The top of the zone is defined by the morphotypic last appearance of Stichocorys peregrina and is coincident with the lower limit of the Lamprocyrtis heteroporos Zone.
Events included in the zone are:
- Bm Stylacontarium acquilonium
- Tm Stichocorys delmontensis
- Bm Lamprocyrtis heteroporos
- Tm Theocorys redondoensis
The base of the zone is defined by the morphotypic first appearance of Sphaeropyle langii and is coincident with the upper limit of the Stichocorys peregrina Zone.
The range of this zone approximates that of the Spongaster pentas Zone in the equatorial Pacific.
Subsequent unpublished studies (Kling, pers. comm., 1992) and our own observations suggest that Sphaeropyle langii and Sphaeropyle robusta are not stratigraphically useful species and that the radiolarian zonation in this part of the time scale will need to be revised.Reference slides R 54.1, R 54.2 and R 54.3 from Sample 32-310-7-2, 83-90 cm.