Tylorhaphe luteopicta, 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 : 113-118

Tylorhaphe luteopicta gen. et sp. nov.

urn:lsid:zoobank.org:act:EDA653AC-62B0-4D55-A15E-F49763DA184C

Figs 63–65

Diagnosis

Closest to Tylorhaphe wallacei gen. et sp. nov., but lacking well-defined axial sculpture and with more distinctly angled periphery; umbilicus also wider and its rim does not overhang the underlying cavity.

Etymology

From the Latin words ‘ luteus ’, yellow, and ‘ pictus ’, painted; in reference to the yellow subsutural blotches.

Material examined

Holotype ( Fig. 63A–D )

NEW CALEDONIA – Grande Terre • living specimen; north of Île des Pins , Stn CP 4688; 22°29′ S, 167°31′ E; depth 278–353 m; 14 Aug. 2016; NO Alis -KANACONO leg.; MNHN-IM-2000-38874 .

Paratypes

NEW CALEDONIA – Bellona Plateau • 2 specimens, living; Bellona Plateau, Stn DW5047; 22°03′ S, 158°48′ E; depth 280–300 m; 23 Sep. 2017; NO Alis -KANADEEP leg.; MNHN-IM-2000-38875 . – Grande Terre • 1 specimen, living; off Île Toupéti, Stn CP3806; 21°42′ S, 166°34′ E; depth 307– 309 m; 5 Sep. 2011; NO Alis -EXBODI leg.; DNA voucher; MNHN-IM-2009-23261 • 3 specimens, living; south of Île des Pins , Stn CP 4674; 22°48′ S, 167°29′ E; depth 302–311 m; 13 Aug. 2016; NO Alis -KANACONO leg.; DNA vouchers; MNHN-IM-2013-64730, -68704 and -68912 • 2 specimens, living; same collection data as for preceding; MNHN-IM-2000-38876 • 1 specimen, living; north of Île des Pins , Stn CP 4687; 22°29′ S, 167°30′ E; depth 256–268 m; 14 Aug. 2016; NO Alis -KANACONO leg.; DNA voucher; MNHN-IM-2013-63127 • 1 specimen, living, north of Île des Pins , Stn CP 4688; 22°29′ S, 167°31′ E; depth 278–353 m; 14 Aug. 2016; NO Alis -KANACONO leg.; DNA voucher; MNHN-IM-2013-63115 .

SOLOMON ISLANDS • 3 specimens, living; north of Malaita, Stn DW 1768; 08°21′ S, 160°42′ E; depth 194–286 m; 28 Sep. 2001; NO Alis -SALOMON 1 leg.; MNHN-IM-2000-38877 .

Other material

LORD HOWE CHAIN • 1 specimen, dead; Capel Bank, Stn CP 4929; 25°07′ S, 159°50′ E; depth 270 m; 3 Sep. 2017; NO Alis -KANADEEP leg.; MNHN .

SOLOMON ISLANDS • 11 specimens, dead; north of Malaita, Stn DW 1768; 08°21′ S, 160°42′ E; depth 194–286 m; 28 Sep. 2001; NO Alis -SALOMON 1 leg.; MNHN .

NEW CALEDONIA – Grande Terre • 1 specimen, dead; SW of Île des Pins, Stn DW4702; 22°45′ S, 167°18′ E; depth 290–307 m; 17 Aug. 2016; NO Alis -KANACONO leg.; MNHN • 1 specimen, dead; SW of Île des Pins, Stn DW4706; 22°47′ S, 167°24′ E; depth 343–355 m; 17 Aug. 2016; NO Alis - KANACONO leg.; MNHN • 1 specimen, dead; south of Île des Pins , Stn DW 4672; 22°47′ S, 167°26′ E; depth 290–310 m; 13 Aug. 2016; NO Alis -KANACONO leg.; MNHN • 1 specimen, dead; SW of Île des Pins, Stn DW4695; 22°47′ S, 167°27′ E; depth 200–290 m; 15 Aug. 2016; NO Alis -KANACONO leg.; MNHN .

Description ( Fig. 63 )

SHELL. Small (diameter up to 6.5 mm), depressed-trochiform (H/D 0.50–0.63); teleoconch of up to 4.75 whorls; periphery sharply angled and keel-like, situated close to mid-whorl; suture level with periphery; base widely umbilicate. First teleoconch whorl rounded with 3–4 spiral lirae, the upper one strongest and strengthening further during second whorl where it delineates a distinct shoulder; remaining lirae evanescing by start of third whorl; early axial sculpture comprising only thin, rather widely-spaced axial threads (in addition to typical umboniine axial microsculpture); these strengthening to become distinct axial pliculae during second whorl, forming beads on shoulder cord; a low subsutural cord arises during third whorl, strengthening rapidly thereafter and developing strong, widely-spaced nodules ( Fig. 64A ); shoulder cord evanescing during fourth whorl and replaced by a smooth supraperipheral cord lying between periphery and nodular subsutural cord, but slightly closer to periphery; interval between subsutural and supraperipheral cords a broad, bevelled slope, almost flat, with 2–3 secondary cords developing close to subsutural cord; axial sculpture of bevelled slope comprising low, indistinct axial pliculae (sometimes reduced to faint growth-lines only), but more distinct and more close-set immediately prior to outer lip; interval between supraperipheral cord and periphery distinctly concave, mostly smooth, but additional spiral lirae may develop in last half whorl; periphery strongly angled, crested by 2–3 fine spiral lirae. Base with additional low spiral cords below periphery, but its mid-region smooth or with only incised striae between low broad cords; peri-umbilical region with 2–3 strong cords, innermost of which delineates angular umbilical rim; cords pleated or beaded by distinct radiating pliculae; umbilicus relatively broad (±0.30 of maximum shell diameter) with steep-sided walls bearing fine spiral lirae; funicle lacking. Aperture obliquely D-shaped, peristome interrupted in parietal region; columella pillar slightly thickened, its inner portion with micropustular surface; parietal callus not conspicuously thickened; outer lip descending below periphery immediately prior to insertion, its interior somewhat thickened and sometimes with traces of pustules and 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; largest individuals may exhibit a similar varix-like swelling at ± 0.3 whorl behind outer lip ( Fig. 63E ).

