The genus Diplommatina Benson , 1849 ( Gastropoda : Caenogastropoda : Diplommatinidae ) in Nepal , with the description of seven new species

This paper deals with the taxonomy and faunistics of the genus Diplommatina in Nepal. Altogether 16 species are reported, seven of which are new to science viz. D. abiesiana sp. nov., D. fistulata sp. nov., D. godawariensis sp. nov., D. maipokhariensis sp. nov., D. salgharica sp. nov., D. shivapuriensis sp. nov. and D. syabrubesiensis sp. nov. Information on nine previously reported species is provided: D. exserta Godwin-Austen, 1886, D. folliculus (L. Pfeiffer, 1846), D. miriensis GodwinAusten, 1917,  D.  munipurensis Godwin-Austen, 1892, D. oviformis Fulton, 1901,  D.  pachycheilus Benson, 1857,  D.  regularis  Fulton, 1901, D. silvicola Godwin-Austen, 1886 and D. sperata W.T. Blanford, 1862. Although D. canarica was once reported from Nepal, it is not treated here as it is an endemic of the Western Ghats. A dichotomous identification key for all Nepalese species is presented.


Introduction
created the genus Diplommatina for Bulimus folliculus Pfeiffer, 1846. However, Benson (1849) erroneously placed Diplommatina folliculus in the family Carychiadae (= Carychiidae), because he overlooked the presence of an operculum in this species.Conversely, Gray (1850) did observe the operculum lodged inside the shell and therefore transferred Diplommatina to the Cyclophoridae.L. Pfeiffer (1856) erected the family Diplommatinidae (original spelling was Diplommatinacea) to accommodate the genus Diplommatina.
South Asian diplommatinids are usually described on the basis of external shell characters.The density of radial ribs and features of the apertural and internal lamellar system are considered to be of critical value in recognising subgenera and species (Yamazaki et al. 2013;Liew et al. 2014;Neubert & Bouchet 2015).Yet, the internal shell structures of diplommatinids are well characterized in only a few genera, such as Habeas Simone, 2013(see Simone 2013), Diancta, Moussonia, Palaina (see Neubert & Bouchet 2015) and Benigoma Kuroda, 1928 (see Hwang et al. 2009).Conversely, the internal lamellar system in Himalayan Diplommatina is largely unknown.Hitherto, diplommatinids have been poorly studied in Nepal.Kuznetsov & Schileyko (1997) reported four species of Diplommatina in Nepal, viz.D. canarica Beddome, 1875, D. oviformis Fulton, 1901, D. pachycheilus Benson, 1857and D. sperata W.T. Blanford, 1862, whereas Budha et al. (2015) listed 10 species.The present paper is the first to provide descriptions of Nepalese Diplommatina, with illustrations of their internal lamellar system.As such, it deals with 16 species of Diplommatina currently reported from Nepal, seven of which are new to science.It does not treat D. canarica because this species is endemic to the Western Ghats.It also includes a dichotomous identification key for the Nepalese species.No attempt has been made to assign species to subgenera because the subgeneric classification of Diplommatina is in need of revision.

