Abstract

A monographic study of Tentaculitida, Nowakiida and Styliolinida from Palaeozoic deposits of the USSR has made possible the discrimination of more than one hundred new species, and the erection of a viable classification.

Many genera, some families, and three Orders (Tentaculitida, Nowakiida, Styliolinida) had been distinguished and united into a new Class, Coniconchia. Subsequently, hyolithes have been included in the Class.

Coniconchia occur in Devonian, Silurian and, rarely in Ordovician deposits of all continents, in rocks of various facies, i.e. shales, siltstones, marls, and limestones of different colours, deposited in basins of “normal-marine” (“open-neritic”) or of euxinic habitat. In some cases, they constitute rock forming fossil. Because of wide geographic distribution and limited stratigraphic range of certain species of Coniconchia, the order is of value in the separation and correlation of detailed stratigraphic subdivisions.

Coniconchia from Devonian deposits of the Russian platform have received detailed consideration, the writer having distinguished, in 1965, some twenty zones.

Study of the material from the Soviet Arctic, Urals, Siberia, central Asia, Caucasus, etc., show that Coniconchia are widely developed within these regions, and have some important guide species, the significance of which extends into other regions and sequences.

Undoubtedly, the stratigraphic importance of Coniconchia will be increased as their study progresses.