Gulella (Molarella) sexdentata (von Martens, 1869)

Muratov, Igor V., 2010, Terrestrial molluscs of Cabo Delgado and adjacent inland areas of north-eastern Mozambique, African Invertebrates 51 (2), pp. 255-255 : 273

Gulella (Molarella) sexdentata (von Martens, 1869)

Fig. 34

Ennea laevigata var. sexdentata von Martens, 1869 b: 154 ( Zanzibar; 9.5×4.0 mm).

Ennea sexdentata: von Martens, 1897: 22 .

Ennea sexdentata var. liederi von Martens, 1897: 22 (Kitohaui on the plateau between Ukuledi and Umbekuru, District Mgao; 12× 6 mm).

A common eastern African species with a general distribution from northern Tanzania to the Save River in central Mozambique. Found at three stations inland and one on Cabo Delgado. Differs from other Streptaxidae in the area by the smooth ovalcylindrical shell with a single large curved parietal lamella, three to four palatal teeth, one basal tooth and a small cusp situated on top of the large horizontal columellar lamella. It is represented in the studied area by the var. liederi von Martens, 1897 . Typical shells of sexdentata var. liederi ( Fig. 34 ) were found at three stations inland. The illustrated shell has a barely noticeable fourth palatal lamella, which is completely absent in all other shells from inland stations. All four shells from the easternmost station on Cabo Delgado have a well-developed fourth short palatal lamella just below the regular three, and I consider these shells to be another variety not deserving a separate name.

Var. liederi was described from south-eastern Tanzania only about 150 km northwest of the study area. It differs from typical Gulella sexdentata by the presence of a small cusp on top of the much stronger columellar lamella. Germain (1935: 4) agreed with von Martens (1897: 22) that the 10× 5 mm Ennea hanningtoni described by Smith (1890: 161, pl. 6, fig. 4) from northern Tanzania is a synonym of sexdentata . Connolly (1925: 117; 1939: 62) also treated hanningtoni as a synonym of sexdentata . He gave a 7.7–10.5 × 3.7–5.0 mm size range for this species and indicated the rare presence of “a minute additional denticle on the columellar lip” as well as occasionally lacking an upper palatal tooth (Connolly 1939: 62).

G. sexdentata (von Martens, 1869) is part of the complex of allied species inhabiting East and Central Africa. It is replaced by G. ugandensis (Smith, 1901) (syn. Ennea optata Preston, 1911 ) in Kenya and G. aliciae (Melvill & Ponsonby, 1907) in northern KwaZulu-Natal.

Figures

Figs 30–38.Streptaxidae:(30) Edentulina affinis,33.4×17.6 mm,stn 5; (31) Taylorialeroyi, 14.4×21.0 mm, stn 5; (32) Gonaxis cf. percivali, 9.4×6.9 mm, stn 1; (33) G. denticulatus, 7.0×4.6 mm, stn 11; (34) Gulella sexdentata var. liederi, 9.4×4.8 mm, stn 1; (35) G. subhyalina, 6.5×2.3 mm, stn 1; (36) G. perissodonta, 3.2×1.5 mm, stn 7; (37) Gulella delgada sp. n., 4.0×1.8 mm, 1st syntype, stn 7; (38) Streptostele herma, 3.8×1.2 mm, stn 7. Scale bar 10 mm in Figs 30–31; 3 mm in Figs 32–34; 1 mm in Figs 35–38.