Strepsitaurus susieae, Taylor & Johnson & Stankowski, 2015

Taylor, James P. A., Johnson, Michael S. & Stankowski, Sean, 2015, Molecular phylogenetics and complementary geographical distributions of species of the Western Australian land snail genera Plectorhagada Iredale, 1933 and Strepsitaurus Solem, 1997 (Gastropoda: Camaenidae), Zoological Journal of the Linnean Society 174 (2), pp. 305-321 : 320

STREPSITAURUS SUSIEAE SP. NOV.

FIGURES 1 , 3 , 7, 12

Type locality

Western Australia, Cape Range, in small gorge south of Tulki Gorge (22°05′46.7″S, 113°54′19.6″E) .

Material examined

Holotype: WAM S67368 . Paratypes: WAM S59657 .

Etymology

Refers to Susie Johnson, who has assisted extensively with collections of Western Australian camaenids, including the discovery of this species.

Description

Holotype: shell 7.1 mm wide, 4.1 mm high, H / D ratio 0.57, with 3.6 whorls. Based on five measured adults, shell small, diameter 7.1–7.5 mm (mean 7.33 mm, SD 0.35 mm), with 3.63–3.75 (mean 3.5, SD 0.12) whorls. Apex and spire evenly elevated, shell height 4.1– 4.3 mm (mean 4.22, SD 0.09 mm), H / D ratio 0.544 – 0.597 (mean 0.575, SD 0.019). Body whorl rounded, without trace of angulation. Protoconch densely pustulose. Early spire with prominent ridges and pustules. Lower spire and body whorl with very prominent, deeply pustulose diagonal ridges, both above and below periphery. Umbilicus wide, regularly decoiling, slightly narrowed by columellar lip, width 1.5– 1.9 mm (mean 1.72 mm, SD 0.11 mm). Body whorl descending sharply behind aperture. Palatal and basal lips sharply reflected and broadly expanded, and columellar lip wide, parietal lip free of wall and strongly elevated. Basal lip with or without weak knob on top of lip. Shell colour white on top of ridges, reddish brown in interstices.

Comparative remarks

Strepsitaurus susieae sp. nov. is similar to S. milyeringus and S. manduensis sp. nov., with these three species differing from S. ningaloo , S. rugus , and S. williami by their small size, low whorl count, lips distinctly detached from the body whorl, and lack of setae on the shell. They also lack the prominent knob on the basal lip, which characterizes S. williami ( Solem, 1997) . Strepsitarus susieae sp. nov. is distinguished from S. milyeringus and S. manduensis sp. nov. by its relatively higher spire [mean H/D 0.575 (0.544 –0.597), compared with 0.484 (0.443 –0.548) and 0.449 (0.407 – 0.479)], and its very prominent ridges both above and below the periphery of the body whorl.

Distribution

This species has been found only in an unnamed small gorge (∼ 1.2 km long), south of Tulki Gorge, on the west side of Cape Range. All specimens were found on or at the base of the vertical north wall of the gorge during wet weather.

Figures

Figure 1. Sample sites for Plectorhagada and Strepsitaurus. Large map (between North West Cape and Cape Range in the north and Shark Bay in the south) shows sites for Plectorhagada and southernmost sample sites of Strepsitaurus ningaloo (SNA, SNB). The shaded area is the known distribution of Strepsitaurus. The expanded map shows central Cape Range, with the sample sites of Strepsiaurus. Dotted lines indicate recorded distributions of species, based on Solem (1997). Open circles indicate sites for species restricted to gorges on the western side of the Cape Range, the shells of which are shown in the lower right corner. Site codes as described in Table 1.

Figure 3. Maximum-likelihood (ML) tree for Plectorhagada and Strepsitaurus based on concatenated sequences of COI and 16S. Inset shows relationships with the out-groups. Numbers indicate bootstrap support for the ML tree, all of which were less than or equal to the posterior probabilities from the Bayesian analysis.

Figure 12. Shells of Strepsitaurus milyeringus (A–C), and holotypes of Strepsitaurus susieae sp. nov. (D–F) and Strepsitaurus manduensis sp. nov. (G–I).