Sinoxychilus melanoleucus gen. nov. &

Wu, Min & Liu, Zhengping, 2019, The first proven oxychilid land snail endemic to China (Eupulmonata, Gastrodontoidea), ZooKeys 870, pp. 33-50 : 37-44

publication ID	https://dx.doi.org/10.3897/zookeys.870.32903
publication LSID	lsid:zoobank.org:pub:64DCA855-CCB3-4DC9-A607-F614750CAC11
persistent identifier	https://treatment.plazi.org/id/93DE6CE3-9077-5525-87BB-0FA5DDAB0AE4
treatment provided by	ZooKeys by Pensoft
scientific name	Sinoxychilus melanoleucus gen. nov. &
status	sp. nov.

Treatment

Sinoxychilus melanoleucus gen. nov. & sp. nov. Figures 1 View Figure 1 , 2 View Figure 2 , 3 View Figure 3 , 4 View Figure 4 , 5 View Figure 5 , 6 View Figure 6 , 7 View Figure 7 , 8 View Figure 8 , 9 View Figure 9 , 10 View Figure 10 , Table 1

Type material.

Holotype, 1 fma (HBUMM08236 specimen-1), Qingchengshan Mt., humid forest, in litter ( Fig. 9 View Figure 9 ); Sichuan Province, China; 30.919N, 103.494E; 24 March 2018; coll. Liu, Zhengping & Ma, Hongwen. Paratypes, 3 fma (HBUMM08236; specimens 2-4) and 2 fully mature empty shells (HBUMM08236; specimens 6, 7), collection data as holotype. One empty shell specimen (HBUMM08236; specimen 5) was broken accidentally after measurement and as a result is not included as a paratype. From each of type specimens with soft parts (HBUMM08236; specimens 1-4) a piece of foot (HBUMM08236a; specimens 1-4) was cut and preserved in 99.7% ethanol at −20 °C.

Description.

Shell ( Figs 2 View Figure 2 , 3 View Figure 3 ). Dextral; clearly depressed; very thin and fragile; opaque. Whorls convex. Suture impressed. Umbilicus moderately wide. Basal-umbilicus transition gentle. Columella arched to oblique. Columellar lip not dilated, never covering umbilicus. Protoconch with intercrossing radial wrinkles and spiral grooves ( Fig. 3A View Figure 3 ). Teleoconch with regularly, densely distributed spiral furrows ( Fig. 3B View Figure 3 ). Growth lines fine, distinct. Aperture large, oblique, somewhat sinuate at peristome. Body whorl straight. Adult shell neither hairy nor scaly. Body whorl of adult shell very bluntly angulate at periphery, with base convex. Aperture toothless, unexpanded. Peristome rather thin. Callus indistinct. Shell in uniformly greenish yellow, spiral band absent ( Fig. 2 View Figure 2 ). Measurements (n = 6): shell height = 6.7-8.1 (7.7 ± 0.55) mm, shell breadth = 12.6-13.8 (13.2 ± 0.51) mm, aperture height = 4.9-5.7 (5.3 ± 0.31) mm, aperture width = 2.2-2.6 (2.4 ± 0.16) mm, embryonic shell whorls = 1.38-1.63 (1.50 ± 0.079) mm, whorls = 4.25-4.63 (4.41 ± 0.151) mm, shell height/breadth ratio = 0.53-0.62 (0.58 ± 0.030) mm.

General anatomy. Sole tripartite. Caudal foss or caudal horn absent. Eversible head wart between ommatophore insertions absent. Tentacles and dorsum leaden-black. After preservation in 70% ethanol, black pigments on animal become faint. Lower sides and sole creamy white ( Figs 4A View Figure 4 , 10 View Figure 10 ). Jaw oxygnathous, with an evidently median projection ( Fig. 4B View Figure 4 ).

