The top of the zone is defined by the morphotypic first appearance of Bekoma bidartensis and is coincident with the lower limit of the Bekoma bidartensis Zone.
Events included in the zone are:
- Bm Phormocyrtis cubensis
- Tm Buryella pentadica
- Bm Pterocodon ampla
The base of the zone is defined by the morphotypic first appearance of Bekoma campechensis and is underlain by unzoned Paleocene. Events in this unzoned portion of the Paleocene include Bm Lamptonium pennatum and Bm Buryella pentadica.
Reference slides R 49.1, R 49.2 and R 49.3 from Sample 43-384-7-6, 119-125 cm.