Gastrocoptaarmigerella (Reinhardt, 1877) and Gastrocoptatheeli (Westerlund, 1877) in western Tien Shan, Kyrgyzstan, and their further occurrence in Asia (Mollusca, Gastropoda, Pupilloidea)

Abstract Gastrocoptaarmigerella (Reinhardt, 1877) has been described from Japan and is widespread in the Far East and China. Surprisingly, a few occurrences in central and western Asia have also become known. Forcart (1935) found G.armigerella in northern Iran. The authors found evidence of G.armigerella in western Tien Shan, Kyrgyzstan. The form from northern Tajikistan described by Schileyko (1984) as G.huttoniana agrees morphologically with G.armigerella as well. Gastrocoptahuttoniana is known from western India and the Himalayan region. The evidence of G.armigerella from central and western Asia has come thus far from drift material at the high water line in river floodplains which suggests that these are sub-fossil or fossil shells (Holocene or Pleistocene) which have been relocated. No living example of Gastrocopta has been found there as yet. Possibly the species is now extinct in this region. Gastrocoptatheeli (Westerlund, 1877) is the most widespread Gastrocopta in Eurasia. Its area ranges from the Caucasus to the Far East. The findings reported here are the first for this species in western Tien Shan.


Materials and methods
From the Kara Suu River floodplain in the western Tien Shan near Dshany Dshol (Kyrgyzstan), 860 m a.s.l., 41°35'05.8"N, 072°08'03.3"E, 21.07.1998, leg. S. Meng, the authors have a sample of river drift material from the high water line containing approximately 2000 gastropod shells in total. The genus Gastrocopta is predominant with ~ 430 shells. The Gastrocopta shells are probably all of fossil or sub-fossil origin. Gastrocopta armigerella, G. theeli and G. huttoniana are also evaluated in the bio-geographical context. Additional records of G. theeli in the Siberian Altay and the Far East collected by S. Meng are also included.

Results
Gastrocopta armigerella was found in the drift material from the Kara Suu River floodplain near Dshany Dshol, 860 m a.s.l. (western Tien Shan, Kyrgyzstan). The community as a whole contained mainly elements of the modern thermophilous communities of lowlands and large mountain valleys. The predominant forms were, e.g., Vertigo pygmaea (Draparnaud, 1801), V. antivertigo (Draparnaud, 1801), Truncatellina callicratis (Scacchi, 1833) or Vallonia pulchella (Müller, 1774). The shells of G. armigerella  comprise ~ 20 %, more than 400 shells, of the sample. No remnants of organic material, such as tissue or periostracum were found in any of the G. armigerella specimens. Because of their preservation it is assumed that the shells do not belong to the modern faunal communities and that the material is of Holocene or Late Pleistocene age. Three shells of G. theeli, probably fossils as well, were also found (Fig. 5). This is also a new record for the western Tien Shan. Two fossil or sub-fossil shells of Vallonia zaru Almuhambetova, 1979, a species today restricted as a relict to the northern Tien Shan, were found as well.
Gastrocopta armigerella has five markedly convex whorls. Compared with G. huttoniana and G. theeli, its apertural dentition is very strongly developed (Figs 2-9). Gastrocopta armigerella usually has 7-8 apertural teeth. The angular-parietal lamella has two calluses which are not completely fused. The front tip is inclined towards the palatal wall. An infraparietal (subparietal) callus is present. The columellar tooth forms a strong lamella. The columellar/basal callus is also well developed. There are two palatal lamellae, the lower one of which is more pronounced. In the suprapalatal position there is often a slight thickening of the apertural lip (Reinhardt 1877;Pilsbry 1916Pilsbry -1918Forcart 1935).
In contrast, G. theeli has no infraparietal tooth, the angular-parietal lamella is almost completely fused and three lamellae are found on the palatal wall (Figs 3-5). In general, G. theeli and G. armigerella do not vary much and are relatively stable in their respective shell morphologies.
The Gastrocopta material from northern Tajikistan (Schileyko 1984;Sysoev and Schileyko 2009) corresponds morphologically to G. armigerella, including G. armigerella specimens from western Tien Shan and northern Iran (Forcart 1935) (Fig. 9). The shell sizes (2-2.3 × 1.1-1.2 mm) given by Schileyko (1984) also correspond to the material from western Tien Shan (2.1-2.5 × 1.1-1.2 mm). Since G. armigerella was only found in river drift material and never alive in northern Iran and northern Tajikistan, it must be assumed that this material is also fossil or sub-fossil.
In view of the breadth of its morphological variation, the definition of G. huttoniana is more problematic (Bößneck and Meng 2018). In the lectotype and paralecto- types from Simla in northern India (Raheem et al. 2014: fig. 37A, B), the columellar/ basal callus is much reduced and merely indicated and there is a complete lack of an infraparietal tooth (Fig. 2). However, Pokryszko et al. (2009: 434, fig. 26-28) assumes for the G. huttoniana material from Pakistan that a small infraparietal callus is often present. Forms with an infraparietal callus are also known from Nepal but the systematic status of the material is uncertain (Bößneck and Meng 2018).   Forcart (1935, p. 421), Gastrocopta armigerella masendarensis from Meshhediser (northern Iran) in comparison with Gastrocopta theeli, topotype (shell from type locality Yeniseysk), Senckenberg Museum.
In addition to the evidence of G. theeli in western Tien Shan, the authors can list the following further localities which confirm the main areas of occurrence of the species in the Altay and Far East (Fig.1).

