| original |
Early Ordovician |
Late Ordovician |
Finland |
Tynni,R. On Paleozoic microfossils in clastic dykes on the …land Islands and in the core samples of Lumparn. (In: Paleozoic sediments in the Rapakivi area of the …land Islands. L. Bergman, R. Tynni and B. Winterhalter, editors.) |
1982 |
| details |
Ordovician |
|
Nd |
Fensome,R.A. et al. Acritarchs and Fossil Prasinophytes: An index to genera, species and infraspecific taxa. |
1990 |
| details |
Middle Ordovician |
|
Finland |
Playford,G. et al. Ordovician acritarch genera Peteinosphaeridium, Liliosphaeridium and Cycloposphaeridium: Morphology, taxonomy, biostratigraphy and palaeogeographic significance |
1995 |