Checklist of the freshwater snails (Mollusca: Gastropoda) of Mongolia Author Marinskiy, Vadim V. text Zootaxa 2017 2017-01-01 4317 1 45 78 journal article 32235 10.11646/zootaxa.4317.1.2 d9650b33-97b2-4d9c-867b-79cd628daf8f 1175-5326 880022 Cd399D08-1Db1-4319-Aa0D-Db560C7C38Df Gyraulus sibiricus ( Dunker, 1848 ) ( fig. 6 K ) Regional distribution. Since MartenS (1882) Gyraulus sibiricus haS repeatedly been reported from Mongolia and adjacent areaS ( Möllendorff 1901 ; ProzoroVa & StarobogatoV 1997 ; ProzoroVa 2003 ; ProzoroVa et al . 2009). We may report here a Single location of thiS SpecieS, Eter gol RiVer (See Remark below). Extra-limital distribution. The YeniSei RiVer baSin and the RuSSian Far EaSt ( VinarSki & Kantor 2016 ). Remarks. There are SeVeral difficultieS concerned with the determination of the taxonomic identity of G. sibiricus . FirSt of all, the type SerieS iS, probably, loSt. We failed to find it among other SyntypeS from Dunker’S collection kept in ZMB. The original deScription ( Dunker 1848 ) iS too conciSe and iS not accompanied by Shell illuStration. Second, the RuSSian authorS who accept G. sibiricus aS a Valid taxon do not giVe information about the Structure of itS reproductiVe SyStem that iS crucial for Gyraulus SyStematicS ( Meier-Brook 1983 ). At laSt, MartenS (1882) belieVed that G. sibiricus iS a member of the “ Gyraulus albus group”, i.e. it Should exhibit a prominent Spiral Sculpture that iS characteriStic for G. albus and cloSely allied SpecieS ( Meier-Brook 1983 ; StarobogatoV et al. 2004). HoweVer, the ShellS from Mongolia determined by MartenS himSelf aS belonging to G. sibiricus (ZIN) lack any SignS of Such a Sculpture. TABLE 6. Morphometric characteristics of shells of some species of Mongolian planorbid snails*

Shell measUrement / index	Gyraulus chinensis (Nariyn-bUlag spring, n = 40)	Gyraulus kruglowiae (Tolbo Lake, n = 34)	Gyraulus stroemi (floodplain of the TUUl gol River, n = 32)	Helicorbis kozhovi (an oxboW of the Kherlen River, n = 34)
Whorls nUmber	3.50–4.25 3.70±0.19	3.00–4.00 3.41±0.26	3.50–4.25 3.81±0.19	3.00–3.75 3.42±0.22
Shell height (SH), mm	1.4–1.7 1.6±0.1	1.1–1.6 1.3±0.1	1.5–1.8 1.6±0.1	1.1–1.6 1.3±0.1
Shell Width (SW), mm	5.3–6.8 5.8±0.4	3.9–5.5 4.6±0.5	5.6–8.0 6.3±0.5	3.8–4.9 4.4±0.3
ApertUre height (AH)	1.5–2.1 1.8±0.1	1.3–2.1 1.6±0.2	1.4–2.3 1.8±0.5	1.3–1.9 1.6±0.`
ApertUre Width (AW)	1.8–2.5 2.0±0.2	1.6–2.6 2.0±0.2	1.9–2.8 2.2±0.2	1.6–2.4 2.0±0.2
SH/SW	0.24–0.30 0.27±0.02	0.27–0.33 0.30±0.02	0.21–0.29 0.26±0.02	0.27–0.34 0.30±0.02
AH/SH	0.25–0.36 0.31±0.02	0.28–0.41 0.35±0.03	0.25–0.31 0.29±0.02	0.29–0.42 0.36±0.03
AW/AH	0.76–0.95 0.86±0.05	0.68–1.00 0.82±0.07	0.72–0.95 0.81±0.06	0.68–0.89 0.82±0.05

* Above lines—maximum and minimum values; below lines—mean values ± standard deviations. HaVing examined SeVeral Small SampleS of G. sibiricus and G. sibiricus Var. major (MartenS, 1882) from Central ASia (Mongolia, Inner Mongolia, Pamir) determined by MartenS or Möllendorf (ZIN), we found that moSt of theSe ShellS are identical to ShellS of G. chinensis . HoweVer, the ShellS of G. sibiricus Var. major from the Eter gol RiVer (leg. Potanin) look Somewhat different, being more flattened than typical ShellS of G. chinensis (compare figS. 6 I and 6 K). At the Same height, theSe are ViSibly wider that thoSe of G. chinensis . The ratio between Shell height and Shell width (= Shell flatneSS index; SFI hereafter) in SeVeral SpecimenS of G. sibiricus meaSured by uS Varied from 0.21 to 0.24 (the mean Value 0.218), whereaS in G. chinensis thiS ratio iS Significantly higher (See Table 6 ). Since SFI iS a Valuable taxonomic index uSed for delineation of Gyraulus SpecieS ( Meier-Brook 1983 ; Glöer & VinarSki 2009; Aplleton & Miranda 2015 ), we may proViSionally accept here G. sibiricus Var. major aS a taxon diStinct from G. chinensis . Another location of it iS Dzharatay-DabaSu Lake in AlaShan’, Southern Mongolia ( 30.12.1884 , leg. N. PrzewalSki; ZIN). MoSt probably, thiS location iS Situated within current borderS of Inner Mongolia (China).