(Riedel and Sanfilippo, 1970, emend. 1978a)
The top of the zone is defined by the morphotypic first appearance of Cyrtocapsella tetrapera and is coincident with the lower limit of the Cyrtocapsella tetrapera Zone.
An event included in the zone is:
- Tm Dorcadospyris papilio
- The lower limit of the zone is approximately synchronous with Bm Carpocanopsis cingulata
The base of the zone is defined by the morphotypic first appearance of Lychnocanoma elongata and is coincident with the upper limit of the Dorcadospyris ateuchus Zone. This upper zonal boundary is approximately equivalent to the Oligocene-Miocene boundary.
Reference slides R 28.1, R 28.2 and R 28.3 from Sample 85-573B-19-CC; R 29.1, R 29.2 and R 29.3 from Sample 85-573B-20-CC.