| original |
Ashgillian |
|
Oklahoma |
Loeblich,A.R.,Jr. et al. Some Middle and Late Ordovician microphytoplankton from Central North America. |
1978 |
| details |
Early Paleozoic |
|
Nd |
Cramer,F.H. et al. Lower Paleozoic acritarchs. |
1979 |
| details |
Ashgillian |
|
Nd |
Fensome,R.A. et al. Acritarchs and Fossil Prasinophytes: An index to genera, species and infraspecific taxa. |
1990 |
| details |
Early Caradocian |
|
Sweden |
Wallin,A. et al. Biostratigraphical investigation of Middle Ordovician acritarch the post-impact sequence in the Tvaren-2 core, Sweden. |
1996 |