Luzonocoptis antenna Pall-Gergely & Hunyadi

Pall-Gergely, Barna, Hunyadi, Andras & Asami, Takahiro, 2017, A new diplommatinid genus and two new species from the Philippines (Gastropoda, Caenogastropoda, Cyclophoroidea), ZooKeys 678, pp. 1-10 : 1

Luzonocoptis antenna Pall-Gergely & Hunyadi sp. n. Figures 1 A–H, 2 A–F, H

Type material.

Philippines, Luzon, Cagayan Province, 20 km south-southeast from Baggao, Barangay San Miguel, environment of the Duba Cave, limestone rock wall on the bank of the Pared River, 50 m, 17°49.967'N, 121°56.042'E, leg. Hunyadi, A., 07.01.2014., HNHM 99995 (holotype, H = 9.4 mm, D = 1.7 mm), HNHM 99997 (5 paratypes), HA/166 paratypes, PGB/3 paratypes.

Type locality.

Philippines, Luzon, Cagayan Province, 20 km south-southeast from Baggao, Barangay San Miguel, environment of the Duba Cave, limestone rock wall on the bank of the Pared River, 50 m, 17°49.967'N, 121°56.042'E.

Diagnosis.

A tall, yellowish, very slender diplommatinid with club-shaped apex, dense, low ribs on the last whorl, rounded lower whorls, strongly expanded and reflected peristome that is strongly oblique to the shell axis, and a weak interrupted columellar lamella.

Description of the shell

(Figs 1 A–H, 2F, H). Shell sinistral, tall, very slender; apex thickened; penultimate whorl wide, body whorl constricted, peristome strongly expanded; whorls 16.5-18; shell colour overall pale yellow or corneous, sometimes seemingly darker due to the desiccated body, subtranslucent; protoconch consists of approximately 1.25-1.5 whorls, finely pitted; first whorls of teleoconch conspicuously narrower than protoconch; teleoconch rather regularly, obliquely ribbed with fine spiral striation, which is most conspicuous on lower whorls; ribs straight on upper whorls but become more wavy on last whorl (especially near suture); upper whorls concave, slowly, rather regularly increasing; constriction deep, situated on penultimate whorl; last whorl conspicuously narrower than preceding whorl; lower whorls rounded; aperture strongly oblique to shell axis, rounded, with a weak columellar lamella visible from standard apertural view; columellar lamella low, interrupted, its inner, separate, blunt thorn-like part situated inside post-constriction bay (widened area just anterior to operculum); no other plicae or lamellae found; peristome overall strongly expanded and reflected; boundary between inner and outer peristome clearly visible due to sharp, usually reddish brown edge of inner peristome; outer peristome mostly responsible for expanded profile of peristome; upper, parietal part of peristome free from penultimate whorl; umbilicus absent.

Measurements.

Shell height: 8.7-10.3 mm; shell width: 1.6-1.8 mm; aperture height: 2.2-2.7 mm (n = 6).

Operculum (Figs 2 A–D). Corneous, flat (not concave); outer surface smooth, without any signs of whorls, but with a very thin matt layer; under matt layer glossy; inner surface overall rather smooth, with a very low arcuate ridge on one side, and a low central nipple, which is also visible from outside (because the operculum is semi-transparent).

Radula (Fig. 2E). Radula taenioglossate. Teeth arranged in v-shaped rows, each transverse row with seven teeth (2-1-1-1-2). Rachidian tooth strongly constricted in its middle part, having five cusps (central cusp largest, blunt, other four cusps pointed); inner marginal and two outer marginal teeth have shallower constriction of plates, and are slightly longer and more slender than central tooth; inner marginal teeth with four pointed cusps, third one (counting from the side of rachidian tooth) is largest; outer marginal teeth with four pointed cusps.

Etymology.

The shell shape of this new species (wide aperture, very slender upper whorls, and a club-shaped apex) resembles a radio antenna . The specific epithet antenna to be used as a noun in apposition.

Habitat and distribution.

Living specimens were found on a limestone rock wall. This species is known from the type locality only, which is situated ca. 34 km in a straight line from the type locality of L. angulata sp. n.

Comparisons.

Most sinistral diplommatinids from the Philippines belong to the genera Palaina and Diancta Martens, 1867, and have conical, ovoid, or cylindrical shells. However, most Diplommatina species from the Philippines are dextral, and the very few sinistral species have much lower spire, and triangular or ovoid shell shape ( Zilch 1953). The only similar species in the region is Luzonocoptis angulata sp. n., which differs from L. antenna sp. n. in the following traits: whorls fewer; lower whorls keeled; aperture less oblique to the shell axis; peristome much less reflected; constriction situated approx. half whorl anteriorly (behind the parietal part of the peristome); ribs more widely-spaced on the neck region; inner, separated part of the columellar lamella blunter.