Taxonomic revision of the subterranean genus Virpazaria Gittenberger, 1969 (Gastropoda, Spelaeodiscidae)

. Virpazaria Gittenberger, 1969 is distributed in the Balkan Peninsula (Albania, Montenegro and Croatia) and inhabits the shallow subterranean habitat (MSS) on limestone base rock. Reviewing historical and recently collected material, two species, Virpazaria (Virpazaria) gittenbergeri Fehér & Erőss sp. nov. and Virpazaria (Virpazaria) pesici Fehér & Deli sp. nov., are introduced as new to science. The conservation status of the new species are assessed using IUCN criteria. Two taxa, Virpazaria (Virpazaria) pageti alexanderi Reischütz & Subai, 2012 and Virpazaria (Aemiliella) ripkeni pastorpueri Reischütz et al. , 2011, are synonymized with their nominate subspecies. Some new distribution records, as well as geological and geomorphological data about the known locations for Virpazaria , are presented.


Introduction
Virpazaria Gittenberger, 1969 is a subterranean land snail genus occurring around the transboundary Lake Skadar (in Albania and Montenegro) as well as in the northern part of Kotor Bay (in Montenegro

Material and methods
The new samples were collected between 2015 and 2018.Sampling was done using the ʻscratch & flotate' approach.First, we looked for superficial fissures, cracks and holes in limestone cliffs from where it was possible to scratch out fine granulate material by applying long and narrow handrakes.Shells were then separated by flotation in water.
For non-type material listed in the ʻMaterial examined' sections, the number of specimens in each lot is not generally specified, as there is often uncertainty regarding how the specimens from a collecting event have been distributed between official institutions and the private collections of the collectors.
Albanian and former Yugoslavian geological maps (MMKS 1983;Mikinčić 1953) were used to identify the types and ages of the bedrock at the georeferenced sites.
Digital pictures were made using a Nikon DS-Ri2 camera attached to a Nikon SMZ25 stereo microscope and then combined into focus stack images with Nikon's NIS software.ImageJ 1.49 scientific image analyzing software (Schneider et al. 2012) was used for measurements.We measured shell height, shell width, aperture height and aperture width (see Páll-Gergely et al. 2018: fig. 1), and counted the number of ribs on the last whorl, as well as the number of whorls (± 0.25) according to Kerney & Cameron (1979: 13).

Diagnosis
Shell discoid, dextral, ribbed, colourless (weathered specimens are opaque white), peristome attached, thickened, usually with knob-or tooth-like prominences on palatal and/or basal sides.Peristome insertions are connected; this parietal connection varies from a swollen bulge to a lamelliform flap; in some species this flap might cover a significant part of the aperture in frontal view.Aperture somewhat narrow and moon-shaped.

Remarks
According to Gittenberger (1969Gittenberger ( , 1975) ) as well as Reischütz & Reischütz (2009), Virpazaria is distinguished from the conchologically similar genus Spelaeodiscus by the continuous peristome, i.e., the presence of a parietal bulge or flap that connects the peristome insertions.Spelaeodiscus virpazarioides Páll-Gergely & Fehér, 2018 also possesses a callous parietal structure, but it is much smaller in proportion to the size of the whole aperture.Also, the narrower, crescent-shaped aperture is a good feature to tell Virpazaria apart from related genera.
Due to their hidden life, in most of the cases only empty shells are found.So far, there is one reported case when Virpazaria, more specifically two individuals of V. deelemanorum, were found alive (Gittenberger 1975).Having no pigmented eyes, they are presumably blind, as is usual for subterranean animals.
Comparing their genitals to those of Spelaeodiscus, Klemmia and Aspasita Westerlund, 1889 (Bole 1965;Hudec 1965;Gittenberger 1975;Subai & Dedov 2008), one might discover differences in terms of proportional lengths of certain reproductive organs, and there are certain structures that are called differently by different authors (e.g., the same short protrusion at the border of penis and epiphallus is referred to as flagellum by Gittenberger (1975) and penial caecum by Schileyko (1998)).However, the overall arrangement of the genitalia is similar in these four genera, and no genus-specific differences could be found on the basis of the available literature.
A key to species of Virpazaria 1. Two lamellae, one palatal and one basal, reach deeply (more than 1/10 of whorl) into the aperture .

Distribution
This is the most frequent species of the genus.Its range is northwest of Lake Skadar in Montenegro.

