Serina denticulata, Wu, Min & Xu, Qin, 2013

Wu, Min & Xu, Qin, 2013, Serina Gredler (Gastropoda, Stylommatophora: Enidae), the continuous-peristomed mountain snails endemic to the eastern slope of the Qinghai-Xizang Plateau, Zootaxa 3620 (1), pp. 43-66 : 60-63

11. Serina denticulata , new species

Figs. 1 , 5 M–N, 8, 9; Tables 1–4 , 6

Types. Holotype: HBUMM-00281–specimen 5; Daigusi Village, Luoda (33°54ʹN, 103°54ʹE), Diebu County, Gansu, 2004–IV–29, colln. MW; measurements: ewh 1 3/4, wh 8 1/2, h 10.9 mm, w 3.5 mm, aph 3.3 mm, apw 2.5 mm. Paratypes, 25 fma, HBUMM- 0 0 281 –specimens 1~4 & 6~26; the same collection data as holotype.

Type locality. Daigusi (Gansu).

Etymology. The species name derives from the columellar tooth which can be observed from aperture.

Distribution. Gansu (only known from the type locality, Daigusi).

Diagnosis. Shell with the most swollen part occurred at penultimate whorl. Suture simple. Last whorl straight in front or ascending immediately near aperture; rounded at periphery. Aperture completely attached to body whorl. Aperture not duplicate. Columellar margin with a weak oblique spiral baso-columellar tooth and a more developed tooth above it.

Shell. Fusiform; with apex slightly abruptly pointed; dextral; with the most swollen part occurred at penultimate whorl; height 10.2–11.5–13.9, diameter major 3.5–3.9–4.5, ratio of height /diameter major 2.66–2.94–3.35. Growth lines usually not very clear. Whorls 8 1/8–8 3/4-–9 1/4, convex. Embryonic shell 1 5/8–1 3/4+–2 whorls. Postnuclear whorls smooth. Suture simple. Last whorl straight in front, or ascending immediately near aperture; rounded at periphery; abaperturally with a rugate region with crowded and/or thickened growthline-like folds. Aperture in a plane and straight; ovate, or subcircular; slightly oblique; completely attached to body whorl; armed; height 3.0–3.5–3.8, width 2.5–2.8–3.0, ratio of shell height /apertural height 2.96-3.30-3.82. Aperture not duplicate. Palatal tooth absent. Palatal margin rounded; toothless. Peristome and parietal callus almost completely fusing except for a channel at upper insertion of peristome. Reflexed part of peristome straight and not curved backward. Parietal callus distinct. Parietal tooth absent. Palatal wall without deep depression or tooth of irregular shape. Columellar margin reflexed; with a weak oblique baso-columellar spiral tooth and a more developed tooth above it; not sinuous. Columella arched. Umbilicus widely open. Shell light brown with a broad dirty white spiral band nearly occupying whole whorls; aperture white. Measured specimens: holotype and 19 paratypes.

Genitalia. Vas deferens short; evenly thick; entering epiphallus laterally with distinct demarcation. Epiphallus long; narrowed towards distal end; forming a few loops. Epiphallic caecum absent. Flagellum short; conic; proximally normal; with tip blunt. Penis clavate and distally enlarged; terminally entering epiphallus; thin-walled. Longitudinal pilasters more than two; fused at epiphallic pore forming velum; forming 1 V-shaped structure. Vshaped pilaster with proximal free end approaching at penial retractor insertion; without papilla formed by fused distal pilasters. Penial process absent. Penial appendix moderately long; branched off from proximal portion of penis; with A-1 fused with A-2, and with distinct A-3, A-4 and A-5. A-1 very short; without verge toward penial chamber; with longitudinal pilasters. A-2 internally with longitudinal pilasters; near A-3 internally with a ring of papilla. A-3 opening into A-2 by a long needle-like papilla. A-5 short; convoluted. Penial retractor biramous; with arms arising from diaphragm separately; with penial branch attaching to medial penis; with appendical branch attaching to A-1+A-2. Atrium short; with weak atrial retractor. Free oviduct moderately long; longer than vagina. Vagina very short; not swollen; straight. Bursa copulatrix duct very long; proximally twisted. Bursa copulatrix small; well defined; shortly with stalk; without apical ligament. Diverticle longer than reservoir; expanded. Bursa copulatrix and diverticle distinguishable; forked more distally from their base. Measurement of genitalia: See Table 2 (paratype HBUMM- 00281–specimen 1).

Taxonomic remarks. This species can be easily distinguished from all the other Serina species by the presence of two columellar teeth, one larger, occupying almost 1/2 whorl and can usually be partially observed through aperture, another one much smaller but distinct, just beneath the larger tooth.

Figures

FIGURE 1. Distribution of Serina species. S. soluta inflata Yen, 1939 is also indicated although synonymized in this paper. S. soluta stenochila (Möllendorff, 1901) is not mapped due to imprecise locality information.

FIGURE 5. A, B. Serina ser Gredler, 1898. A. SMF- 42036, Wangjiaba. B. ZI RAS N 76. C-E. Serina subser Gredler, 1898. C. NHM- 1902.5.13.23 – 24, Gansu. D. SMF- 42045, Wudu. E. HBUMM- 05392 – specimen 22, Lixian. F-K. Serina soluta (Möllendorff, 1901). F. NHM-Trechmann Acc. No. 2176, Dangchang. G. SMF- 42047, Wasigou. H, I. Serina soluta inflata Yen, 1939. H. HBUMM- 04318 – specimen 2, Luding. I. SMF- 42095, holotype, Kangding. J, K. Buliminus soluta stenochila Möllendorff, 1901. J. SMF- 42048, lectotype, valley of Daduhe River. K. SMF- 42049, paralectotype. L. Serina vincentii (Gredler, 1898), SMF- 42032, between Tshun-dshia-wan and Wangjiaba. M, N. Serina denticulata n. sp. M. HBUMM- 00281 – specimen 5, holotype, Daigusi. N. HBUMM- 00281 – specimen 6, paratype, Daigusi.