Sericominolia porcata, 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 : 65-66

Sericominolia porcata sp. nov.

urn:lsid:zoobank.org:act:4B02E408-3872-43A8-A336-1129B0323038

Figs 29–31

Diagnosis

Shell thin, small, spire low with distinctly shouldered whorls; umbilicus moderately broad, lacking funicle; sculpture of fine, close-set, spiral lirae; early whorls with low, broad axial ridges that render shoulder undulant; ridges evanesce during third whorl; later whorls with fine regular, close-set, collabral pliculae; umbilical rim at most weakly crenulated by growth-lines. Finely mottled in pastel shades and with white-flecked capillary lines.

Etymology

From the Latin ‘ porca ’ f. – a ridge between furrows, and ‘ porcatus ’ – ridged; in reference to the radially ridged sculpture of the apical whorls.

Material examined

Holotype ( Fig. 29 )

NEW CALEDONIA – Loyalty Islands • living specimen; Lifou, Baie du Santal, south of Cap Lefèvre [= Nem], Stn 1454; 20°56.6′ S, 167°02′ E; depth 15–18 m; 23 Nov. 2000; Atelier LIFOU 2000 leg.; tombant sciaphile; MNHN-IM-2000-38848.

Paratypes

NEW CALEDONIA – Loyalty Islands • 2 specimens, living; same data as for holotype; MNHN- IM-2000-38849 • 1 specimen, juvenile, living; Lifou, Baie du Santal, between Cap Wekutr and Cap Wajez, Stn 1455; 20°56.8′ S, 167°02.7′ E; depth 12–20 m; 25 Nov. 2000; Atelier LIFOU 2000 leg.; tombant; MNHN-IM-2000-38850 .

Other material

NEW CALEDONIA – Loyalty Islands • 1 specimen, dead; Lifou, Baie du Santal, W of Pointe d’Easo, Stn 1451; 20°47.3′ S, 167°06.8′ E; depth 10–21 m; 19 Nov. 2000; Atelier LIFOU 2000 leg.; 2 ème patate corallienne; MNHN .

Description ( Fig. 29 )

SHELL. Thin, small (largest specimen, diameter 5.6 mm), wider than high (H/D ±0.64); spire low with stepped profile; periphery at mid-whorl, rounded or weakly angled; spire whorls distinctly shouldered; sculpture fine, predominantly spiral; base shallowly rounded with moderately broad umbilicus; teleoconch of up to 4.25 whorls. First teleoconch whorl bearing three crisp spiral lirae, with broad, widely-spaced, axial ridges developing toward end of whorl; middle lira strongest and forming shoulder at start of second whorl; lirae more numerous and ridges stronger thereafter, rendering shoulder undulant ( Fig. 30A ); whorls flattened above shoulder and flat-sided or weakly concave below it; axial ridges evanesce during third whorl and shoulder more rounded; later whorls more evenly rounded with sculpture of low, close-set, spiral lirae, finer below suture; axial sculpture (in addition to ridges) initially comprising weak, close-set, microscopic threads only, later whorls with fine, regular, close-set, collabral pliculae and stronger, more widely-spaced growth-lines; basal sculpture of broad, flat-topped spiral lirae separated by narrow incised striae, axial pliculae much less distinct; lirae more close-set within umbilicus; umbilical rim rounded and slightly thickened, at most weakly crenulated by growth-lines; umbilicus steep-sided within, lacking a discernible funicle. Aperture roundly quadrate; peristome interrupted in parietal region; columella lip thickened at termination of umbilical rim, its surface microscopically granular; outer lip simple; interior smooth and weakly nacreous.

COLOUR. Pattern of white-flecked spiral capillary lines on a translucent, pale greyish, pinkish-brown or greenish ground with pinkish iridescence; shoulder of spire whorls with radiating white lines, often in pairs ( Fig. 29E ); umbilicus white, holotype with a trace of a yellowish band in umbilicus; protoconch white.

DIMENSIONS. Holotype, height 3.6 mm, diameter 5.6 mm (= largest specimen).

PROTOCONCH ( Fig. 30B ). As in S. lifuana , diameter ± 170 µm.

OPERCULUM. As in S. lifuana .

Habitat

Near-shore, non-lagoonal habitats, at depths of 15–18 m (living specimens the same).

Distribution ( Fig. 31 )

Known only from the Santal Bay area, NW Lifou, Loyalty Islands.

Remarks

The low spire with shouldered whorls and undulant apical sculpture render Sericominolia porcata sp. nov. distinctive. Although some specimens referred to S. lifuana may show traces of such apical undulations, they are more elevated and have a distinct umbilical funicle. In all probability the available material comprises only juvenile and subadult specimens.

Figures

Fig. 29. Sericominolia porcata sp. nov. A–D. Holotype, Lifou, Loyalty Islands, Stn 1454, height 3.6 mm, diameter 5.6 mm (MNHN-IM-2000-38848). E. Close-up of apical whorls, holotype, scale bar =1.0 mm.

Fig. 30. Sericominolia porcata sp. nov., Lifou, Stn 1455 (paratype, MNHN-IM-2000-38850). A. Apical view of early spire whorls showing undulant sculpture. B. Protoconch. Scale bars:A=250 µm; B=50 µm.

Fig. 31. Map of the Loyalty Islands showing distribution of Sericominolia porcata sp. nov. Type locality indicated in pink.