Plekocheilus (Eurytus) fusitorsus ( Oberwimmer, 1931 )

Breure, Abraham S. H., 2009, New Orthalicidae (Mollusca, Gastropoda) from Venezuelan Guayana: unravelling secrets from the Lost World, Zootaxa 2065, pp. 25-50 : 35

Plekocheilus (Eurytus) fusitorsus ( Oberwimmer, 1931)

( Figs 4 H─L, 9I)

Eurytus fusitorsus Oberwimmer, 1931: 190 , figs 1, 4. Type locality: Venezuela, Territorium Amazonas, Río Padamo; holotype SMF 5142.

Material. Venezuela, Estado Bolívar, Cerro Guaiquinima, along Río Paragua, 1500 m, J.A. Steyermark leg., 1978, in wooded portion of moist dwarf forest ( FMNH 198500/1); Estado Amazonas, Río Padamo ( SMF 5142/ holotype).

Shell dimensions are given Table 1 .

Remarks. This species is characterized by dark, undulating stripes on the last whorl bordered by a yellowish ‘shadow’ and a fine granulation of dotted granules (Fig. 9I). A subadult specimen from Cerro Guaiquinima (FMNH 198500) is tentatively referred to this species. It is characterized by the same colour pattern as observed in the holotype, but has oblong granules on the upper part of the last whorl, giving an impression of spiral incisions in between.

The type locality is a river basin that covers 10.280 square km and drains the northwestern slopes of the Sierra Parima on the east-central border of Estado Amazonas in Venezuela and Estado Roraima in Brazil ( Huber 1995a). Río Padamo is slightly east of Cerro Duida [type locality of Plekocheilus (Eurytus) tatei Haas, 1955 ] and Cerro Marahuaka [type locality of P. (E.) gibber ( Oberwimmer, 1931) ]. The headwaters of Río Padamo are on Cerro Kikirisha, slightly over 1000 m, but along its course elevations of 500 m or less prevail. Since the exact type locality is unknown, it cannot be excluded a priori that P. (E.) fusitorsus also occurs in the lowland. This species might also be expected at intermediate localities in between the two occurrences, e.g. in the Jaua-Sarisariñama massif.

Figures

FIGURE 4. Shells in Plekocheilus. A ─ D. P. (P.) fulminans linterae (Sowerby, 1890). A ─ C. Lectotype, BMNH 1889.4.25.1; D. Paralectotype BMNH 1889.4. 25.2. Photos P. Crabb. E ─ G. P. (P.) fulminans alticola Haas, 1955, holotype FMNH 52442. H ─ L. P. (Eurytus) fusitorsus (Oberwimmer, 1931). H ─ J. Holotype SMF 5142; K ─ L. FMNH 198500. M ─ O. P. (E.) gibber (Oberwimmer, 1931), holotype SMF 5143. Scale bar— 1 cm.