Discartemon deprima Siriboon & Panha

Siriboon, Thanit, Sutcharit, Chirasak, Naggs, Fred, Rowson, Ben & Panha, Somsak, 2014, Revision of the carnivorous snail genus Discartemon Pfeiffer, 1856, with description of twelve new species (Pulmonata, Streptaxidae), ZooKeys 401, pp. 45-107 : 61-63

9. Discartemon deprima Siriboon & Panha sp. n. Figs 5E, F, 23, Table 1

Type material.

Holotype CUMZ 6247 (Fig. 5E). Measurement: shell height 2.5 mm, shell width 8.2 mm, and with 5 whorls. Paratypes: CUMZ 3573 (2 shells), NHMUK 2013675 (1 shell), and SMF (1 shell) from the type locality. Paratype: CUMZ 6259 from Ban Tam Thong, Prathiew, Chumphon.

Other material examined.

Khao Pu-Khao Ya National Park, Sri Banphot, Phatthalung: CUMZ 3670.

Type locality.

Khao Hup Ta Hae, Prathiew, Chumphon, Thailand, 10°48'44.9"N, 99°25'9.0"E.

Diagnosis.

This species closely resembles Discartemon sykesi , but is distinct in having a concave spire and strong peripheral keel on the last whorl. Compared with Discartemon khaosokensis , Discartemon deprima sp. n. has a smaller shell with weaker transverse ridges, and the last whorl intermediately expanded. Discartemon deprima sp. n. differs from Discartemon nummus by having a larger shell, a concave spire, and one straight parietal lamella. It differs from Discartemon circulus sp. n. and Discartemon expandus sp. n. in having a concave spire, the last whorl intermediately expanded with a strong peripheral keel, and in having only one parietal lamella and a sinulus. In addition, Discartemon expandus sp. n. has transverse ridges that diminish below the periphery, and has a thin and widely expanded peristome.

Description.

Shell. Shell flattened, white and semi-transparent; whorls 5, spire concave with a distinct suture. Shell surface glossy with weak transverse ridges that diminish below periphery and appear again near peristome; varices present. Embryonic shell large, about 2½ whorls, with a smooth surface; following whorls regularly coiled. Last whorl angular with strong peripheral keel, intermediately expanded. Umbilicus very wide and showing all preceding whorls. Aperture semi-ovate with sinulus; peristome discontinuous, thin, expanded and reflected. Apertural dentition with only one parietal lamella (Fig. 5E).

Etymology.

The specific epithet “deprima” is derived from the Latin “deprimo” meaning “depress”. It refers to the depressed spire of this new species.

Distribution.

This species is known from the east coast of Chumphon, on an isolated limestone hill reaching about 200 meters amsl, and from a more southerly locality in Patthalung, a limestone hill complex reaching about 200-400 meters amsl.

Remarks.

There is some variation in this species in the discontinuous peristome and the presence of a sinulus. The samples from Patthalung (CUMZ 3670, 2 shells) have a continuous peristome and lack a sinulus. Currently, no living examples have been found.