Pterodacna boucheti, 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 : 20-22

Pterodacna boucheti gen. et sp. nov.

urn:lsid:zoobank.org:act:CDBAC4BE-2727-48F8-85BA-D9326A23B322

Figs 9–11

Diagnosis

See generic diagnosis.

Etymology

Named for Prof. Philippe Bouchet (MNHN) in recognition of the numerous expeditions he has organised, which have led to the discovery of so many fascinating creatures, including this minute limpet.

Material examined

Holotype

WALTERS SHOAL • living specimen; slopes, stn CP4906; 33°26′ S, 44°00′ E; depth 799–837 m; 9 May 2017; alive on decomposing bird feather, DNA tissue sample; MNHN-IM-2013-67323 .

Paratypes

WALTERS SHOAL • 12 specimens, living;same collection data as for holotype; MNHN-IM-2000-38245 .

Description

SHELL. Very small (length up to 1.9 mm), thin and fragile, basal outline more or less evenly elliptical, broadest medially, anterior and posterior ends of similar shape, basal profile flat; L/D=1.47–1.55, H/L ± 0.5; apex at ±0.2 of length from posterior end; anterior slope convex; posterior slope for the most part straight, sometimes slightly bulging in mid-region; interior lacking apical septum. Teleoconch sculptured with occasional irregular collabral growth-lines and faint, close-set, microscopic, concentric ripples; radial sculpture mostly absent, but anterior third with shallow, radial undulations ( Fig. 10C ).

PROTOCONCH ( Fig. 10D–E ). Elliptical, length ± 185 μm, width ± 130 μm, apical portion long and slender, fused to terminal lip, separated from subsequent part of protoconch by a shallowly curved groove; microsculpture comprising a crisp and irregular pattern of close-set, minute pits, most evident apically; terminal lip gently convex, not thickened.

COLOUR. Uniformly translucent milky white, with yellowish colour of body showing through apically.

DIMENSIONS. Holotype, length 1.90 mm, diameter 1.25 mm, height 1.00 mm (= largest specimen).

EXTERNAL ANATOMY ( Fig. 10F ). Animal mostly whitish except for apical part of visceral hump which is tinged yellowish-brown; head with well-developed, distally expanded snout, with roundly D-shaped oral disc with rounded rim; cephalic tentacles stout; pigmented eyes lacking; foot broadly ovate, somewhat truncated anteriorly; two small epipodial tentacles present at rear of foot; mantle edge simple.

RADULA ( Fig. 11 ). Formula ∞ +5+ 1+5 +∞, with up to 32 transverse rows of teeth, rows of asplayed M-shape, lateral 5 is most anterior tooth; rachidian with trigonal base-plate, anterior shaft tapering to rounded tip, lacking cusp; innermost lateral large, its outer anterior margin broadly expanded, antero-medial corner with small irregularly shaped cusp, usually bluntly rounded; laterals 2–4 progressively smaller and less triangular, cusp of lateral 2 an oblique blunt ridge, cusp of lateral 4 small and bluntly rounded, that of lateral 3 of intermediate shape; lateral 5 much larger, its cusp with three robust trigonal denticles, anterior face of cusp base angular. Inner four marginals relatively stout with recurved nondenticulate cusps. Thereafter marginals progressively more slender, their recurved cusps with pectinate margins; cusps of outermost marginals less strongly recurved, broader and more spathulate. Latero-marginal structures not evident. In folded state, laterals 2–4 lie behind lateral 1 and central field is overlain by lateral 5 and marginals.

Distribution

Known only from the slopes of Walters Shoal, at depths of 799– 837 m. Living on decomposing bird feather.

Remarks

See remarks under genus description.

Figures

Fig. 9. Pterodacna boucheti gen. et sp. nov., specimens in situ (arrows) on the barbs and rachis of decomposing bird feather. Scale bars=2.0 mm. Images courtesy of Alain Barrère/MNHN.

Fig. 10. Pterodacna boucheti gen. et sp. nov. A. Holotype, side view, basal length 1.9 mm (MNHN- IM-2013-67323). B. Dorsal view, length 1.7 mm (paratype, MNHN-IM-2000-38245). C. Sculptural detail of holotype, scale bar =100 μm. D. Protoconch of holotype, scale bar = 100 μm. E. Pitted microsculpture of protoconch, scale bar =25 μm (paratype, MNHN-IM-2000-38245). F. Ventral view of preserved specimen, scale bar =250 μm (paratype, MNHN-IM-2000-38245).

Fig. 11. Pterodacna boucheti gen. et sp. nov., radula (paratype, MNHN-IM-2000-38245). A. Entire width of radula, anterior third, scale bar = 25 μm. B. Entire width of radula, posterior third, laterals 2–4 folded behind lateral 1, scale bar= 25 μm. C. Detail of rachidian, lateral and inner marginal teeth, scale bar =10 μm. D. Details of marginal teeth, scale bar =10 μm.