Herpetopoma (s.l.) xeniolum (Melvill, 1918) Herbert, 2012

Herbert, D. G., 2012, A revision of the Chilodontidae (Gastropoda: Vetigastropoda: Seguenzioidea) of southern Africa and the south-western Indian Ocean, African Invertebrates 53 (2), pp. 381-381 : 444-446

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https://doi.org/ 10.5733/afin.053.0209



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scientific name

Herpetopoma (s.l.) xeniolum (Melvill, 1918)

comb. nov.

Herpetopoma (s.l.) xeniolum (Melvill, 1918) View in CoL comb. n.

Figs 36–38 View Fig View Fig View Fig

Euchelus xeniolum: Melvill 1918: 154 View in CoL , pl. 5, fig. 27. Type loc.: Chabar , Gulf of Oman [= Chah Bahar, Iran], 5 fath. [- 9 m] (Townsend).

Turcica (Perrinia) waiwailevensis: Ladd 1982: 23 , pl. 24, figs 10–13. Type loc.: Station C 2026, Viti Levu, Fiji; Pliocene. Syn. n.

Herpetopoma eboreum: Vilvens & Héros 2003: 61 View in CoL , figs 1–4; Poppe et al. 2006: 36, pl. 10, fig. 2; Poppe & Tagaro 2008: 174, pl. 32, fig. 1. Type loc.: Touho Pass, Touho area, New Caledonia, - 50– 62m. Syn. n.

Euchelus townsendianus View in CoL [non Melvill & Standen, 1903]: Jay 2009.

Type material: Holotype of Euchelus xeniolum Melvill, 1918 in NHMUK (1921.1.28.30); Trew (1987) was in error in stating that there were three specimens registered. Holotype of Turcica (Perrinia) waiwailevensis Ladd, 1982 in USNM (2501420). Holotype of Herpetopoma eboreum Vilvens & Héros, 2003 in MNHN.

Other material examined (all MNHN): RÉUNION: off Ste-Marie (20.867°S 55.633°E), - 110 m, Marion-Dufresne 32, st’n DC126, dredged, 1982; off St-Joseph (21.383°S 55.617°E), - 205–215 m, Marion-Dufresne 32, st’n DR47, dredged, 1982 GoogleMaps ; Réunion, not further localised (M. Jay coll’n) . MADAGASCAR: West of Nosy Be (13.450°S 47.917°E), - 187–247 m, Campagne Miriky, st’n DW3234, dredged, 3.vii.2009 GoogleMaps .

Remarks:A number of samples collected off Réunion are evidently referable this species, which I consider is closer to Herpetopoma than to Euchelus on account of its small size and the U-shaped notch at the columella base (albeit relatively weak). The species is poorly known and has not to my knowledge been recorded subsequent to the original description. The holotype ( Fig. 37A, B View Fig ) has four granular spiral cords on the penultimate whorl as do some Réunion specimens ( Fig. 37C, D View Fig ). However, other specimens in the Réunion samples have five such cords ( Fig. 37E, F View Fig ) and closely resemble the holotype of Turcica (Perrinia) waiwailevensis Ladd, 1982 from the Pliocene of Fiji ( Fig. 37G, H View Fig ). I have no doubt that the Réunion samples belong to a single species and consider the number of spiral cords on the penultimate whorl (four or five) to be a variable character. There is evidently similar variation in the number of spiral cords on the base (6–8). As a consequence, I can find no substantive differences by which to separate Herpetopoma waiwailevensis from H. xeniolum . In addition, H. eboreum Vilvens & Héros, 2003 , described from shallow water off New Caledonia and recorded also from deeper water off the Philippines ( Poppe et al. 2006), appears indistinguishable from H. waiwailevensis . I believe that all three names refer to a single widespread species, for which H. xeniolum is the earliest name. Euchelus hummelincki Moolenbeek & Faber, 1989 from the Caribbean is another similar species, but is evidently smaller (length up to 3.2 mm) and has somewhat coarser sculpture.

The holotype of H. xeniolum was collected in shallow water (- 9 m) and similarly the overall facies of the fauna at the type locality of H. waiwailevensis is that of a shallow-water, lagoonal system ( Ladd 1966, 1982). The depth at which the dredged material from Réunion was obtained (- 110–340 m) would thus seem to be anomalous. However, Réunion has a steeply shelving sublittoral zone and dead specimens of typically shallow-water species are frequently found at greater depths.That the species is also present in the M. Jay collection ( MNHN) suggests that it does indeed occur in relatively shallow water around Réunion. The same may also apply to some rather worn specimens from off the steeply shelving coast of Nosy Be, which I also tentatively identify as H. xeniolum .

This material resembles H.? naokoae (above), but the whorls are less convex and the shell is consistently more elevated, L/D usually>1.23, spire height/aperture height usually> 1.60 in H. xeniolum (usually <1.23 and <1.60 respectively in H.? naokoae ). Additionally, in H.? naokoae the sculpture is coarser and the denticles inside the outer lip, although ridge-like, are restricted to the thickened region just inside the lip edge. In H. xeniolum some of these ridges extend deeply into the aperture. Furthermore, in the local H.? naokoae specimens there is an additional small denticle adjacent to the notch between the two larger denticles at the junction of the base and columella, this is not present in the H. xeniolum material examined.

The protoconch is translucent white with a diameter of ca 220 µm; its surface is eroded in the material available.A microsculpture of irregular vermiform spiral threads is present on the early teleoconch whorls; subsequent whorls with weak oblique vermiform threads and traces of very fine scratch-like marks.


Museum National d'Histoire Naturelle














Herpetopoma (s.l.) xeniolum (Melvill, 1918)

Herbert, D. G. 2012

Herpetopoma eboreum: Vilvens & Héros 2003: 61

POPPE, G. T. & TAGARO, S. P. 2008: 174
POPPE, G. T. & TAGARO, S. P. & DEKKER, H. 2006: 36
VILVENS, C. & HEROS, V. 2003: 61
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