What is "eupachydiscus"

Eupachydisus is a large, coarse-ribbed Pachydiscid ammonite genus from the Upper Cretaceous, found in Coniacian to Campanian age strata in Europe, Madagascar, Japan, and British Columbia.

The whorl section in Eupachydiscus is inflated and depressed, almost round in the later growth stages. Ribs are narrow but prominent in the early whorls, becoming thick and strong in the later.

Eupachydiscus is distinct from the mostly later, Campanian - Maastrichtian, compressed and high-whorled Pachydiscus, but somewhat similar to the coeval, inflated and coarse ribbed, Coniacian- Santonian, Pachydiscoides