(Riedel and Sanfilippo, 1970, emend. 1971, 1978a)
The top of the zone is defined by the evolutionary transition from Tristylospyris triceros to Dorcadospyris ateuchus and is coincident with the lower limit of the Dorcadospyris ateuchus Zone.
Events included in the zone are:
- Bm Didymocyrtis prismatica; Tm Dorcadospyris pseudopapilio
- Centrobotrys gravida -> Centrobotrys petrushevskayae; Bm Dorcadospyris pseudopapilio
- Bm Lithocyclia crux; Artophormis barbadensis ->Artophormis gracilis
- Tm Dictyoprora pirum; Bm Phormostichoartus fistula
- The lower limit of the zone is approximately synchronous with Tm Cryptocarpium ornatum; Tm Dictyoprora mongolfieri; Tm Lychnocanoma amphitrite
The base of the zone is defined by the evolutionary transition from Lithocyclia aristotelis group to Lithocyclia angusta and is coincident with the upper limit of the Cryptocarpium ornatum Zone.
Reference slides R 33.1, R 33.2 and R 33.3 from Sample 85-573B-34-CC; R 34.1, R 34.2 and R 34.3 from Sample 85-573B-35-CC; R 35.1, R 35.2 and R 35.3 from Sample 85-573B-37-CC.