Tylorhaphe wallacei, Herbert, 2024

Herbert, David G., 2024, The Umboniinae (Mollusca: Gastropoda: Trochidae) of New Caledonia, with descriptions of two new genera and eight new species, plus an additional new species from the Bismarck Sea, European Journal of Taxonomy 973, pp. 1-143 : 118-122

Tylorhaphe wallacei gen. et sp. nov.

urn:lsid:zoobank.org:act:1FC6F4A9-1000-4B89-8C68-C22A43FE818D

Figs 65–67

Diagnosis

Closest to Tylorhaphe luteopicta gen. et sp. nov., but with stronger sculpture, including distinct axial pliculae; periphery less strongly angled; umbilicus narrower, its rim with a strong spiral cord that overhangs the underlying cavity.

Etymology

I take pleasure in naming this remarkably beautiful species in honour of Alfred Russel Wallace (1823– 1913), in recognition of his pioneering contribution to biogeography and evolutionary biology.

Material examined

Holotype ( Fig. 66 )

PAPUA NEW GUINEA • living specimen; New Ireland, south of Selapiu Island , Stn DW 4473; 02°43′ S, 150°36′ E; depth 93–149 m; 4 Sep. 2014; NO Alis -KAVIENG 2014 leg.; MNHN-IM-2000-38878.

Paratypes

PAPUA NEW GUINEA – New Ireland • 9 specimens, living; south east of Selapiu Island, Stn DW4467; 02°44′ S, 150°35′ E; depth 213–287 m; 3 Sep. 2014; NO Alis -KAVIENG 2014 leg.; MNHN- IM-2000-38879 • 1 specimen, living; same data as for holotype; DNA voucher; MNHN-IM-2023-58751 • 6 specimens, living; same data as for holotype; MNHN-IM-2000-38880 • 2 specimens, living; south of Selapiu Island , Stn DW 4462; 02°43′ S, 150°36′ E; depth 90–201 m; 3 Sep. 2014; NO Alis -KAVIENG 2014 leg.; DNA vouchers; MNHN-IM-2013-58616 and -58617 • 1 specimen, living; south of Selapiu Island , Stn DW 4466; 02°43′ S, 150°36′ E; depth 204–272 m; 3 Sep. 2014; NO Alis -KAVIENG 2014 leg.; DNA voucher; MNHN-IM-2023-58916 • 5 specimens, living; south of Selapiu Island , Stn DW 4474; 02°43′ S, 150°36′ E; depth 90–185 m; 4 Sep. 2014; NO Alis -KAVIENG 2014 leg.; MNHN- IM-2000-38881 .

Other material PAPUA NEW GUINEA – New Ireland • 37 specimens, living; south of Selapiu Island , Stn DW 4472; 02°43′S, 150°36′ E; depth 87–144 m; 4 Sep. 2014; NO Alis -KAVIENG 2014 leg.; MNHN • 26 specimens, living; south of Selapiu Island , Stn DW 4465; 02°43′ S, 150°36′ E; depth 90–228 m; 3 Sep. 2014; NO Alis -KAVIENG 2014 leg.; MNHN • 2 specimens, living; south of Selapiu Island , Stn DW 4462; 02°43′ S ,

150°36′ E; depth 90–201 m; 3 Sep. 2014; NO Alis -KAVIENG 2014 leg.; MNHN • 1 specimen, living; south of Selapiu Island, Stn DW 4466; 02°43′ S, 150°36′ E; depth 204–272 m; 3 Sep. 2014; NO Alis - KAVIENG 2014 leg.; MNHN • 29 specimens, living; south of Selapiu Island, Stn DW 4474; 02°43′ S, 150°36′ E; depth 90–185 m; 4 Sep. 2014; NO Alis -KAVIENG 2014 leg.; MNHN .

Description ( Fig. 66 )

