Alispira gracilis (Nikiforova & Andreeva, 1961)

Modzalevskaya, Tatiana L., 2003, Silurian and Devonian brachiopods from Severnaya Zemlya (Russian Arctic), Geodiversitas 25 (1), pp. 73-107 : 90

Alispira gracilis (Nikiforova in Nikiforova & Andreeva, 1961)

Zygospira (Alispira) gracilis Nikiforova in Nikiforova & Andreeva, 1961: 244, pl. LIII, figs 1-8.

Alispira gracilis – Rubel 1970: 25, pl. XIII, figs 16- 22. — Lopushinskaya 1976: 63, pl. XI, figs 1, 2.

MATERIAL EXAMINED. — Two specimens from loc. 12, bed 112, Matusevich River, October Revolution Island ( Männik et al. 2002: figs 2, 5); Vodopad Formation.

REMARKS

Specimens have a ventral valve with a keel on the umbo, and an acute, weakly incurved beak. The sinus is well defined: arising at the umbo, it is bordered by larger ribs and commonly bears one or two weaker ones. The lateral ribs increase in width anteriorly. The number of ribs multiplies by bifurcation and intercalation. Based on these features the specimens are assigned to Alispira gracilis which is typical of the Chamba and Talikit formations of East Siberia. Homeospira? sp. ( Poulsen 1934: 19, pl. 2, figs 21, 22) from the Cape Schuchert Formation of Greenland resembles A. gracilis . O. I. Nikiforova thought that, in reality, the last one should also be assigned to A. gracilis ( Nikiforova & Andreeva 1961) .