Anulatrypa nieczlawiensis tenuicostata Tcherkesova

Modzalevskaya, Tatiana L., 2003, Silurian and Devonian brachiopods from Severnaya Zemlya (Russian Arctic), Geodiversitas 25 (1), pp. 73-107 : 92-93

Anulatrypa nieczlawiensis tenuicostata Tcherkesova in Modzalevskaya & Cherkesova, 1994 ( Fig. 21 A-H)

Anulatrypa nieczlawiensis tenuicostata Tcherkesova in Modzalevskaya & Cherkesova, 1994: 56, pl. V, figs 3-5. MATERIAL EXAMINED. — Five specimens from loc. 18095, Komsomolets Island ( Männik et al. 2002: fig. 1); Rusanov Formation.

REMARKS

The external features, such as ventral beak overlapping the top of dorsal beak; the absence of ventral interarea, fold and sulcus, numerous slen- der ribs; concentric lamellae extending into short trails allow to assign the specimens to the genus Anulatrypa . The sizes of adult specimens varie within the ranges: L = 11.2-28.6 mm, W = 9.3- 22.0 mm, T = 4.4-16.5 mm. The number of ribs is more than 30 at a distance of 5 mm from the ventral apex. These features characterize the specimens collected from the uppermost Tolbat and lower Daksan beds of Central Tajmyr, and allow to assign these to the subspecies A. nieczlawiensis tenuicostata . The Severnaya Zemlya specimens differ from those from Tajmyr (Modzalevkaya & Cherkesova 1994: 56) by possessing weakly longitudinal outline, and straight hinge line ending in the round- ed ears. The specimens from Severnaya Zemlya have some similarities in size, in outline, and in ornamention with Anulatrypa hyperanulata Havlic˘ek, 1987 from Zlichovian of Central Bohemia (Havlic˘ek 1987: 75, pl. 1, fig. 5). Specimens from both regions possess a narrow tongue in the anterior margin, but those from Severnaya Zemlya lack a ventral sinus.

A. nieczlawiensis tenuicostata has been found from Central Tajmyr, from the Delorm Formation in the Canadian Arctic Cathedral Mountains, and in the Bystrin Formation on Novaya Zemlya ( Modzalevskaya & Cherkesova 1994).

Family LISSATRYPIDAE Twenhofel, 1914

Figures

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.