Material and methods
Specimens and shells were collected from 2006 to 2010 by hand searching and leaf litter sieving in the following areas in Nepal (Fig. 1): (1) Mahakali River corridor and its tributaries in far west Nepal, (2) the Kalingandaki River corridor in western Nepal, (3) Langtang and Shivapuri-Nagarjun National Parks, Phulchowki Hill in the Lalitpur District, Nagarjun Forest in the Kathmandu District and Siddha Cave area in the Tanahun District in central Nepal, and (4) Maipokhari in the Ilam District in eastern Nepal.
All species were identified by their shell characters.In addition to the shell sculpture, the shape of the peristome and the aperture as well as the internal lamellae are important characters to diagnose species.These characters can be easily studied by making shells transparent in gasoline (Vermeulen 1993).However, very fine spiral striations can be easily overlooked in old shells.Parietal lamellae can be observed only after removing the outer wall of the body whorls (i.e., breaking the shell) to expose their internal structure.The internal parietal lamellae of each species were studied by means of SEM images (Fig. 2B).To this end, shells were first cleaned with tap water and a fine camel-hair brush.The palatal lamellae are illustrated in separate drawings made with a stereo microscope.The shell structure terminology and the nomenclature of internal parietal and palatal lamellae used in this paper are given in Fig. 2 and are based on Neubert & Bouchet (2015) (though slightly modified for the palatal lamellae).
Shell height (SH) and shell width (SW) were measured on graph paper under a NIKON stereo microscope.Measurements are given in mm, except for submillimetric measurements, which are approximate based on up and down scale from the midpoint between two lines at 0 and 1 mm.However, for holotypes exact measurements were taken from SEM images.
Diagnoses are provided for all species from Nepal, except for D. pachycheilus, whose presence in Nepal is only known from a single, doubtful literature record (Kuznetsov & Schileyko 1997).Type series and material from the collections in the London Natural History Museum, United Kingdom (NHM) and the Royal Belgian Institute of Natural Sciences, Brussels (RBINS) were studied, photographed and compared.All newly collected material is deposited in the Central Department Zoology Museum of Tribhuvan University (CDZMTU), Kathmandu, Nepal.Permanent mounts of the opercula were photographed with a digital camera attached to a stereo microscope and a PC at the Central Department of Zoology, Tribhuvan University, Kathmandu, Nepal.SEM images were taken at RBINS, Brussels.
-Columellar tooth (Fig. 2A, 2C): a processus of the columellaris visible on the columellar lip in the aperture.-Dorsal fold (Fig. 3C4, 8C4): fold or elevated part at dorsal part of the body whorl towards the aperture.-Penultimate whorl (Fig. 2A): whorl above the body whorl towards the apex.-Tooth and lamella: all internal structures inside the shell are considered as lamella(e), while the term tooth is applied to the processus on the columellar lip visible through the aperture.-Parietal lamella(e) or parietalis (Prt in Fig. 2B): a lamella on the sutural wall inside the shell.
Inner parietal lamella or inner parietalis (Prt1): sutural lamella close to the columellar axis and the columellaris; Outer parietal lamella or outer parietalis (Prt2): sutural lamella further apart from the columellar axis.-Palatal lamella(e) or palatalis (Fig. 2C): internal lamella on the roof of the body whorl close to the aperture.Horizontal palatalis (Hpt): internal lamella on the roof of the body whorl at the columellar side; Vertical palatalis (Vpt): internal lamella on the roof of the body whorl along or near the constriction that runs from the suture to the base.-Peristome (Fig. 2A).Angular edge of the peristome (AeP): the edge between the parietal and palatal sides; Basal edge of the peristome (BeP): the edge between the basal and columellar sides; Columellar edge of the peristome (CeP): the edge between the basal and parietal sides; Parietal edge of the peristome (PeP): the edge between BeP and AeP.

Diagnosis
Height 1.3-8.0mm.Sinistral or dextral; translucent (whitish in general).Protoconch generally smooth without radial ribs, but with evenly distributed minute pits all over.Teleoconch with radial ribs; spiral striation present or absent.Constriction at, near, or far apart from the parietal wall of the aperture.Internally ornamented with parietal and palatal lamellae and a columellaris.Columellar tooth strong, weak or absent.Aperture usually circular.Peristome with two lips.Operculum paucispiral.

Etymology
The species name refers to the habitat of the type locality, i.e., an Abies forest.
Distinct dorsal fold at base of body whorl, running towards the aperture (Fig. 3C4).Spiral striation present.Umbilical perforation visible, but umbilicus seems to be closed by the reflected edge of the columellar lip.Aperture ear-shaped, parietal wall oblique with regard to the coiling axis; peristome with two close lips; inner lip thickened and forming a thick callus over the parietal wall; under high magnification 12-15 highly dense ribs visible between the lips.Operculum paucispiral, corneous, thin, outer surface smooth, inner surface with thick peripheral circular edge.

Etymology
The species name refers to the tube-like structure of the dorsal fold on the body whorl just behind the aperture.

Etymology
The species name refers to the type locality of Maipokhari, one of the Ramsar sites of Nepal.

Material examined
NEPAL

Remarks
Godwin-Austen (1892) gave the type locality as "South of the Barak River, between the Mao villages and Munipur" and noted that "from the number of specimens found, this appears a very abundant species; I never got anything like it in the Khasi Hills to the west".

Remarks
D. oviformis is a highly variable and very distinct species by its constriction far behind the aperture.This variability is illustrated by the following examples: the syntype shell from Darjiling in the NHM figured by Gude (1921: 326, fig. 36) has a nearly rounded parietal lip, whereas the shell figured by Zilch (1953: fig. 125, cotype SMF 105340, Darjiling, Himalaya) shows a slightly tilted parietal lip towards the columellar axis.Moreover, the apical whorls of the Nepalese shells reported here are comparatively wider than in the shells at NHM and RBINS (525545 from Darjeeling).The two lips of the peristome in the paratype at RBINS are closer to each other than in Nepalese shells.Nevertheless, for the time being we refer to the Nepalese shells as D. oviformis because of the typical constriction far behind the aperture.Benson, 1857 Fig. 6 Diplommatina pachycheilus Benson, 1857: 203.

Remarks
The original spelling of the name is 'pachycheilus '. However, Kobelt (1902), Gude (1921), Kuznetsov & Schileyko (1997), Ramakrishna et al. (2010) and Budha et al. (2015) spell it as 'pachychilus'.This is an unjustified emendation and the original spelling is restored here.This species was reported from Nepal by Kuznetsov & Schileyko (1997), but it has been excluded from the identification key because Nepalese material was not available to examine internal lamellae.The Shivapuri-Nagarjun National Park was reported as a new distributional record for this species in Nepal by Budha et al. (2015).However, these records in fact refer to a new species described here, viz.D. fistulata sp.nov.