Distribution
This species has a very restricted range west of Lake Shkodër at the foot of the Rumija Mountains in Montenegro (Reischütz & Reischütz 2009;Subai 2009).Apart from the type locality there is another literature record, namely "Ðuravci, 10 km to Ostros" (Subai 2009).None of the published distribution records were georeferenced; thus, it is difficult to say how far these locations are from one another.The site where we found this species is likely identical to, or very close to, the type locality and its bedrock type is Upper-Middle Jurassic limestone.At all three sites, this species was reported to co-occur with V. stojaspali (Fig. 2).Gittenberger, 1969 Fig. 1G-L Virpazaria (Virpazaria) backhuysi Gittenberger, 1969: 299-301, fig. 5.

Diagnosis
Small, discoid and shouldered shell, low but raised spire, wide umbilicus.Callous thickening along entire basal peristome, a smaller knob on palatal peristome.High and thick parietal flap reaching almost up to angular junction.Aperture crescent-shaped, all of it but the sinus region covered by a parietal flap in frontal view.

Distribution
Only the holotype specimen is known, which came from the Edlauer Collection and was probably collected in the 1930s.On the label only "Virpazar Cp.360" is stated.Virpazar is a small historical town with a fortress.In past decades, various malacologists have sampled in and around Virpazar, including E. Gittenberger, H. Nordsieck, A. and P.L. Reischütz, P. Subai and the authors of the present paper, but no one has been able to refind this enigmatic species.This either means that V. backhuysi has a very narrow range and/or is a locally very rare species, or that we searched in all the wrong places.In case of old museum material, the possibility of a past mix-up can never be excluded (see also the doubt regarding the real origin of the type series of V. ripkeni), but it is also feasible that the label information refers to the area around Virpazar in a broader sense.Due to this uncertainty we cannot conclude anything about its preferred bedrock type.Gittenberger, 1975 Virpazaria (Virpazaria) deelemanorum Gittenberger, 1975: 268-269, figs 3 (shell), 4-5 (genitals), table I.1.

Diagnosis
Discoid shell, hardly emerging spire, body whorl silhouette symmetrically rounded.Wide umbilicus.Aperture crescent-shaped, mostly visible in frontal view.Two -more or less equal-sized -knobs on palatal peristome.Callous thickening on peristome between its columellar junction and upper palatal knob.Reischütz et al., 2010 Fig. 3A Gittenberger (2015) mentioned that the protoconch of V. d. dhorai is coarsely granular and that the teleoconch has some irregular radial lines and a very fine microsculpture of incised spiral lines.This, however, is discernible on fresh specimens.Only a few specimens of the nominate form (the types) are known and all are too weathered to observe anything about their shell microsculpture; it is also difficult to conclude whether it is a consistent feature that the palatal knobs are equal-sized in the nominate form.Gittenberger (2015) was somewhat uncertain about the systematic position of the two taxa, but due to the limited amount of material of V. d. deelemanorum, he kept them as subspecies.

Distribution
The range of this species can be found east-northeast of the Shkodër Basin (Albania and Montenegro) (Gittenberger 1975).The nominate subspecies is known from two locations at Mt Fundina (northeast of Podgorica in Montenegro), ca 5-6 km from each other, namely Pecina Cafa Pesatica and Pecina od Zavora near Peuta.The subspecies dhorai was found east of the Shkodër Basin, in Bogë Valley near Xhajë and in the Kiri River Valley near Drisht.The newly discovered latter site extends the known range of this species southwards and indicates that further research in this area might reveal additional locations and a larger range.

Differential diagnosis
This species can be distinguished from congeners by its small size and by its having one knob on the palatal peristome, and from species of the related Spelaeodiscus, which have one knob/tooth on the peristome by its inferiorly broader rounded body whorl and narrower aperture.

Etymology
This species is dedicated to and named after Edmund Gittenberger (Leiden, the Netherlands), a prominent malacologist who did pioneering work on the subterranean terrestrial gastropods of the Balkans.The name is used as the genitive of a noun of male gender.

