A new diplommatinid genus and two new species from the Philippines (Gastropoda, Caenogastropoda, Cyclophoroidea)

Abstract A new diplommatinid genus, Luzonocoptis Páll-Gergely & Hunyadi, gen. n. is erected for two new species, Luzonocoptis antenna Páll-Gergely & Hunyadi, sp. n. and L. angulata Páll-Gergely & Hunyadi, sp. n. Both species inhabit the northeastern part of Luzon Island, Philippines. The genus Luzonocoptis gen. n. is mostly characterized by a very slender shell with 14–18 whorls, a strongly expanded peristome, an interrupted, weak columellar lamella, the absence of any additional plicae or lamellae, and a rachidian tooth having five cusps.


Introduction
Diplommatinidae (Caenogastropoda: Cyclophoroidea) are mostly characterized by small shells, a body whorl with a distinctive constriction, and teeth or plicae, which are situated inside the last whorl. This family is widely distributed in eastern and southern Asia, northern Australia, the Pacific islands, and some isolated distributions in South America and Madagascar (Kobelt 1902, Thiele 1929, Wenz 1939, Haas 1961, Simone 2013, Egorov 2013. The Diplommatinidae of the Philippines were mainly described in 12 papers by Otto von Möllendorff (von Möllendorff 1887a, 1887b, 1887c, 1887d, 1888a, 1888b, 1890a, 1890b, 1891, 1893, 1898, Quadras and von Möllendorff 1893-1896. Although many species were described without figures, Zilch (1953) published photos of all known Philippine diplommatinids. For more than a century, since the last description, no information on the Philippine members of this family has been published. Recently, Poppe et al. (2015) described two species of the Diplommatinidae from the Philippines.

Materials and methods
Determination of number of shell whorls (precision to 0.25 whorl) follows Kerney and Cameron (1979: 13). The radulae of two specimens were examined. Individual desiccated bodies were soaked in 2 M KOH solution overnight before extracting the radula, which was preserved in 70 % ethanol. Shells, operculae and radulae were directly observed without coating under a low vacuum SEM (Miniscope TM-1000, Hitachi High-Technologies, Tokyo). Measurements of the shell were taken as follows: shell width diameter of the penultimate whorl perpendicular to coiling axis; shell height length from apical tip to the edge of the basal section of the peristome parallel to coiling axis; aperture height length from upper palatal to basal section of peristome parallel to coiling axis.
The mostly widely used terms were used in the descriptions, with the exception of the following: "post-constriction bay" refers to the widened area just anterior to operculum; "neck region" indicates the part of the body whorl on the opposite ("back") side of the aperture. Diagnosis. Shell sinistral; apex blunt, club-like; shell very slender with 14-18 whorls, rather regularly, finely ribbed; aperture round with a weak columellar lamella visible from standard apertural view; columellar lamella interrupted, its inner, short portion blunt thorn or tubercle-like, situated inside post-constriction bay; other inner plicae and lamellae absent; outer surface of operculum matt, smooth; inner surface with a very slightly elevated arcuate ridge; rachidian tooth with five cusps (central one blunt, larger than other four cusps), marginal teeth with four pointed cusps. Differential diagnosis. Luzonocoptis gen. n. differs from Palaina Semper, 1865 (type species: Diplommatina macgillivrayi Pfeiffer, 1854) by the unique shell shape, the strongly expanded peristome, and most importantly, the presence of a columellar tooth, which continues to a strongly developed lamella (see Yamazaki et al. 2013 andNeubert andBouchet 2013). The most similar diplommatinid genus in terms of shell characters is Hungerfordia. Luzonocoptis gen. n. differs from Hungerfordia by the presence of an interrupted columellar lamella, and the rachidian tooth, which possess five well-developed cusps. In contrast, the columellar lamella of Hungerfordia is not interrupted, and the rachidian tooth is simpler, with a single, or three cusps.

