The base is also close to the extinction level of the calcareous nanoplankton species Triquetrorhabdulus rugosus (the base of biozone CN10b) and the first appearance of nannoplankton Ceratolithus acutus.
The base of the Tortonian stage is at the last common appearance of calcareous nannoplankton Discoaster kugleri and planktonic foram Globigerinoides subquadratus.