Description
Shell discoid, spire barely raised, consists of 4¼-4¾ regularly increasing whorls, of which 1½-2 are protoconch whorls.Fresh shells glassy translucent, older shells whitish.Protoconch grained.Teleoconch whorls equidistantly ribbed: 59-69 ribs on body whorl and fine, regular lines in between.In bottom view, umbilicus wide, 1/4-1/ 5 of total shell width, a small part of it overlaid by columellar part of aperture.In frontal view, silhouette of body whorl asymmetrically rounded (shouldered): broader curved in bottom, more angulated on upper side and near suture horizontally flattened.Suture barely depressed.Aperture narrow crescent-shaped.Instead of a flap, with an outstretched swelling (a thickened and emerged callus) on parietal side.One knob on palatal peristome, ca at one-third of way between its angular and columellar junctions.Peristome somewhat reflected between columellar junction and palatal knob, appearing thickened in frontal view.Above knob, peristome simple, delineating an apertural sinus.In side view, parietal swelling oblique (inferior part stands forward) and aperture sigmoidally inclined (inferior part stands backward).

Distribution
This species is known from the southeastern part of the Rumija Mts (also known as Mt Tarabosh).The Štegvaš Pass (Montenegro) and Vallas (Albania) populations are within a distance of 5 km of one another.Both sites are on Upper-Middle Triassic limestone.At the type locality, this species was found together with V. stojaspali and V. pesici.

Conservation status
To our present knowledge, this is a narrow-range endemic species with an area of occurrence (AOO) smaller than 20 km 2 .However, there is no reason to suppose that AOO, extent of occurrence (EOO), number of locations, number of subpopulations or the number of mature individuals are declining or extremely fluctuating.Therefore, it might be assessed as Near Threatened (NT).

Diagnosis
Small, shouldered, low conical shell, with conically raised spire, moderately wide umbilicus.Aperture crescent-shaped, most of it apart from sinus region covered by a strong, prominent parietal flap in frontal view.Callous thickening on peristome with a high palatal tooth, very strong basal tooth and an additional lower callous denticle between basal tooth and columellar insertion of peristome.

Diagnosis
Distinguished from nominate form by smaller, non-detached aperture, which is less covered by parietal flap in frontal view.

Distribution and remarks
This species (including its subspecies) has a restricted range north of Kotor Bay in Croatia and Montenegro (Gittenberger 1969;Reischütz et al. 2012).The type lot of the nominate form was collected from debris at the mouth of the Sutorina River.Later, this species was found in rock crevices at the eastern side of Prevlaka Peninsula, between Njivice and Igalo very near the type locality (see Gittenberger 1988).At another point of the Prevlaka, ca 3.5 km as the crow flies from the former site, Reischütz et al. (2012) reported further shells of this species (four adults and 15 juveniles).They were distinguished from the nominate form by their smaller shell, finer and denser ribbing, smaller parietal flap, as well as the nondetached aperture, and were described as Virpazaria pageti alexanderi.In 2018, we were able to obtain a larger sample of V. p. alexanderi from the type locality that provided a good opportunity to study size extremes and the variability of character states within this population.In our sample (HNHM 104391), shell width ranged between 2.1 and 3.0 mm, shell height between 1.3 and 1.9 mm, number of whorls between 3¾ and 4¼, number of ribs on the last whorl between 48 and 83 and we found specimens with detached and non-detached apertures as well.The values and character states given by Gittenberger (1988) for the nominate form and those given by Reischütz et al. (2012) for V. p. alexanderi all fall within these ranges.This alone might be a good reason for treating them as synonyms, which is only reinforced once their geographical distribution is also taken into consideration.The two type localities are not only close to each other, but are located along the foot of the same limestone hill, which is composed of the same Upper Cretaceous geological formation.Having no geographical or geological barrier in between, it is likely that the two sites contain the same subterranean population and an extensive sampling along the Prevlaka Peninsula might detect this species at further locations.
Virpazaria pageti kleteckii was found at two locations somewhat north of the Prevlaka; namely at Vilina Spilja near Gruda and at Dubravka ca 5 km NE of Gruda.The original description was based on four specimens only (three from Vilina Spilja and one from Dubravka).Until further available material makes it possible to test the stability of distinguishing features, V. p. kleteckii must be accepted as a distinct subspecies.Fehér & Deli sp. nov. urn:lsid:zoobank.org:act

Differential diagnosis
This species can be distinguished from all congeners by its large size; additionally, from V. deelemanorum, which also has two knobs on the peristome, by the smaller knobs and more reduced parietal flap; from Spelaeodiscus unidentatus Bole, 1961 andS. albanicus (A.J. Wagner, 1914), which have small knobs on their peristome, by the crescent-shaped aperture and the presence of a parietal flap.