Discussion
The evidence of G. armigerella and G. theeli from the western Tien Shan is of great biogeographic significance. It has confirmed the occurrence of G. armigerella in central and western Asia as well as in the Far East of Russia and in China (Fig. 1). The findings from western Tien Shan constitute an important addition to the findings from northern Iran (Forcart 1935). The evidence from northern Tajikistan also fits into this picture. Although these specimens were identified as G. huttoniana (Schileyko 1984) they clearly correspond morphologically to G. armigerella. Since G. armigerella has so far not been found alive in western and central Asia and it is possible that the shells are subfossil or fossil, it must be assumed that the species has become extinct there. The dating of the shells, e.g. 14 C dating, is problematic because the shells are extremely small. Finding the sediment deposits from which the shells were washed out would allow dating of the material with alternative methods. G. theeli has also not been found alive in western Tien Shan, but its (sub) fossil occurrence fits with the widespread distribution of relict populations of this species from the Caucasus to the Altay and the Far East.
Some forms of G. armigerella which differ slightly in their overall appearance have been described as a subspecies, such as G. a. hachijoensis Pilsbry, 1916 from Japan (Hachijojima, Izu, Hirase), G. a. daitojimana Kuroda, 1960 also from Japan and, as already mentioned, G. a. masenderanensis Forcart, 1935 from northern Iran. These forms cannot be discussed in greater detail here. They probably fall into the synonymy of G. armigerella. Uvalieva (1990) mentioned Gastrocopta gracilidens (Sandberger, 1875) from the Pleistocene and Holocene in central Asia (Kazakhstan and the surrounding area) without more precise primary data and G. huttoniana from the Pleistocene of that area. G. gracilidens is a synonym for G. nouletiana (Dupuy, 1850). G. nouletiana is very similar to G. armigerella, but more compact in appearance and has a larger number of palatal teeth. Moreover, G. nouletiana was widespread in Eurasia in the Miocene approximately 15 million years ago (Steklov 1966: 141, fig. 48;Stworzewicz 1999: 164, fig. 59-61). In the case of G. huttoniana, it is possible that Uvalieva was referring to the description by Schileyko (1984). In conclusion, it must therefore be assumed that there are possibly further occurrences of G. armigerella in central Asia which have merely not yet been interpreted correctly.
Whether G. coreana and G. theeli are synonyms of each other remains an open question. Likewise, it is currently still unclear whether G. armigerella occurs in addition to G. hirasei in Korea. These questions can probably be only solved using molecular methods. In addition, it should be checked whether G. huttoniana, with its variable shell morphology in the Himalayan region, indeed represents a single taxon.