COLOUR. Shell glossy throughout; ground colour whitish, sometimes with a faint pink tinge; colour pattern comprising bright yellowish blotches below suture and at periphery, the two sometimes joined to form axial flames; sometimes also with larger grey-brown blotches; spiral cords with opaque white dots and dashes; base with radiating nacreous or pale brownish blotches separated by white ground colour, peri-umbilical region sometimes with thin, pale brown spiral line; cord at umbilical rim white; apical whorls translucent whitish to pale greyish-white (rarely pinkish), first whorl with a row of opaque white dots at shoulder ( Fig. 63I ); apical bulb of protoconch opaque white. In specimens from the Solomon Islands the ground colour may have a more distinct pale pinkish wash ( Fig. 63G–H ).

DIMENSIONS. Holotype, height 3.0 mm, diameter 5.9 mm; largest specimen, diameter 6.5 mm.

PROTOCONCH ( Fig. 64B ). Typically umboniine, diameter ± 195–210 µm; apical beak present and confluent with terminal lip; apical bulb mostly worn, but with traces of an irregular network of fine threads; terminal lip weakly convex and slightly thickened.

OPERCULUM ( Fig. 64C–D ). Corneous; multispiral; peripheral fringe radially striate; radial striations remaining where whorls overlap; surface with distinct spiral microsculpture.

RADULA ( Fig. 64E–F ). Formula ∞ +(1) +5 +1+5 +(1) +∞, with 30–35 transverse rows of teeth; teeth of central field reduced, but base-plates remaining moderately robust; rachidian base-plate broad, roundly quadrate; base-plates of lateral teeth progressively more trigonal, expanded and bluntly rounded basally, extensively overlapping and with outer anterior edge somewhat raised; fifth lateral more quadrate. Innermost marginal transitional, base-plate robust, shaft reduced, cusp with approx. 5 small denticles of similar size; second marginal clearly the largest tooth, with robust cusp bearing large triangular central denticle with 3–5 smaller denticles at its base on each side; cusps of subsequent marginals similar, but progressively smaller and more finely denticulate.

EXTERNAL ANATOMY (from rehydrated specimen). Head with distinct forehead between cephalic tentacles; snout moderately long, cylindrical, distally papillate; 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; epipodial tentacles micropapillate, number on each side not determined, epipodial sense organs evident; propodium indented in mid-line with a lateral propodial lobe on each side; foot flattened with broad sole, tapering posteriorly. Head-foot translucent cream-white with some opaque white pigmentation on snout, eyestalks, propodial lobes, sides of foot and metapodium.

Habitat

Living specimens at depths of 268–307 m (empty shells 268–343 m); details of substratum not recorded.

Distribution ( Fig. 65 )

Known from the northern Lord Howe Ridge to New Caledonia and the Solomon Islands.

Remarks

Resembles Tylorhaphe wallacei gen. et sp. nov., but lacks the finely beaded, reticulate sculpture, thickened and extended parietal callus lobe and narrow alternating axial colour pattern of that species. In addition, the periphery of T. luteopicta gen. et sp. nov. is more distinctly keeled, the interval between the periphery and supraperipheral cord is smooth and more concave, and the umbilicus is broader (± 0.30 vs 0.22 of maximum shell diameter) and its rim is less overhanging.

Figures

Fig. 63. Tylorhaphe luteopicta gen. et sp. nov. A–D. Holotype, Île des Pins, Stn CP4688, height 3.0 mm, diameter 5.9 mm (MNHN-IM-2000-38874). E. Specimen with additional varix ± 0.3 whorl behind outer lip, Île des Pins, Stn CP4674, diameter 6.3 mm (paratype, MNHN-IM-2000-38876). F. Elevated specimen, Chesterfield Plateau, Stn DW5047, height 3.4 mm, diameter 5.4 mm (paratype, MNHN-IM-2000-38875). G–I. Solomon Islands specimen with slightly pinkish tint, Stn DW1768, diameter 6.0 mm (paratype, MNHN-IM-2000-38877), scale bar =250 µm.

Fig. 64. Tylorhaphe luteopicta gen. et sp. nov. A. Oblique view of apical whorls. B. Protoconch. C. Operculum. D. Detail of operculum showing microscopic spiral sculpture. E. Radula, half row. F. Radula, latero-marginal transition. A–B. Solomon Islands, north of Malaita, Stn DW1768 (paratype, MNHN-IM-2000-38877). C–F. New Caledonia, south of Île des Pins, Stn CP4674 (paratype, MNHN- IM-2000-38876). Scale bars: A=1.0 mm; B, E =50 µm; C=0.5 mm; D= 100 µm; F =20 µm.

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.