Lavachilina evae, Tinn & Meidla, 2002

Tinn, Oive & Meidla, Tõnu, 2002, An enigmatic early? palaeocope ostracode from the Arenig of NW Russia, Acta Palaeontologica Polonica 47 (4), pp. 685-690 : 686

Lavachilina evae sp. nov.

Fig. 3 .

Holotype: Right valve TUG1/1099; Lava River, Russia; Volkhov Stage (about 2 m from the upper boundary of the Volkhov Stage; see Fig. 1 ), Arenig, Middle Ordovician.

Derivation of the name: The species is named in honour of Eva Egerquist, a Swedish palaeontologist, who donated the specimens for this study. Diagnosis.—Length of the largest specimen reaches 3.0 mm.

Valves sub−triangular, faintly convex and non−sulcate; strongest valve convexity in the mid−ventral region. Whole valve surface, except for the muscle field, ornamented with fairly large punctae. Adductorial muscle scar large, smooth and drop−shaped. Discontinuous velum developed antero− and posterodorsally as a spinose ridge.

Figures

Fig. 3. Lavachilina evae sp. nov. A. TUG 1/1099, Lava River, Russia, Volkhov Stage. Right valve. In lateral (A1), × 17; oblique ventral (A2), × 17; ventral (A3), × 17; posterior (A4) views, × 23; detail of posterior view (A5), × 85; and detail of posterior view (A6), × 54. B. TUG 5/1099, Lava River, Russia, Volkhov Stage. Right valve. In lateral (B1), × 17; oblique ventral (B2), × 17; and ventral (B3) views, × 17. C. TUG 3/1099, Lava River, Russia, Volkhov Stage. Left late preadult valve. In oblique lateral (C1), × 19; lateral (C2), × 19; and ventral (C3) views, × 19. D. TUG 4/1099, Putilovo, Russia, Volkhov Stage. Deformed carapace. In anterior (D1), × 17; and antero−ventral, detail (D2) views, × 89. E. TUG 2/1099, Putilovo, Russia, Volkhov Stage. Left valve. Interior view (E1), × 19; cross−section of the valve (E2), × 61; adductorial muscle scar area (E3), × 42.

Fig. 1. Location of the studied sections in the St. Pe−