Dihelictera cf. lepidota (Nikiforova & T. Modzalevskaya, 1968)

Modzalevskaya, Tatiana L., 2003, Silurian and Devonian brachiopods from Severnaya Zemlya (Russian Arctic), Geodiversitas 25 (1), pp. 73-107 : 89

Dihelictera cf. lepidota (Nikiforova & T. Modzalevskaya, 1968) ( Figs 19 ; 21I )

cf. Protatrypa lepidota Nikiforova & T. Modzalevskaya, 1968: 61 , pl. II, figs 8, 9.

MATERIAL EXAMINED. — Eight specimens from loc. 11, beds 14 and 14-A, and loc. 2, beds 74 and 79 (only fragments), Matusevich River, October Revolution Island ( Männik et al. 2002: figs 2, 5); Samojlovich Formation. Two poorly preserved specimens from samples 2zh/76, 2i/76, Pioneer Island ( Männik et al. 2002: fig. 1); Srednij Formation.

REMARKS

Specimens are small, with a ventral keel-like ridge and dichotomous ribs. Ribs are crossed by concentric growth lamellae which are most pronounced anteriorly. The internal structure is typical of the genus Dihelictera to which Protatrypa lepidota Nikiforova & T. Modzalevskaya, 1968 ( Nikiforova & Modzalevskaya 1968: 61, pl. II, figs 8, 9) is assigned by P. Copper (1995: 855) ( Fig. 19 ). This species is widespread in the Omnutakh and Khukta formations of East Siberia and Gora Gjiaden’ Formation of Salair (Ivanovsky & Kul’kov 1974: 59, pl. XX, figs 6, 7).

Figures

FIG. 19. — Selected transverse serial sections, illustrating the development of internal structures in Dihelictera cf. lepidota (Nikiforova & T. Modzalevskaya, 1968); A, ventral valve (N 48/12991), length 10.2 mm, loc. 2, bed 79, Samojlovich Formation; B, dorsal valve (N 49/12991), length 10.0 mm; loc. 11, bed 14, Samojlovich Formation. Numerical designations are the same as on Fig. 11. Scale bar: 2.3 mm.

FIG. 21. — A-H, Anulatrypa nieczlawiensis tenuicostata Tcherkesova in Modzalevskaya & Cherkesova, 1994; A, E, ventral view; B, F, dorsal view; C, G, lateral view; D, H, anterior view of a young and adult complete shells (N 55/12991, 56/12991), loc. 18095, Rusanov Formation; I, Dihelictera cf. lepidota (Nikiforova & T. Modzalevskaya, 1968), ventral view of a pedicle valve (N 47/12991), loc. 2, bed 79, Samojlovich Formation. Scale bars: A-D, I, 5 mm; E-H, 6 mm.