Tylorhaphe alisae gen. et sp. nov.

urn:lsid:zoobank.org:act: C1DE0A17-BDCD-4895-A918-27D5E858555B

Figs 57–59

Ethminolia nektonica (non Okutani, 1961) – Poppe et al. 2006: 108, pl. 56 figs 1, 3 (not 4).

Ethminolia impressa (non G. Nevill & H. Nevill, 1869) – Héros et al. 2007: 209.

Diagnosis

Smaller, more elevated and with less angular whorls than both Tylorhaphe luteopicta gen. et sp. nov. and T. wallacei gen. et sp. nov. Umbilicus wider than that of T. fritillaria gen. et sp. nov. and base with radial colour pattern rather than spots.

Etymology

Named for the NO Alis, on board which living specimens of this species were dredged.

Material examined

Holotype (Fig. 57A–D) 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-2000-38867 .

Paratypes NEW CALEDONIA – Grande Terre • 1 specimen, dead; same data as for holotype; MNHN-IM-2000-38868 • 2 specimens, dead; Passe de Touho, Stn 1249; 20°49.0′ S, 165°19.0′ E; depth 80– 140 m; Sep. 1993; Expédition Montrouzier leg.; muddy sand and mud; MNHN-IM-2000-38869 • 2 specimens, living; SW of Île des Pins, Stn DW4708; 22°44.7′ S, 167°21′ E; depth 68–71 m; 17 Aug. 2016; NO Alis -KANACONO leg.; DNA vouchers; MNHN-IM-2013-69254 and -69275 • 1 specimen, dead; same collection data as for preceding; MNHN-IM-2000-38870 .

Other material

NEW CALEDONIA – Grande Terre • 6 specimens, dead; Chenal de la Passe de Koumac, Stn 1314; 20°39.8′ S, 164°15.3′ E; depth 30–63 m; Oct. 1993; Expédition Montrouzier leg.; sable coquillier vaseux; MNHN • 1 specimen, dead; Chenal au NE du Banc de Touho, Stn 1260; 20°44′ S, 165°14′ E; depth 49–59 m; Sep.1993; Expédition Montrouzier leg.; sable coquillier; MNHN .

Description (Fig. 57)

SHELL. Small (diameter up to 5.0 mm), trochiform, relatively solid, spire of moderate height (H/D = 0.65-0.70); teleoconch of up to 4.5 whorls; periphery roundly angled, situated below mid-whorl; suture level with periphery; base somewhat flattened, with moderately wide umbilicus. First teleoconch whorl with three indistinct, rounded spiral cords; upper one strengthens during second whorl becoming shoulder-like; two cords below this, one at mid-whorl, one level with abapical suture; an additional beaded subsutural cord arises during third whorl and shoulder cord weakens (Fig. 58A); additional intermediary cords arise with growth, but subsutural, mid-whorl and peripheral cords remain somewhat stronger; last adult whorl with 6–8 secondary cords between subsutural cord and mid-whorl cord, with finer spiral threads in their intervals; axial sculpture weak, comprising only low subsutural pleats on mid-spire whorls causing beading of subsutural cord, these becoming more irregular and evanescing with growth; microsculpture of axial threads throughout. Base with fine spiral cords, broader and flatter in middle of base, but strengthening around umbilicus; axial sculpture of collabral growth-lines, sinuous below periphery, some strengthening and becoming pleat-like around umbilicus; umbilicus of moderate width, with angled rim delineated by strong cord beaded by radiating pleats; sides of umbilicus steep, sometimes slightly overhung by rim, with 3–4 low spiral cords within; a funicle lacking. Aperture subquadrate; peristome interrupted in parietal region; columella stout, with a low nodule at its base overlying a notch at junction of columella and basal lips; outer lip slightly descendant at full maturity, and with shallow subperipheral concavity; interior of outer lip smooth, somewhat thickened within.

COLOUR. Pattern comprising fine zig-zag axial lines or flames in yellow and white, often with additional bold, brown subsutural blotches; beaded subsutural cord distinctly pinkish in some specimens (Fig. 57F); middle of base with a bold radiating pattern of alternating white and brown or pinkish trigonal marks; peri-umbilical region straw-yellow; interior of umbilicus whitish; protoconch and apical whorls translucent whitish to pale yellow or greyish, shoulder cord often dotted with opaque white spots; early teleoconch whorls sometimes with dark peripheral band (Fig. 57F); moderately glossy throughout.

DIMENSIONS. Holotype, height 2.9 mm, diameter 4.3 mm; largest specimen, diameter 5.0 mm.

PROTOCONCH (Fig. 58B). Somewhat worn, but evidently similar to that of Tylorhaphe luteopicta gen. et sp. nov.; diameter ±200 µm.

OPERCULUM, RADULA AND EXTERNAL ANATOMY. Unknown.

Habitat

Known only from the deeper lagoon channels and passes; living specimens at depths of 68–71 m, empty shells 59– 80 m.

Distribution (Fig. 59)

All material studied was obtained from Grande Terre, but similar specimens from the Philippines are probably conspecific (see Remarks below).

Remarks

My referral of this species to Tylorhaphe gen. nov. is provisional. The only specimens collected alive were preserved for molecular study and I have not been able examine the external anatomy, operculum and radula to establish whether these exhibit features consistent with Tylorhaphe . Though smaller and less depressed than that of T. luteopicta gen. et. sp. nov., the shell of T. alisae gen. et. sp. nov. also has a distinctly beaded subsutural cord, and exhibits the same sculptural ontogeny and umbilical morphology.

Ethaliella rhodomphala is superficially similar, but in that species the whorls have a more evenly rounded profile and lack an enlarged beaded subsutural cord. In T. alisae gen. et. sp. nov. the spiral sculpture is generally coarser, particularly the cords at and just above the periphery, and those surrounding the umbilicus. In addition, the peri-umbilical region is straw-yellow rather than pink and has coarser radiating pleats, and the umbilicus itself has a more strongly angled rim, steeper sides and coarser internal spiral sculpture.

Perhaps the most similar species is Solarium impressum G. Nevill & H. Nevill, 1869 from Sri Lanka, currently referred to Ethminolia Iredale, 1924 sensu lato (lectotype designated by Herbert 1992: 449, figs 11–113). However, that species has a more stepped spire profile with coarser subsutural beading and a more angular periphery. I consider it probable that S. impressum is also referable to Tylorhaphe gen. nov.

The Philippine material identified as Ethminolia nektonica (Okutani, 1961) by Poppe et al. (2006) appears very similar to T. alisae gen. et sp. nov. and is I believe likely to be conspecific, indicating that the species ranges beyond the New Caledonian region.