Tylorhaphe fritillaria, 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 : 110-113

Tylorhaphe fritillaria gen. et sp. nov.

urn:lsid:zoobank.org:act:0796CFF5-6E23-4D66-A341-5D5729E68949

Figs 60– 62

Diagnosis

Resembles Tylorhaphe alisae gen. et sp. nov., but with a narrower umbilicus, the rim of which conspicuously overhangs the underlying umbilical cavity; rim pleated, but peri-umbilical spiral sculpture lacking; basal colour pattern of numerous white blotches on a pale maroon-brown ground is distinctive.

Etymology

From the Latin ‘ fritillus, fritillaria ’, dice box, spotted; in reference to the spotted colour pattern of the base, reminiscent of that of the flowers of the plant Fritillaria meleagris L. ( Liliaceae ).

Material examined

Holotype ( Fig. 60 )

NEW CALEDONIA – Grande Terre • empty shell; Koumac , Passe Deverd, Stn 1322; 20°45.2′ S, 164°15.2′ E; depth 53–71 m; Oct. 1993; Expédition Montrouzier leg.; sable vaseux; MNHN- IM-2000-38871.

Paratypes

NEW CALEDONIA – Loyalty Islands, Lifou • 3 specimens, dead; Baie du Santal, Récif Shelter, Stn 1461; 20°54′ S, 167°02′ E; depth 100–120 m; 23 Nov. 2000; Atelier LIFOU 2000 leg.; drague; MNHN- IM-2000-38873 .

Description ( Fig. 60 )

SHELL. Small (diameter up to 4.0 mm), trochiform, relatively solid, spire height moderate (H/D = 0.65- 0.75); teleoconch of up to 4.75 whorls; periphery roundly angled, situated close to mid-whorl; suture level with periphery; base relatively narrowly umbilicate. First teleoconch whorl with four fine spiral lirae; two stronger cords develop during second whorl, one at shoulder, the other between this and abapical suture; a third spiral cord arises below adapical suture during third whorl, strengthening and becoming beaded on subsequent whorls; shoulder cord becomes progressively less distinct during fourth whorl and additional spiral lirae develop between cords, particularly between subsutural cord and vestige of shoulder cord; peripheral cord emerges from suture at on last whorl, delineating upper limit of peripheral angulation; whorl profile distinctly concave between peripheral and supraperipheral cords, flatter between supraperipheral and subsutural cords; axial sculpture weak, comprising only indistinct growth-lines, most noticeable in final quarter whorl, microsculpture of axial threads throughout. Base with 3–4 spiral cords below periphery, its mid-region smoother with only collabral growth-lines, sinuous below periphery; peri-umbilical region with strong pleats radiating from umbilical rim, but without spiral sculpture; umbilicus relatively narrow, its rim thickened and roundly angled, crenulated by radiating pleats; sides of umbilicus steep, greatly overhung by umbilical rim, with low spiral cords within; a funicle lacking. Aperture subquadrate; peristome interrupted in parietal region; columella stout, with a low bulge at its base and a shallow notch at end of thickened umbilical rim, at junction of columella and basal lips; outer lip not descendant in material available, shallowly indented below periphery; interior of outer lip smooth, somewhat thickened within.

COLOUR. Pattern variable; ground colour typically whitish, mottled with spots, blotches and lines in shades of brownish-yellow to olive-brown; a spiral band of narrow, alternately white and brownish-yellow axial lines above supraperipheral cord; peripheral cord with small, widely-spaced, maroon-red spots; base with a maroon-brown ground densely spotted with white blotches; umbilical rim and columella whitish. Some specimens more uniformly pale orange above periphery, with pinkish subsutural, shoulder and peripheral cords. Basal ground colour turning rose-pink in older post-mortem specimens.

DIMENSIONS. Holotype, height 2.5 mm, diameter 3.6 mm; largest specimen, diameter 4.0 mm.

PROTOCONCH ( Fig. 61C ). Somewhat worn, but evidently similar to that of Tylorhaphe luteopicta gen. et sp. nov.; diameter ±195 µm.

OPERCULUM, RADULA AND EXTERNAL ANATOMY. Unknown.

Habitat

Known only from off-shore habitats and deeper lagoon channels and passes; at depths of 71–100 m; living specimens unknown.

Distribution ( Fig. 62 )

Known only from New Caledonia (Grande Terre and Loyalty Islands).

Remarks

As with Tylorhaphe alisae gen. et sp. nov., my referral of this species to Tylorhaphe gen. nov. is provisional as data regarding its radula morphology are wanting. However, conchological features, in particular the ontogeny of the spiral sculpture, the strongly beaded subsutural cord, the angular periphery and the morphology of the umbilical region, are consistent with those of Tylorhaphe gen. nov. Its small size, narrow umbilicus without peri-umbilical spiral cords, and distinctive basal colour pattern render it easily separable from other species in the genus. The most similar species, T. alisae , has a broader umbilicus bordered by distinct spiral cords, and its umbilical rim does not overhang the underlying umbilical cavity to the same extent.

Figures

Fig. 60. Tylorhaphe fritillaria gen. et sp. nov. A–D. Holotype, Koumac, Stn 1322, height 2.5 mm, diameter 3.6 mm (MNHN-IM-2000-38871).

Fig. 61. Tylorhaphe fritillaria gen. et sp. nov., Lifou, Stn 1461 (paratype, MNHN-IM-2000-38873). A. Apical view of spire. B. Oblique view of spire, scale bar =0.5 mm. C. Protoconch. Scale bars: A–B =0.5 mm; C =100.

Fig. 62. Map of New Caledonia showing the distribution of Tylorhaphe fritillaria gen. et sp. nov. Type locality indicated in pink.