Trimerella sp.

Modzalevskaya, Tatiana L., 2003, Silurian and Devonian brachiopods from Severnaya Zemlya (Russian Arctic), Geodiversitas 25 (1), pp. 73-107 : 75

Trimerella sp. ( Fig. 1 )

MATERIAL EXAMINED. — Numerous ventral shells (concentrated in shell bank) from the single locality, loc. 13e, Srednij Island (Sedov Archipelago, Männik et al. 2002: fig. 1); Srednij Formation.

REMARKS

Within the group of Telychian brachiopods assigned here to Trimerella are forms with ventral shells of medium size, longitudinally oval outline, and the convex umbo. The ventral pseudointerarea with homeochilidium is not visible. A low ventral muscle platform extends behind the middle of the valve. Short lateral septum occurs at less than 18° from the longer septum, which extends almost to the anterior margin. Trimerella is a common genus from the Ashgill through the Silurian of the North America, Europe, East Siberia, Australia, South China, Kazakhstan and Tuva. In their size and convexity, the shells resemble those of Trimerella attenuata Gorjansky, 1972 from the Donenzhal Formation of Kazakhstan (Tarbagataj ridge) ( Gorjansky 1972: 171, pl. 45, figs 6, 7). The specimens from Severnaya Zemlya differ from those known from other regions in possessing a shell which is wider anteriorly and has a longer median septum. Larger but very similar shells are described from the Omnutakh and Mogokta formations in East Siberia (Lopushinskaya 1991: 51, pl. I, figs 1-5).

Figures

FIG. 1. — Trimerella sp., pedicle valve (N 1/12991), loc. 13e, Srednij Formation; A, posterior view; B, ventral view. Scale bar: 6 mm.