490–584 m; 5 May 2017; DNA tissue sample; MNHN-IM-2013-67277 .

Other material

WALTERS SHOAL – slopes • 39 empty shells; stn DW4881; 33°16′ S, 43°50′ E; depth 377–382 m; 2 May 2017; MNHN • 1 empty shell; stn DW4886; 33°17′ S, 43°56′ E; depth 573–582 m; 3 May 2017; MNHN • 2 empty shells; stn DW4889; 33°09′ S, 43°58′ E; depth 353–465 m; 3 May 2017; MNHN • 1 empty shell; stn DW4890; 33°09′ S, 43°59′ E; depth 492–588 m; 4 May 2017; MNHN • 1 empty shell; stn DW4898; 33°09′ S, 44°01′ E; depth 652–668 m; 6 May 2017; MNHN .

Description

SHELL. Of small to moderate size (height up to 9.8 mm); spire conical with flat sides and angular periphery, adult height slightly greater than diameter; sculpture dominated by granular spiral cords; suture not indented, no deeper than intervals between spiral cords; base flattened, anomphalous in adult; teleoconch of up to 7.0 whorls. First teleoconch whorl rounded ( Fig. 28A–B ), initially with up to five spiral threads, soon resolving into three primary spiral cords (P1–P3), a fourth (P4) level with abapical suture; P3 strongest; cords crossed by axial ribs and rendered nodular at intersections; P4 rises above suture during third or fourth whorl and secondary spiral (S2) arises during fourth whorl, between P2 and P3; subsequent whorls with five spiral cords, of more or less equal size, above and including periphery; cords bearing rounded granules; cord intervals somewhat wider than cords themselves, particularly that between P1 and P2; cord intervals with fine, close-set, collabral growth-lines. Base with 9–10 more or less equally spaced spiral cords; subperipheral cord level with suture; cords at most weakly granular, almost smooth; intervals wider than cords, sculptured by fine, close-set growth-lines. Aperture roundly rhomboidal; columella oblique to shell axis, somewhat thickened and reflected over umbilical region; outer lip lacking denticles; interior nacreous.

PROTOCONCH ( Fig. 28B ). Somewhat exsert, comprising approx. 1.25 whorls, diameter ± 375 μm; surface sculptured with hexagonal network of interconnected ridges on a smooth background; terminal lip with collabral rib resembling axial ribs on early teleoconch.

COLOUR. Protoconch and first teleoconch whorl milky-white, remainder of shell with milky-white to pale fawn ground, maculated with numerous ginger-brown spots; spots present only on spiral cords, usually on alternate granules and with a more or less axial alignment. Basal colour pattern similar; columella and umbilical region whitish.

DIMENSIONS. Holotype, height 5.8 mm, diameter 5.8 mm; largest specimen, height 9.8 mm, diameter 9.1 mm.

EXTERNAL ANATOMY ( Fig. 38A–B ). Photographs of the living holotype show its external anatomy to conform with that described for Calliostoma by Hickman & McLean (1990). Like the shell, the snout, epipodium and sides of the foot are pigmented with numerous brown spots, although these are a darker reddish-brown compared to the ginger-brown maculations on the shell. The cephalic tentacles are faintly and uniformly tinged with a similar brownish colour.

Distribution

Known only from the slopes of Walters Shoal, at depths of 300–652 m (live-taken material 380–490 m); dredged on substrata of coarse sand and fine gravel, with ophiuroids, octocorals and solitary corals.

Remarks

Calliostoma pantopunctatum sp. nov. is highly distinctive amongst species of Calliostomatinae from the south-western Indian Ocean (cf. Lussi 2014; Vilvens 2014). Characteristic features include its pale apex, finely spotted colour pattern, evenly conical spire profile with no whorl convexity or sutural indentation, and relatively coarse spiral sculpture on the last adult whorl, comprising only five spiral cords above and including the peripheral cord. The presence of only one secondary spiral cord (S2) is also unusual. Calliostoma variegatum Carpenter, 1864 , from the north-east Pacific has a similar spotted colour pattern, but it is considerably larger (height up to 29 mm), has more convex whorls, a more indented suture, and the last adult whorl has a more rounded periphery and more numerous secondary spiral cords ( McLean 1996; Tuskes 2019).

In view of the fact that the supraspecific classification of Calliostoma sensu lato remains far from resolved, I have chosen not to speculate on the affinities of this new species in relation to others. Molecular data suggests some geographically congruent clustering of calliostomatine species ( Williams et al. 2010; Marshall 2016), but as yet no Indian Ocean or southern African species have been included in such studies. Calliostoma pantopunctatum sp. nov. shows some similarity with Fautor Iredale, 1924 , but Marshall (2016) has suggested that this is a tropical south-west Pacific taxon.

Figures

Fig. 27. Calliostoma pantopunctatum sp. nov. A. Holotype, height 5.8 m (MNHN-IM-2013-67275). B–D. Paratype, height 9.8 mm (MNHN-IM-2000-34924).

Fig. 28. A–B. Calliostoma pantopunctatum sp. nov., holotype (MNHN-IM-2013-67275). A. Oblique view of apex showing development of spiral sculpture. B. Sculptural detail of protoconch and early teleoconch. C–F. Bruceina areneformis sp. nov., paratypes C. Side view of spire. D. Umbilical region showing funicle-like cord within. E. Oblique view of apex showing development of spiral sculpture. F. Sculptural detail of protoconch and early teleoconch (C–D = MNHN-IM-2000-35700, E–F =MNHN- IM-2000-35704). Scale bars: A, C= 1.0 mm; B, F =100 μm; D= 500 μm; E =200 μm.

Fig. 38. A–B. Calliostoma pantopunctatum sp. nov., holotype, living animal, shell diameter 5.8 mm (MNHN-IM-2013-67275). C–E. Kaiparathina monticola sp. nov., holotype, living animal, anterolateral structure arrowed, shell diameter 6.8 mm (MNHN-IM-2013-67168). F. Stomatella multilirata sp. nov., Walters Shoal, stn WS03, greatest shell dimension 6.0 mm (MNHN). Images courtesy of Alain Barrère/ MNHN.