Remarks
D. regularis is a very distinct species due to its regularly increasing whorls.Many shells with adult size show a single, very thin peristomal lip typical of juvenile shells.Juvenile shells show a more distinct constriction at the columellar margin than the fully grown shells.

Etymology
The species name refers to Salghari in Nepali, meaning Sal tree (Shorea robusta) forest, indicating the habitat from which the species was collected.

Remarks
Diplommatina salgharica sp.nov. is very similar to D. exserta (see Godwin-Austen 1886: pl.49, figs 2, 2a), but is easily distinguished by its less tumid apical whorls and the presence of two parietal teeth.The constriction is nearly at the middle of the parietal lip in D. exserta, i.e., at the right edge of the peristome immediately to the parietal lip of the aperture.Budha & Backeljau sp. nov. urn:lsid:zoobank.org:act

Remarks
Diplommatina silvicola is a very distinct species due to its ovate and transparent shell.

Etymology
The species name refers to the type locality 'Syabrubesi'.

Remarks
The shell of D. syabrubesiensis sp.nov. is similar to that of D. fistulata sp.nov.However, the peristome of D. fistulata sp.nov. is highly tilted towards the left on the inner wall of the parietal lip on the columellar axis, while it is round in D. syabrubesiensis sp.nov.Moreover, D. fistulata sp.nov.has a strong dorsal fold, which is not distinct in D. syabrubesiensis sp.nov and only visible through careful observation (see Fig. 8C4).

Key to the Nepalese Diplommatina species
A key to 15 species of Diplommatina is provided.Two species of Diplommatina (D. canarica and D. pachycheilus) reported by Kuznetsov & Schileyko (1997) were excluded from the key because neither species were found in the present surveys and no Nepalese material was available to examine internal lamellae.Moreover, D. canarica is endemic in the Western Ghats (Raheem et al. 2014).The genus Diplommatina contains highly endemic species.Ramakrishna et al. (2010) listed 66 species from India, 60 (91%) of which are endemic to India and, of these, 95 % are endemic to the Himalaya.The distribution range of Diplommatina in Nepal (Fig. 11) is restricted to the mountainous areas in Central Nepal, with many species (n = 11) between 2000 m and 2500 m, while only three species are reported below 1500 m, and no species below 700 m.None of the diplommatinids were collected along the Mahakali River corridor in far West Nepal or the Kaligandaki River corridor in western Central Nepal.This might be due to the low altitudes (below 500 m) of these survey sites.Grytness & Vetaas (2002) reported similar species diversity patterns of plants in Nepal, with maximum plant species richness steeply increasing with altitude between 1500 m and 2500 m, but decreasing again above 2500 m.Vermeulen (1993) also found a high degree of endemism of Diplommatina species in the mountain areas in Borneo.

Fig. 1 .
Fig.1.Map of the localities and areas surveyed for Diplommatina spp. in Nepal.
= Angular edge of the peristome BeP = Basal edge of the peristome CeP = Columellar edge of the peristome Co = Constriction Hpt = Horizontal palatalis (with Hpt1 for lower, Hpt2 for upper) PeP = Parietal edge of the peristome Prt = Parietalis (with Prt1 for inner parietalis, Prt2 for outer parietalis) SH = Shell height SW = Shell width Vpt = Vertical palatalis (with Vpt1 for left , Vpt2 for right) Wh = Whorls Institutional abbreviations CDZMTU = Central Department Zoology Museum of Tribhuvan University, Nepal NHM or NHMUK = Natural History Museum, London, UK (NHMUK when citing registered specimens) RBINS = Royal Belgian Institute of Natural Sciences, Brussels, Belgium
RemarksDiplommatina folliculus is a very common, abundant and distinct species that can be distinguished from the others by its strong, widely-spaced lips and costulated radial ribs.It is distributed from the western to the eastern Himalaya.The most similar species is D. silvicola Godwin-Austen, 1886 (pl.LXV, figs 3, 3a), but D. folliculus differs by its more slender shell and less distinct columellar tooth.
Kuznetsov & Schileyko (1997)stinct.Umbilicus open.Aperture circular.Peristome with two close lips; under high magnification 6-8 thin ribs seen between the lips; basal columellar lip slightly directed towards the columella.Parietal wall of aperture not reaching the middle of the body whorl.Pegu secernentibus"), butKuznetsov & Schileyko (1997)reported this species from steep rocks in dense bushes in the Solukhumbu District, eastern Nepal.Nepalese shells are thinner than the alleged syntypes in NHM and have much thinner peristomal lips.Nevertheless, we provisionally assign the above Nepalese shells to D. sperata.