SHELL. Small (diameter up to 6.7 mm), depressed-trochiform (H/D 0.57– 0.6); teleoconch of up to 5.0 whorls; periphery roundly angled, situated just below mid-whorl; suture slightly above periphery; base umbilicate, somewhat flattened. First teleoconch whorl rounded with circa three indistinct spiral cords; shoulder develops and strengthens during second and third whorl; two strong cords arise near end of third whorl, one subsutural the other supraperipheral; subsutural cord initially beaded by prosocline subsutural pliculae, but beading progressively stronger with growth and last whorl with strong nodules on subsutural cord; supraperipheral cord remaining more finely beaded, beads aligned with axial pliculae; interval between subsutural and supraperipheral cords a broad, bevelled slope, almost flat, sculptured with finer secondary cords and further intermediaries, initially few but becoming more numerous and more close-set with growth, up to 10 on last whorl; bevelled slope with distinct, close-set, strongly prosocline pliculae which become finer and even more close-set on last whorl; interaction of spiral and axial element producing a finely beaded reticulation; circa three peripheral spiral cords at start of last whorl. Base with similar, but finer cords, all with pliculate intervals; spiral sculpture usually weaker in mid-region of base (not always), but strengthens considerably toward umbilicus with 2–4 strong cords, innermost of which is largest and forms umbilical rim; all peri-umbilical cords rendered nodular by strong axial pliculae radiating from umbilicus. Umbilicus relatively narrow (± 0.22 of maximum shell diameter), steep-sided and deep; its walls retaining traces of spiral and axial sculpture, and overhung by cord at umbilical rim; funicle lacking. Aperture roundly quadrate; peristome interrupted in parietal region; columella pillar thick with a slight basal swelling and micropustular surface; parietal lip thickened with callus and extending outward as a rounded lobe above insertion of columella; surface of lobe microshagreened sometimes with indistinct in-running ridges in the most mature individuals; edge of lobe slightly thickened and with a step-like drop to underside of preceding whorl; outer lip descending steeply immediately prior to its insertion, its interior somewhat thickened and with traces of in-running ridges; interior otherwise smooth and nacreous with external sculpture evident through transparency; outer lip with shallow subperipheral concavity in mature specimens; thickening of outer lip also evident externally as a slight subterminal swelling.

COLOUR. Shell glossy throughout; colour pattern comprising bold bright yellowish subsutural blotches; bevelled slope with alternating yellowish and opaque white axial lines; bolder blotches in similar colours at periphery and extending onto base in a radiating pattern; peri-umbilical region white; apical whorls translucent whitish to pale yellowish-grey, first whorl with a row of opaque white dots at shoulder; apical bulb of protoconch opaque white; yellow colour may turn a pale apricot-brown post mortem in some individuals.

DIMENSIONS. Holotype, height 3.8 mm, diameter 6.5 mm; largest specimen, diameter 6.7 mm.

PROTOCONCH ( Fig. 67B ). As in Tylorhaphe luteopicta gen. et sp. nov., but slightly larger, diameter 220– 230 µm.

OPERCULUM ( Fig. 67C–D ). Corneous; multispiral; peripheral fringe radially striate; radial striations remaining where whorls overlap; surface with distinct spiral microsculpture.

RADULA ( Fig. 67E–F ). Very similar to that of Tylorhaphe luteopicta gen. et sp. nov.; cusp of transitionary innermost marginal trigonal with three small pointed denticles; second marginal clearly the largest tooth, its cusp with a strong triangular central denticle bearing smaller lateral denticles at its base on both sides.

EXTERNAL ANATOMY (from rehydrated specimens, condition poor). Head with distinct forehead between cephalic tentacles; snout moderately long, cylindrical, distal third bearing long slender papillae; cephalic lappets not evident; cephalic tentacles long and slender, micropapillate, eyestalks long, their tips conspicuously expanded and containing large black eyes; left neck-lobe small, digitate; right neck-lobe rolled to form exhalant siphon; details of epipodial structure not clear; foot evidently broad with lateral propodial lobes on each side, tapering posteriorly. Head-foot translucent cream-white with some opaque white pigmentation on snout, eyestalks, right neck-lobe, sides of foot, and metapodium.

Habitat

Dredged on muddy sand; at depths of 144–213 m (living specimens the same).

Distribution ( Fig. 65 )

Known only from off the southern coast of Selapiu Island, New Ireland, Papua New Guinea [Bismarck Sea]. Although dredging at similar depths was undertaken at other localities off north-western New Ireland, this species was only collected in this very limited area. Nevertheless, at this locality the species appears moderately abundant.

Remarks

A highly distinctive, sculpturally ornate species. Most similar to Tylorhaphe luteopicta gen. et sp. nov.

Figures

Fig. 65. Map showing the distribution of Tylorhaphe luteopicta gen. et sp. nov. (squares) and T. wallacei gen. et sp. nov. (circle). Type localities indicated in pink.

Fig. 66. Tylorhaphe wallacei sp. nov. holotype, off Selapiu Island, New Ireland, Papua New Guinea, Stn DW4473, height 3.8 mm, diameter 6.5 mm (MNHN-IM-2000-38878).

Fig. 67. Tylorhaphe wallacei gen. et sp. nov., Selapiu Island, New Ireland. A. Oblique view of apical whorls. B. Protoconch. C. Operculum. D. Detail of operculum showing microscopic spiral sculpture. E. Radula, entire width. F. Radula, latero-marginal transition. A–B. Stn DW4474 (paratype, MNHN- IM-2000-38881). C–F. Stn DW4473 (paratype, MNHN-IM-2000-38880). Scale bars: A=1.0 mm; B, D =100 µm; C =0.5 mm; E =50 µm; F =25 µm.