Etymology
This species is dedicated to and named after Vladimir Pešić (Podgorica, Montenegro) a prominent acarologist and hydrobiologist who significantly contributed to our knowledge of the mollusc fauna of Montenegro.The name is used as the genitive of a noun of male gender.
In bottom view, umbilicus wide, ¼ of total shell width, a small part of it overlayed by columellar part of aperture.In frontal view, silhouette of body whorl more or less regularly rounded: bottom side slightly broader curved.Suture slightly but perceptibly depressed.Aperture crescent-shaped, parietal flap small, thin and weakly attached to shell (often missing from weathered old shells).Two knobs on peristome: a wider basal and a higher (rather tooth-like) palatal.Palatal knob situated somewhat lower than one-third way between angular and columellar junctions of peristome.Peristome somewhat reflected between columellar junction and palatal knob, appearing thickened in frontal view.Above palatal knob, peristome simple.In side view, parietal flap oblique (inferior part stands forward) and aperture sigmoidally inclined (inferior part stands backward).

Distribution
So far, this species has only been found on the southern side beneath Štegvaš Pass in the Rumija Mts, on Upper-Middle Triassic limestone.It was found there together with V. stojaspali and V. gittenbergeri sp.nov.

Conservation status
To our present knowledge this species is very rare, all known records belonging to the same subpopulation and AOO is smaller than 20 km 2 .At the same time, there is no reason to suppose that AOO, EOO, number of locations, number of subpopulations or the number of mature individuals are declining or extremely fluctuating.Therefore, it might be assessed as Near Threatened (NT).Reischütz et al., 2009 Fig. 3F  Renc Mts site on Upper Cretaceous limestone.If these were the only known localities, this would already make V. ripkeni the widest distributed species of its genus.Strangely, the type locality of the nominate subspecies is located at the northwestern side of the Shkodër Lake Basin, very far from these Albanian sites (but see Remarks).

Remarks
This species was described on the basis of eight specimens.Their width and height are 3.5-4.0mm and 2.05-2.25 mm, respectively, and the number of ribs on the last whorl is 73-86.In the original description (Gittenberger 1969) somewhat lower values were given, probably because he applied a different measuring method.The holotype of V. pastorpueri is 3.6 mm wide and 2.15 mm high with 60 ribs on its last whorl (although Reischütz et al. (2011) provided a smaller width (3.0-3.5 mm), a larger height (2.5 mm) and an average of 65 ribs on the last whorl).Smaller and more tapered shells were defined by Reischütz et al. (2011) as the most important features to distinguish V. pastorpueri from V. ripkeni.Later, Gittenberger (2015) studied a larger series of topotypical V. pastorpueri specimens and concluded that their shells are neither smaller nor relatively higher and thicker discoid than those of typical V. ripkeni.However, he found that the ribbing of V. pastorpueri is less dense (less than 70 ribs on the last whorl) and therefore he preserved it as a distinct subspecies, V. ripkeni pastorpueri.In the same paper, Gittenberger described another subspecies, V. ripkeni arbeni, which is smaller (H 1.7-1.8mm; W 3.0-3.1 mm) and has a weakly developed peristome.
We collected several hundred specimens of this species at four different locations in the Renc Mts.Their shell width ranges between 2.7 and 3.6 mm, shell height between 1.5 and 2.1 mm and the number of ribs on the last whorl between 60 and 82.Compared to topotypical V. pastorpueri, their size, shape and rib density values largely overlap.Although one might say that they are generally somewhat smaller and more tapered than typical V. ripkeni, neither these characters nor the rib density are able to provide a clear-cut distinction.This large variability in rib density refutes Gittenberger's argument (Gittenberger 2015), and makes any distinction between V. pastorpueri and V. ripkeni meaningless.However, none of the many adult specimens from the Renc Mts have such a weakly developed peristome as in the three specimens that were described as V. ripkeni arbeni.Having no more material available from the type locality of V. r. arbeni (Shkodër), it is not possible to test whether the entire population consistently has an underdeveloped peristome there or the subspecies was described on the basis of three freak individuals.Until this question is settled, we must preserve V. ripkeni arbeni.
The type material of V. ripkeni was presumably collected by Petar Dabović in the 1930s, passed somehow to the Viennese private collector Aemilian Edlauer, and finally landed in the NHMW Mollusc Collection.It appears that Edlauer, or someone else who studied his collection, recognized, but never described, three different species of Virpazaria.The proposed names were ʻTrissexodon kuščeriʼ, ʻTrissexodon montenegrinaʼand ʻTrissexodon Käufeliʼ.The latter name was obviously proposed for V. pageti, but the situation is more dubious with the other two.Among the lots of V. adrianae we could find both ʻTrissexodon kuščeriʼ and ʻTrissexodon montenegrina' labels, whereas the name ʻTrissexodon kuščeri' also appears in the material of V. ripkeni.Gittenberger (1969) mentioned eight type specimens of V. ripkeni from the same original lot (of which one was designated as a holotype, one made its way to the RMNH and six remained in the original vial and kept the original labels (NHMW 77153a)).Interestingly, another site, "Pečina Grbočica bei Virpazar", is indicated on the original label in that vial, whereas "Soko Höhle bei Dupilo", which is given in the description, can be found on a newer label written in someone else's handwriting.Furthermore, there is another lot (NHMW 77154), which is from Soko Cave according to the original label and contains one specimen of V. ripkeni, but not mentioned by Gittenberger (1969).Even stranger, this lot contains an original Edlauer label with the same locality, the same voucher number (E-57441) and the same proposed name, ʻTrissexodon kusceri', as the type lot of V. adrianae.It seems very difficult, if not impossible, to trace back whether there was any mixup with the labels or the specimens in the past, and, if so, where exactly the type specimens of V. ripkeni came from (Soko?, Grbočica?or from somewhere else?).The fact that neither Gittenberger (1975) nor anyone else has been able to refind V. ripkeni at its alleged type locality or anywhere else in the Virpazar area further discredits the validity of the type locality.

