| original |
Early Ordovician |
Middle Ordovician |
USSR(Russian Platform) |
Umnova,N.I. Structural types of the Prosome and Operculum in the chitinozoa and their association with genera and species. |
1976 |
| details |
Early Arenigian |
|
Canada(Quebec) |
Achab,A. Chitinozoa from the Lower Arenig of the Levis Formation, (Quebec, Canada). |
1980 |
| details |
Early Ordovician |
Middle Ordovician |
USSR(Russian Platform) |
Umnova,N.I. Ordovician and Silurian chitinozoa from the northern part of the Russian Platform. |
1981 |
| details |
Middle Arenigian |
|
Canada(Quebec) |
Achab,A. Chitinozoa assemblages of the Early Ordovician of eastern Canada. |
1986 |