Tibatrochus cf. incertus ( Schepman, 1908 )

Herbert, David G., 2015, An annotated catalogue and bibliography of the taxonomy, synonymy and distribution of the Recent Vetigastropoda of South Africa (Mollusca), Zootaxa 4049 (1), pp. 1-98 : 31

Tibatrochus cf. incertus ( Schepman, 1908) —new record

( Figures 4 G–J, 10A, B)

Priotrochus (?) incertus Schepman, 1908: 45 , pl. 2, fig. 4; Van der Bijl et al., 2010: 60, 124. Type loc.: Siboga St’n 59, western entrance Samau-Strait, 390 m; holotype originally in ZMA (3.08.030), now in RMNH.

Tibatrochus incertus — Poppe et al., 2006: 46, pl. 15, figs 1, 2.

Distribution. Central Indo-West Pacific to central Mozambique, KwaZulu-Natal and southern Transkei (off Shixini Point); 95–500 m (living 95–250 m).

Notes. This material closely resembles Tibatrochus incertus from S.E. Asia, but in most of the western Indian Ocean material the suture is less strongly indented and the subsutural region is almost smooth, as opposed to distinctly coronate. There are, however, some local specimens in which the axial ribs extend to the adapical suture, rendering the shoulder region strongly undulant or nodular ( Fig 4 I). Occasional individuals from Mozambique have weaker sculpture ( Fig. 4 J) and may also have and additional spiral cord above and/or below the periphery. This variation in sculpture needs to be evaluated in more detail before a decision on the status of the local material can be made. As with Calliotropis eucheloides above, it may be that a single sculpturally variable species is involved. The radula of this genus has not previously been illustrated, so I take the opportunity to do so ( Fig. 10 A, B). As expected in calliotropid taxa, the rachidian is hooded, but unlike species of Calliotropis , there are five pairs of lateral teeth (rather than three) and there is no latero-marginal plate, although the base of the shaft of the fifth lateral is somewhat expanded.

Figures

FIGURE 10. Radulae. A, B, Tibatrochus cf. incertus (Schepman, 1908), scale bars 100 Μm and 25 Μm respectively (NMSA E 331). C, D, Skenea fuscomaculata (G. B. Sowerby (III), 1892), scale bars 50 Μm and 20 Μm respectively (NMSA V 357). E, F, Zetela turbynei (Barnard, 1963), scale bars 250 Μm and 100 Μm respectively (NMSA V 5510).

FIGURE 4. A – C, Calliotropis bucina Vilvens, 2006, off Tongaat Bluff, KwaZulu-Natal, 235 m, diameter 5.3 mm (NMSA S 66). D – F, Calliotropis eucheloides B. A. Marshall, 1979, off Mbashe River, E. Cape, 295 – 300 m, diameter 10.1 mm (NMSA C 9006). G – J, Tibatrochus cf. incertus (Schepman, 1908); G, H, off Nthlonyane River, E. Cape, 95 m, length 6.4 mm (NMSA E 331); I, off Glenton Reef, KwaZulu-Natal, 200 – 210 m, length 6.9 mm (NMSA S 456); J, off Beira, Mozambique, 200 – 220 m, length 6.3 mm (NMSA L 2765). K, L, Seguenzia orientalis Thiele, 1925, off Mgazi River, E. Cape, 350 m, length 2.3 mm (NMSA C 9563). M, Visayaseguenzia compsa (Melvill, 1904), off Gipsy Hill, KwaZulu-Natal, 65 – 70 m, diameter 2.3 mm (NMSA E 7465). N – P, Skenea fuscomaculata (G. B. Sowerby (III), 1892), off Struisbaai, W. Cape, 32 m, diameter 3.0 mm (NMSA V 357). [Images not to scale.]