A taxonomic note on the helicoid land snail genus Traumatophora (Eupulmonata, Camaenidae)

Abstract Traumatophoratriscalpta (Martens, 1875) is reported for the first time from the Tianmushan Mountains, Zhejiang Province, and its morpho-anatomy is described based on this new material. The genus Traumatophora is redefined on the basis of both shell and genital anatomy of its type species. The presence of the dart apparatus suggests this genus belongs to the subfamily Bradybaeninae rather than to the Camaeninae. This genus is distinguished from all other Chinese bradybaenine genera by the combination of the following key morphological characteristics: embryonic shell smooth, palatal teeth present, dart sac tiny with rounded proximal accessory sac that opens into a dart sac chamber, mucous glands well developed, entering an accessory sac through a papilla, epiphallic papilla absent, flagellum present. A comparison is also presented of Chinese bradybaenine genera with known terminal genitalia.


Materials and methods
A living specimen was relaxed by drowning in water before being transferred to 70% ethanol for fixation, which was replaced with ethanol of the same concentration after three days. The shell and genitalia were measured with digital vernier callipers (genitalia from photo) to the nearest 0.1 mm. Whorl number was recorded as described by Kerney and Cameron (1979), with 0.125 whorl accuracy. Soft parts were measured after the specimens were sufficiently fixed in 70% ethanol. Directions used in descriptions: proximal = towards the genital atrium; distal = away from the genital atrium.

Systematics
Membranous sac surrounding terminal genitalia absent. Penis sheath absent. Epiphallic papilla wanting. Penial caecum absent. Flagellum present. Dart sac tiny. Accessory sac developed; large; with transversal sphincter muscles. Mucous glands numerous; extremely developed; entering accessory sac by a papilla. A ball-shaped proximal accessory sac with opening leading to dart sac chamber. Poly-layered structure in dart apparatus absent (this study).
Remarks. The genus Traumatophora is transferred herein to the subfamily Bradybaeninae based on the presence of a dart apparatus that is structurally similar to that of other genera in this subfamily. Features typical of the genus include presence of a penis sheath, flagellum, accessory and proximal accessory sac, mucous gland papilla and the absence of an epiphallic papilla, penial caecum, poly-layered structure, and a membranous sac surrounding the terminal genitalia; on this basis the genus Traumatophora is well distinguished from all the other anatomically known Chinese bradybaenine genera [ Table 1; note: at transition of the penis-epiphallus in Acusta (Wu 2004: fig. 18E), Laeocathaica (Wu 2004: fig. B), Eueuhadra (Wu 2004: figs 7B, 7E) and Aegistohadra (Wu 2004: fig. 6C), the structures once called an "epiphallic papilla" are too invisibly tiny (especially compared with those in Pfeifferia Gray, 1853, Pliocathaica Andreae, 1900, etc.) to a true epiphallic papilla. Anatomy information of Armandiella Ancey, 1883 comes from A. sarelii (Martens, 1867) (HBUMM01113 specimen-3, collection information lost)]. However, until now detailed information on the anatomy of the Table 1. Comparison of characteristics of terminal genitalia among Chinese bradybaenine genera (Chang 1990;Wu 2001aWu , 2001bWu and Guo 2003;Schileyko 2004;Wu 2004;Wu and Guo 2006;Wu and Prozorova 2006;Wu and Asami 2017;Páll-Gergely et al. 2018; * this study). AS-accessory sac; DVMmembranous sac surrounding terminal genitalia; EpP-epiphallus papilla; Fl-flagellum; MG-number of mucous gland ducts; MGP-papilla distally leading to mucous glands on inner wall of accessory sac; PAS-proximal accessory sac, a blind sac on proximal dart sac and opening into dart sac chamber or not; PC--penial caecum; PLs--poly-layered structure in dart sac and/or accessory sac, produced by wavy and spongy connective tissue; PS-penis sheath.  General anatomy. Eversible head wart between ommatophore insertions absent. Tentacles and dorsum leaden-black. Sole and the remaining lower lateral side creamy white. Jaw arcuate; with 12 more or less projecting ribs (Fig. 4C).
Ecology. Perhaps this species is among the rarest bradybaenine species in China, although the extant distribution range is large and covers Jiangxi, Hubei, Fujian and Zhejiang. Traumatophora triscalpta was known from higher altitudes of 1200-1500 m (Pilsbry 1890).
Taxonomic remarks. In this study, the Traumatophora specimens from Zhejiang are identified as T. triscalpta based on the original description and comparison of the type material (Fig. 3). I follow Yen (1943) in treating T. triscalpta and T. fraterminor (originally described as Helix triscalpta fraterminor Gredler, 1884: 137. T. triscalpta fraterminor Yen 1939: 126, pl. 13, fig. 8;Zilch 1974. T. fraterminor Yen 1943 as two distinct species, although the only known difference between them is that the latter species is "smaller in diameter and higher in altitude, obtusely angulated at periph-ery" (Pilsbry 1890). However, considering the frequency of convergence events in the evolution of shell morphology in the helicoids, it is reasonable to treat these two taxa that show detectable differences in shell morphology as two species. Traumatophora fraterminor is distributed between Hwang-tchou (today's Huangshi, Hubei Province) and Kiou-Kiang (today's Jiujiang, Jiangxi Province) (Pilsbry, 1890) (Fig. 1). Report of a Pleistocene fossil from Zhenjiang, Jiangsu as T. fraterminor (sensu Yen 1943) is somewhat doubtful because the relevant specimen was a juvenile shell.

Discussion
The anatomy of the terminal genitalia, especially the dart apparatus, varies greatly in the subfamily Bradybaeninae (Table 1) and is of considerable systematic significance. Most functions of these characteristic structures remain unclear, however,the function of some of these structures can be speculated to relate to the products of the dart apparatus, i.e., the love dart secreted in the dart chamber and the mucus secreted by the mucous glands, the function of which might be closely related to the reproductive success of the dart user as in the helicid snail Cornu aspersum (Lodi & Koene, 2016). Traumatophora, however, show an examples of the dart apparatus consisting of a tiny dart (proportionally the smallest in the Bradybaeninae) and disproportionately large mucous glands (proportionally the largest in the Bradybaeninae). Therefore, the genus Traumatophora provides a counter-example of the correlated evolution between stylophore and mucous glands (Koene and Schulenburg 2005: fig. 4A).
Traumatophora triscalpta has a rounded proximal accessory sac with an opening directly leading to the dart sac chamber. A similar structure is also present in some Stilpnodiscus species (S. moellendorffi Wu, 2001: Wu 2001aS. entochilus Möllendorff, 1899: Wu 2001a and in the Pseudiberus spp. distributed in Shandong and Hebei (unpublished) ( Table 1). The function of such sac-like structure is unknown, although it is predicted to be related to the storage of mucus secreted by the mucous glands. What is also fascinating is that in Traumatophora the occurrence of both the sphincter muscles in the accessory sac (Fig. 6A) and the developed nerve fibres connecting the mucous gland ducts (Fig. 5C, arrowed) suggests that during dartshooting in mating, there might be an instant ejection of mucus by the animal.