Abbreviations
Etymology. The first part of the name derives from the name of the island (Luzon), where the included new species have been found. The second part ("-coptis") refers to the similarity with Middle American urocoptid taxa in terms of shell size, shape, colour and habitat. Gender feminine.
Type species. Luzonocoptis antenna sp. n. Content. Luzonocoptis antenna sp. n. and L. angulata sp. n. Distribution. This genus is known so far from northeastern Luzon Island. The distance between the type localities of the two species is approximately 34 km in a straight line. 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.

Luzonocoptis antenna
Description of the shell (Figs 1A-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.
Operculum (Figs 2A-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 semitransparent).
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. Type locality. Philippines, Luzon, Cagayan Province, 10 km southeast from Gattaran, Barangay Naddungan, environment of the Ar-Aro Cave, rock wall facing east, 90 m, 18°4.477'N, 121°44.128'E.

Luzonocoptis angulata
Diagnosis. A tall, yellowish, moderately slender diplommatinid with club-shaped apex, widely spaced, sharp ribs on the last whorl, angled lower whorls, strongly expanded peristome that is slightly oblique to the shell axis, and a weak interrupted columellar lamella.
Description of the shell (Figs 1I-P, 2G, I). Shell sinistral, tall, very slender; apex thickened; penultimate whorl wide, body whorl constricted, peristome strongly expanded; whorls 14-15; shell colour overall pale yellow or corneous to light reddish, 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 teleoconch; first whorls of teleoconch with low, irregular growth wrinkles, which gradually change to a scarcely, regularly ribbed surface; some weak spiral striation visible between ribs; ribs are strongest on last whorl, where they are sometimes lamella-like; upper whorls slightly concave or not concave, slowly, rather regularly increasing; constriction very deep, situated between penultimate and last whorl (just behind parietal part of peristome); deep constriction results in formation of a conspicuous post-constriction bay (widened area just anterior to operculum); last whorl conspicuously narrower than preceding whorl; lower 3-4 whorls slightly keeled at their middle; aperture moderately oblique to shell axis, rounded, with a weak columellar lamella visible from standard apertural view; columellar lamella low, interrupted; its inner, separate, elongated tubercle-like part situated inside post-constriction bay; no other plicae or lamellae found; peristome overall strongly expanded but varies from not reflected to slightly reflected; boundary between inner and outer peristome clearly visible due to sharp edge of inner peristome; outer peristome mostly responsible for ex-panded profile of peristome; upper, parietal part of peristome is attached to penultimate whorl, although expanded part extends above penultimate whorl; umbilicus absent.
Operculum. Unknown. Etymology. The specific epithet angulata (Latin: angled) refers to the keeled lower whorls, which distinguishes this species from L. antenna sp. n.
Habitat and distribution. Empty shells were found at the base of 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. antenna sp. n.
Comparisons. See under Luzonocoptis antenna sp. n.

Discussion
Although molecular phylogenetic studies involving numerous species were recently published (Webster et al. 2012, Liew et al. 2014), molecular information is still lacking on some important members of the family, such as the type species of Diplommatina from the southwestern Himalaya and the type species of several other genus-group taxa, mainly from oceanic islands. As a result, we still largely have to rely on morphology-based taxonomy of diplommatinid species. Placing the two new species described herein into any previously established genera would not be possible without strongly affecting the existing generic definitions (Páll-Gergely 2017). Therefore, from a typological perspective, a new genus, Luzonocoptis gen. n. must be introduced for them. The two Luzonocoptis gen. n. species are similar to species of the Palawan endemic genus Hungerfordia (type species: Hungerfordia pelewensis Beddome, 1889) in the rockdwelling lifestyle, the sinistral coiling direction, the absence of parietal and palatal plicae or lamellae, and the low arcuate ridge on the inner surface of the operculum (Yamazaki et al. 2013(Yamazaki et al. , 2015a(Yamazaki et al. , 2015b. Although the slender shell having numerous (14-18) whorls is unique to the two new Luzonocoptis gen. n. species, it is insufficient alone for genus-level distinction from the conchologically diverse Hungerfordia. However, the interrupted columellar lamella, and the rachidian tooth having five well-developed cusps justifies the distinction of the two new species from Hungerfordia species on the genus level.