Dalipaludina pyramidella (Du, Yang & Chen, 2011) Zhang & Du & von Rintelen, 2023

Zhang, Le-Jia, Du, Li-Na & von Rintelen, Thomas, 2023, A new genus of river snails, Dalipaludina (Gastropoda, Viviparidae), endemic to the Yunnan Plateau of SW China, Zoosystematics and Evolution 99 (2), pp. 285-297 : 285

Dalipaludina pyramidella (Du, Yang & Chen, 2011) comb. nov.

Trochotaia pyramidella Du, Yang & Chen, 2011: 85-89 (Yousuo village of Er-Yuan County, Yunnan, China).

Material examined.

Holotype, KIZ-DLN20100035; 19 paratypes, KIZ-DLN20100036 to KIZ-DLN20100054; 3 specimens in ZMB, 7 specimens in NJW, collected by Jiao-Wei Ning from 1 metre depth in the ponds of Yousuo Village , Eryuan County.

Description.

Shell (Fig. 6A-D ) large, conical, thin, greenish brown to brown in colour; up to six whorls at adulthood, including one relatively smooth protoconch whorl, apex acute, spire low; each teleoconch whorls with one strong keel at suture, above suture smooth, with two rings of short periostracum setae, base of shell smooth, with many rather thin weak spiral threads; aperture ovate, almost half of shell in height, lip thin and simple, umbilicus narrow, sometimes bordered by a keel.

Operculum (Fig. 6E ) corneous, ovate, rather thin, yellow or orange, with red nuclear region, exterior surface of operculum rather smooth, inner opercular region relatively small, nuclear region smooth.

Radular (according to Du et al. 2011) central tooth with one broad central denticle and three to four small sharp cusps on either side; lateral tooth with one broad central denticle and four small sharp cusps on either; inner marginal tooth with one broad central denticle and two small sharp cusps on either side; outer marginal tooth with 9 small sharp cusps.

Remarks.

This species differs from the other species of Dalipaludina by having a relatively smooth shell with lower spire. Du et al. (2011) assigned this species to Trochotaia mainly based on the strongly keeled shell with lower spire. However, characters of the operculum, embryonic shells, the reduced number of cusps on the outer marginal teeth (9 in D. pyramidella vs 14-16 in Trochotaia trochoides ) and the distribution in Yunnan strongly support its assignment to Dalipaludina . Species of Trochotaia have a very different operculum according to Zhang and von Rintelen (2021). This species is also quite similar to Cipangopaludina miyagii Kuroda, 1941 endemic to Kaohsiung, S Taiwan, China. It can be distinguished from C. miyagii by having a thinner shell, a shell base with many rather thin weak spiral threads, and a narrowly open umbilicus with a keel around it. The recommended Chinese name of this species is “塔形理田螺”.

Habitat and distribution.

shallow ponds with muddy bottoms and aquatic plant Ottelia acuminata (Gagnep.) in Yousuo Village, Eryuan County, Yunnan, China.

Figures

Figure 6. Shell and operculum of Dalipaludina pyramidella. A-C. Specimen collected from Eryuan County, ZMB. Moll. 122714; D. Varieties collected from Eryuan County, ZMB Moll. 122714; E. Exterior (left) and interior (right) surface of operculum. Scale bar: 1 cm, B-D with the same scale bar of A.