Genitalia ( Figs 4C View Figure 4 , 5 View Figure 5 , 6 View Figure 6 ). Penis sheath about half length of penis, in holotype and two paratypes wrapping about 1/3 central epiphallus ( Figs 4C View Figure 4 , 6 View Figure 6 ), but in one specimen (HBUMM08236; specimen 2) median part of epiphallus loosely joined to distal penis sheath by connective tissue ( Fig. 5A View Figure 5 ). Penis more or less long, moderately thick, surface simple. Sarcobelum absent. Penial caecum present ( Figs 4C View Figure 4 , 5A View Figure 5 , 5B View Figure 5 , 6 View Figure 6 ), having no ex ternal demarcation between it and penis ( Figs 4C View Figure 4 , 5A View Figure 5 , 6 View Figure 6 ). Penial retractor muscle inserting on top of penial caecum. Flagellum absent. Epiphallus thin, but 2-3 times thicker than vas deferens ( Figs 4C View Figure 4 , 5A View Figure 5 , 6 View Figure 6 ). Distal part of epiphallus attached at lateral side of penis by connective tissue before entering it. Penial caecum internally with three pairs of symmetrically arranged low transversal ridges near epiphallic pore which is surrounded by several very fine pilasters ( Fig. 5B View Figure 5 ). Epiphallic papilla absent. Penis internally with a thickened, ‘M’ -shaped median pilaster which has two arms branching into several narrow pilasters and the median pilaster running to the most proximal part of penis where it extends and forming a transversal ridge ( Fig. 5B View Figure 5 ). The ‘M’ -shaped median pilaster consists of connected tubercles, the apex of each bearing a very short spinelet that without exception points to atrium ( Fig. 5C View Figure 5 ). Vagina short, internally simple, without papilla/verge. Perivaginal gland well developed on surface of vagina and proximal part of bursa copulatrix duct ( Figs 4C View Figure 4 , 5A View Figure 5 ). Measurements of holotype: P = 5.0 mm; Ep = 8.4 mm; VD = 6.5 mm; PR = 2.3 mm; Va = 2.3 mm; BC + BCD = 11.8 mm.

Distribution.

The new species is known only from its type locality.

Etymology.

The species is named for the clear demarcation between the leaden black ommatophores and dorsum and the remaining creamy white body, which is reminescent of the giant panda, Ailuropoda melanoleuca by having the color pattern of clear-cut patches of black and white ( Fig. 10 View Figure 10 ).

Ecology.

The new species was found living in extremely humid environment at type locality. In the laboratory, below 100% relative humidity, animals became active at the relatively lower temperature of 5 °C ( Fig. 10 View Figure 10 ) before they were totally inactive at room temperature (ca. 25 °C).

Taxonomic remarks.

This new species can be distinguished from all other Chinese Hyalina species in the measurements of its shells (Table 2) and other features. This species, however, as kindly pointed out by Dr Barna Páll-Gergely, is obviously close to Zonites scrobiculatus Gredler, 1885, which was usually treated as a species in the bradybaenine genus Coccoglypta Pilsbry, 1895 ( Páll-Gergely in press). The species can be promptly distinguished from Z. scrobiculatus , which has two subspecies, namely Z. scrobiculatus scrobiculatus [ Zonites scrobiculatus Gredler, 1885a: 220-221, pl. 6, fig. 2; Tryon 1886: pl. 53, figs 12-14; Bachmann and Gredler 1894: 416 (radula); Retinella? scrobiculata Kobelt 1899: 918, pl. 241, figs 10, 11; Coccoglypta scrobiculata scrobiculata Yen 1939: 153, pl. 15, fig. 62; Coccoglypta scrobiculata Zilch 1974: 211; Coccoglypta (Coccoglypta) scrobiculata scrobiculata Zilch 1968: 180] and Z. scrobiculatus hupeina Gredler, 1887 [ Zonites ( Nanina ?) scrobiculatus var. hupeina Gredler 1887b: 344-345; Coccoglypta scrobiculata hupeina Yen 1939: 153, pl. 15, fig. 63; Zilch 1974: 199; Coccoglypta (Coccoglypta) scrobiculata hupeina Zilch 1968: 180], by having a distinctly smaller shell, with fewer whorls, and a particular shell shape which is sharply divergent from that of Z. scrobiculatus ( Fig. 7 View Figure 7 ). Sinoxychilus melanoleucus is also geographically distant from the geographic range of Z. scrobiculatus ( Fig. 1 View Figure 1 ). Nevertheless, we are inclined to believe that based on shell morphology Z. scrobiculatus should belong to Sinoxychilus , although anatomical and molecular evidence is unavailable.

With respect to the genitalia, Sinoxychilus melanoleucus is similar to the Japanese Urazirochlamys doenitzii (Reinhardt, 1877) ( Helicarionidae sensu Azuma 1995 and Schileyko 2002) in having the apical insertion of penial retractor and the absence of flagellum ( Schileyko 2002: fig. 1600). Sinoxychilus and Urazirochlamys Habe, 1946 also share a characteristically spirally sculptured protoconch. However, the latter genus has a caudal horn ( Azuma 1995: pl. 28, fig. 339), which suggests that Urazirochlamys does not belong to the Oxychilidae .

With the exception of two genera distributed in the southwestern part of the Arabian Peninsula, oxychilid snails are only known from the Western Palearctic ( Neubert 1998; Schileyko 2003). The new species described herein, and its congeners, are undoubtedly the easternmost representatives of Oxychilidae , which suggests that Sinoxychilus might be an isolated group in China, remote from the main distribution area of the family.