Discartemon planus (Fulton, 1899)

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 : 54-55

2. Discartemon planus (Fulton, 1899) Figs 4D, 23

Streptaxis planus Fulton, 1899: 214, pl. 11, fig. 2. Type locality: South Celebes. Gude 1903: 227. Laidlaw 1933: 233. Sarasin and Sarasin 1899: 228.

Odontartemon (Discartemon) planus - Kobelt 1906: 100, 101, pl. 54, figs 15-17. Kobelt 1910: 150. Laidlaw 1929: 260.

Discartemon planus - Benthem Jutting 1954: 79. Bruggen 1972: 394. Richardson 1988: 183. Maassen 1997: 55. Marwoto 2008: 191-194, fig. 1.

Material examined.

Celebes [=Sulawesi], Indonesia: NMW 1955.158.25252 (1 shell; Fig. 4D).

Remarks.

The shell of this species is clearly distinct from all other recognized species. Shell flattened, with a concave spire and distinct suture. Shell surface smooth, varices present; whorls regularly coiled. Last whorl rounded with keel below periphery, rapidly expanded; umbilicus very wide, concave and showing all preceding whorls. Aperture triangular with long and narrow sinulus, peristome thickened and little reflected. Apertural dentition with one parietal, one palatal and one columellar lamella (Fig. 4D) ( Fulton 1899, Kobelt 1906, Marwoto 2008).

The distribution of Discartemon planus seems to be outside the ranges of all other Discartemon species, and is probably restricted to the limestone karst in the south of Sulawesi ( Fulton 1899, Sarasin and Sarasin 1899, Laidlaw 1929, Bruggen 1972, Marwoto 2008). It does not closely resemble any other streptaxid genus more closely than Discartemon . However, the very wide umbilicus showing all preceding whorls and surrounded with a keel, with a long and narrow adapical sinulus, may indicate that Discartemon planus comprises a distinct lineage within Discartemon . Both Bruggen (1972) and Marwoto (2008) discussed the possibility that it required a separate genus or subgenus, but anatomical or molecular evidence are desirable to support this assertion.