Eohowellella sp.

Modzalevskaya, Tatiana L., 2003, Silurian and Devonian brachiopods from Severnaya Zemlya (Russian Arctic), Geodiversitas 25 (1), pp. 73-107 : 94

Eohowellella sp. ( Fig. 24A )

MATERIAL EXAMINED. — Four specimens from loc. 11, bed 14, and coquina from loc. 2, beds 74, 79, Matusevich River, October Revolution Island ( Männik et al. 2002: figs 2, 5); Samojlovich Formation.

REMARKS

Small, subrhomboidal shells of the genus Eohowellella are widely variable. They have rounded cardinal extremities, four plicae arising near the beak and rapidly widening anteriorly. The width of the plicae is four times more than the interspaces. The shells studied possess a combination of features characteristic of two different species of Eohowellella . The size and weakly developed plicae on the both valves are characteristic of E. yadrenkinae Lopushinskaya, 1976 , whilst the flat dorsal valve with distinctly developed trilobite external structure, and numerous concentric growth lines, are typical to E. minimus Lopushinskaya, 1976 . Both of these species occur in the Talikit, Omnutakh, Khukta and Makus formations in the East Siberia ( Lopushinskaya 1976: 80). Small size, plicae wider than interspaces, and almost flat dorsal valve are also characteristic of Howellella elegans (Muir-Wood, 1925) , the holotype of which comes from the Mulde Beds of Gotland ( Bassett & Cocks 1974: 38, pl. 10, fig. 5). The Severnaya Zemlya specimens have an erect ventral umbo, subrhombical outline and more numerous plicae than H. elegans .

Family RETICULARIIDAE Waagen, 1883

Figures

FIG. 24. — A, Eohowellella sp., ventral view of a pedicle valve (N 64/12991), loc. 2, bed 79, Samojlovich Formation; B-F, Reticulariopsis talenti Lenz & Johnson, 1985; B, ventral view; C, dorsal view; D, lateral view; E, posterior view of a complete shell (N 65/12991); F, posterior view of a complete shell (N 66/12991), showing delthyrium, loc. 21581, Severnaya Zemlya or Pod’’emnaya formations. Scale bar: A, 5 mm; B-E, 2 mm; F, 2.5 mm.