Sinorachis baihu Wu & Chen

Wu, Min, Chen, Zheyu & Zhang, Liwan, 2019, Jawless land snail Sinorachis, a new bradybaenine genus from China (Eupulmonata, Camaenidae), ZooKeys 893, pp. 51-67 : 51

publication ID	https://dx.doi.org/10.3897/zookeys.893.38445
publication LSID	lsid:zoobank.org:pub:0116CFB3-7952-4E4A-B8D9-A42E4802EE38
persistent identifier	https://treatment.plazi.org/id/257DD29C-258B-5E2B-89E1-76C71C8B3183
treatment provided by	ZooKeys by Pensoft
scientific name	Sinorachis baihu Wu & Chen
status	sp. nov.

Treatment

Sinorachis baihu Wu & Chen sp. nov. Figs 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

Type material.

Holotype: CHINA • fully mature animal; Hubei, Lichuan, Liangwuxiang, Shanchacun; 108.837°E, 30.274°N; 1.XI.2018; Liwan Zhang leg.; HBUMM08296-specimen 1. Paratype: one juvenile animal; same data as for preceding; HBUMM08296-specimen 2. Partial foot was cut off in both specimens and preserved in 99.7% ethanol at -20 °C; HBUMM08296a-specimens 1, 2.

Diagnosis.

Embryonic shell with pits, each having a central hump. Shell with three bands.

Description.

Shell ( Figs 2 View Figure 2 , 6D, E View Figure 6 ). Conical; thin but solid; dextral. Whorls slightly convex. Suture impressed. Umbilicus a slit. Columella almost vertical. Protoconch densely and evenly covered with fine centrally-uplifted pits ( Fig. 6D, E View Figure 6 ). Teleoconch without spiral furrows. Aperture oblique; not sinuate at peristome. Body whorl not descending behind aperture. Shell surface without ribs. Growth lines fine. Adult shell not hairy or scaly. Adult body whorl rounded at periphery; with bottom convex. Ring-like thickening within aperture absent. Peristome thin; not reflexed. Callus thin and transparent. Shell glossy; white. A suture band, a supra-peripheral band and a subperipheral band more or less broken. Measurements (holotype): shell height 14.7 mm, shell breadth 8.7 mm, aperture height 5.3 mm, aperture width 3.5 mm, embryonic shell whorls 1.500, whorls 5.125, shell height/ breadth ratio 1.70.

General anatomy ( Figs 3 View Figure 3 , 4 View Figure 4 ). A crest-like head wart between and slightly behind ommatophore insertions present. On left edge of mantle collar a leaf-shaped appendage present. Body dorsally white; symmetrically with two lateral black pigmented stripes that become lighter near sole. Sole creamy white. Jaw absent ( Fig. 4C, D, G View Figure 4 ).

Pallial complex ( Fig. 5 View Figure 5 ). Pallial roof not pigmented. Pallial gland thin, parallel to mantle collar. Hindgut running parallel to parietal-palatal margin for length of pallial chamber. Ureter slender, typical sigmurethrous, about 1/5 breadth of hindgut, adhering to hindgut for all its length. Secondary ureter developed. Kidney triangular, not bilobed, about as long as 1/2 of pallial chamber. Heart as long as 1/3 - 1/2 of kidney. Main pulmonary vein running along contour and apex of kidney, then diffusing into thinner veins mostly concentrated on anterior half.

Radula ( Fig. 6 A–C View Figure 6 ): Teeth arranged in transversal rows, each row containing about 151 (75-1-75) closely arranged teeth. Central tooth tricuspid, narrowly tongue-shaped ( Fig. 6A View Figure 6 ). Lateral teeth slightly thickened at inner edge; bicuspid (L1-2 or L1-3) ( Fig. 6A View Figure 6 ), tricuspid (from L2 or L3 on) ( Fig. 6A, B View Figure 6 ) and gradually transformed to marginals with one endocone and three or four ectocones ( Fig. 6C View Figure 6 ).

Genital system ( Figs 7 View Figure 7 , 8 View Figure 8 ). Penis sheath long, covering approximately 3/4 of penis. Penis thin; externally simple; internally with three pilasters. Epiphallus subequal to penis in length; without epiphallic papilla. Flagellum absent. Vas deferens ca. 1/2 length of epiphallus; of even thickness. Epiphallus and vas deferens sharply demarcated ( Fig. 7 View Figure 7 ). Dart sac apparatus large in size; distal 1/3 with a distinct accessory sac ventrally that is internally solid. Love dart very short, approximate 0.7 mm long; sharply tapering from distal end; transparent. Mucous gland with one common peduncle; simply branched. Vagina as long as penis. Bursa copulatrix small, ball-shaped.

Measurements of holotype.

DS– 5.9 mm long, 1.5 mm broad; DtC– 0.7 mm; MG– 2.7 mm; P– 7.3 mm; Ep– 7.5 mm; VD– 3.8 mm; PR– 5.5 mm; Va– 5.7 mm; FO– 3.1 mm; BC plus BCD– 5.7 mm.

Etymology.

This species is named after baihu (=白虎in Chinese, means white tiger) which is the totem of the local Tujia people.

Type locality.

Lichuan, only known from the type locality ( Fig. 1 View Figure 1 ).

Distribution.

Hubei.

Ecology.

This species was only found on the trunk of a tree ( Fig. 9A View Figure 9 ).

Taxonomic remarks.

The new species and the two species that were once placed in the genus Rachis share many conchological features. However, typical sigmurethrous pallial complex ( Solem 1985) is observed in the new species. The new species is slightly smaller than and obviously thinner than Sinorachis onychinus (height 16 mm, diam. maj. 11 mm: Heude 1885: 114, pl. 30, fig. 5). The new species can be distinguished from S. onychinus by having evenly distributed pits each centrally with a hump on the embryonic shell. In S. onychinus , the embryonic shell is smooth on the first 0.5 whorl, and is axially wrinkled on the subsequent protoconch whorls (0.5-1.25 whorl). On the remaining embryonic whorls, the sculpture is shown as evenly distributed tiny pits [examined material: SMF42825, SMF42826: Patung, Hupei, Mlldff. G., Slg. Kobelt u. Bttgr. SMF42827: Sinorachis onychinus (not paratypes of Rhachis chalcedonicus as mentioned in Yen 1939: 91, pl. 8, fig. 47), SW Hubei, Gredler G., Slg. Mlldff. SMF1045593] that become weak or disappear altogether.

In pulmonates the presence of a jaw is a ubiquitous characteristic related to herbivorous/ detritivorous/ fungivorous foraging strategies, while the absence of a jaw is correlated with predation/carnivorous foraging strategies ( Mordan and Wade 2008). In addition, the absence of a jaw also occurs in some non-carnivorous groups, such as Achatinellidae , which are fungivorous and have the jaw weakly developed or absent ( Schileyko 1998a). The comparison between the new species and Laeocathaica prionotropis Möllendorff, 1899 ( Bradybaeninae) ( Fig. 6F, G View Figure 6 . HBUMM08299-spec. 1, Bikou, Wenxian, Gansu. Coll. Li, Q., April 2019) indicates they are two different types of radula. The latter species, a typical ground-dweller, is herbivorous snail, which has the robust cone-shaped and sparsely arranged radular teeth that seem to be typical in bradybaenine snails (e.g., compare it with fig. 4 in Páll-Gergely and Hunyadi 2016), while the new species has more slender and densely arranged radular teeth, which suggest the diet range of this species might not cover large plants and animals.