Spinicalliotropis lepidota, 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 : 29-31

Spinicalliotropis lepidota sp. nov.

urn:lsid:zoobank.org:act:D5DFC0BB-04A2-455D-B28D-E84E01333B93

Fig. 13H–J

Diagnosis

Shell small, elevated-trochiform (H/D ± 1.20), apical angle 56°, uniformly whitish; protoconch globose, exsert; teleoconch sculptured by angular spiral cords, crossed and rendered spinose by crisp axial ribs; spire whorls with only two spiral cords (P1 and P2); ribs raised to form scale-like spines where they cross cords on later whorls; base with three conspicuously spinose spiral cords below P3, which emerges at insertion of outer lip; umbilicus of moderate width with two weak cords within; aperture subquadrate.

Etymology

From the Greek “ lepis ” (λεπΙς) – “a scale”, and “ lepidotos ” (λεπΙΔΟτΟς) – “scaly”; with reference to the scale-like spines on the spiral cords.

Material examined

Holotype

WALTERS SHOAL • empty shell; slopes, stn DW4893; 33°16′ S, 43°58′ E; depth 623–629 m; 4 May 2017; MNHN-IM-2000-36293 .

Description

SHELL. Small (height 2.9 mm), elevated-trochiform, higher than wide (H/D ±1.2), apical angle 56°; spire whorls with two strong, angular spiral cords, crossed and rendered spinose by crisp axial ribs; suture strongly indented and periphery slightly above mid-whorl; base rounded and umbilicate; teleoconch of 5.25 whorls; part of last adult whorl missing in single specimen available. First teleoconch whorl evenly rounded and with 13–14 smooth axial ribs; two spiral cords develop during second whorl, P1 below adapical suture, P2 at periphery; cords nodular at intersections with axial ribs; cords and ribs strengthening during third and fourth whorls, ribs becoming more crisp and raised to form scale-like spines where they cross cords; those on P1 angled adapically; two weaker secondary spiral cords develop near end of fourth whorl, S1 between P1 and adapical suture and S3 below P2; secondary cords also spinose; P3 emerges level with suture on last adult whorl, below periphery; a further, weak secondary cord S2 arises between P1 and P 2 in final quarter whorl, resulting in total of six spiral cords above and including P3 just prior to outer lip; axial ribs somewhat thinner and more numerous in this region. Base with 3 strong spiral cords below P3 and slightly weaker fourth at edge of umbilicus; basal cords conspicuously spinose and somewhat more close-set than those above periphery; umbilicus of moderate width, its interior with additional faint cord. Aperture subquadrate; peristome interrupted in parietal region; inner lip strongly concave below insertion of columella onto paries; edge of outer lip thin, somewhat damaged in specimen available; interior chalky white, retaining traces of nacre.

PROTOCONCH. Translucent pale greyish-white; globose, strongly exsert, comprising approx. 1.25 whorls, diameter 260 μm.

COLOUR. Uniformly whitish with traces of underlying nacre visible in places.

DIMENSIONS. Holotype, height 2.9 mm, diameter 2.5 mm (estimated by extension of evenly conical spire profile).

Distribution

Known only from the slopes of Walters Shoal, at a depth of 623–629 m; living specimens unknown.

Remarks

Spinicalliotropis lepidota sp. nov. has a more acute spire than all other species currently referred to the genus ( Table 1 ). In addition, although the holotype has only slightly fewer teleoconch whorls, it is substantially smaller than the other species. Three species of Spinicalliotropis have been recorded from the south-western Indian Ocean: S. ericius ( Vilvens, 2006) , S. solariellaformis ( Vilvens, 2006) and S. stephanos Vilvens, 2021 , but besides being larger and broader, all have three primary spiral cords on the middle spire whorls (only two in S. lepidota ). The spiral cords on the base of S. lepidota are also more conspicuously and sharply spinose. S. stephanos has a much narrower umbilicus. Calliotropis acherontis Marshall, 1979 , which also occurs in the south-western Indian Ocean ( Vilvens 2006, 2021; Herbert 2015) and has a narrowly conical shell, is larger (height up to 5.0 mm) and lacks the spinose sculpture typical of species of Spinicalliotropis .

Whilst I hesitate to describe a new species based on a single somewhat damaged specimen, the shell is for the most part in good condition and evinces characters that clearly set it apart from others in the genus, as detailed above.

Figures

Fig. 13. A–C. Calliotropis eucheloides Marshall, 1979. A. Apertural view showing duplex tooth at base of columella, Walters Shoal, stn DW4904, diameter 12.0 mm (MNHN-IM-2013-67241). B–C. Apical and basal views, Walters Shoal, stn DW4892, diameter 10.6 mm (MNHN). D–F. Calliotropis velata Vilvens, 2006, Walters Shoal, stn CP4910, diameter 15.9 mm (MNHN-IM-2013-67242). G. Calliotropis eucheloides, living animal, shell diameter 12.2 mm (MNHN-IM-2013-67240), image courtesy of Alain Barrère/MNHN. H–J. Spinicalliotropis lepidota sp. nov., holotype, height 2.9 mm (MNHN- IM-2000-36293).