The top of the zone is defined by the evolutionary transition from Pterocodon? anteclinata to Buryella clinata and is coincident with the lower limit of the Buryella clinata Zone.
Events included in the zone are:
- Bm Theocotylissa alpha
- Bm Lamptonium fabaeforme chaunothorax
- Bm Pterocodon ? anteclinata; Bm Lophocyrtis jacchia
- Bm Calocycloma castum; Lamptonium pennatum -> Lamptonium fabaeforme fabaeforme
- Bm Podocyrtis papalis
- Tm Bekoma campechensis
The base of the zone is defined by the morphotypic first appearance of Bekoma bidartensis and is coincident with the upper limit of the Bekoma campechensis Zone.
Reference slides R 48.1, R 48.2 and R 48.3 from Sample 43-384-7-6, 119-125 cm.