Discussion
Species of Virpazaria inhabit the karstic hills surrounding the basin of Lake Shkodër and a small isolated spot in the coastal foothills of the Orjen Mts at the northern part of Kotor Bay.This narrow-range genus comprises ten narrow-range species.
In this paper, we describe two of them as new and also propose the synonymization of V. ripkeni pastorpueri and V. pageti alexanderi with their nominate forms.At the time of their description, based on the knowledge at that time, they fulfilled the requirements to consider them subspecies, i.e., they seemed to occupy distinct geographic and they seemed to have distinct morphological character(s).Now, however, available new distribution records and larger samples allow us to see them in a new light.Now we know that the intra-population variability of the features believed to be important for subspecific distinction in V. ripkeni and V. pageti (shell size, shell shape, rib density) is far larger than the interpopulation differences.At the same time, we did not change the status of three other subspecies, namely V. deelemanorum dhorai, V. pageti kleteckii and V. ripkeni arbeni, more because we do not have enough data than because we are convinced of their distinct status.Since the genus Virpazaria is far from well explored, it can be assumed that after more intense sampling, new populations will be discovered and more material will be available in the future.This will hopefully provide a better foundation on which to test and reevaluate the taxonomic status of the three aforementioned subspecies.
Virpazaria is obviously bound to karstic areas, but we could not discover any preference in terms of the type or age of the limestone baserock.Usually, one species of Virpazaria is found at a given location, but there are cases when two or three congeners have been found to co-occur.The associated fauna frequently includes other MSS-specific species of Platyla, Vitrea and Gyralina, and occasionally Pholeotheras euthrix and species of Spelaeodiscus, Klemmia and Agardhiella as well.
Generally speaking, there were two different types of (not always easily distinguishable) micro-habitats where we sampled: (i) holes that are probably terminal caverns, with clearly visible signs of dissolution of the rock by water and (ii) fissures or cracks in the rock formed mechanically and filled with a deposit of particulate matter.At the moment we still have too few data to draw far-reaching conclusions, but we had the impression during our field work that Virpazaria prefers the former, whereas Agardhiella and Spelaeodiscus prefer the latter type of micro-habitat.This might be a potential explanation of why they cannot be found more often syntopically; however, this idea needs to be statistically tested on a larger dataset (as in Fehér et al. 2018).

Fig. 2 .
Fig. 2. Distribution of species of Virpazaria Gittenberger, 1969 in the western part of the Balkan Peninsula.