(Riedel and Sanfilippo, 1970)

The top of the zone is defined by the evolutionary transition from Diartus petterssoni to Diartus hughesi and is coincident with the lower limit of the Didymocyrtis antepenultima Zone.

Events included in the zone are:

- Tm Eucyrtidium inflatum

The base of the zone is defined by the morphotypic first appearance of Diartus petterssoni and is coincident with the upper limit of the Dorcadospyris alata Zone.

Although equivalent to the low-latitude zone of the same name, the aspect of the fauna in middle latitudes is often different and important marker species are frequently missing.

Reference slides R 58.1, R 58.2 and R 58.3 from Sample 18-173-22-4, 18-24 cm.