Aptian–Albian (Lower Cretaceous) ammonite biostratigraphy of the Miyako Group, Japan based on supplementary and revised ammonite taxa

The Early Cretaceous ammonite standard zonation based on the Tethyan Realm is found in western Europe. Because marine faunas also thrived in the Tethyan, Boreal (Arctic), and Pacific regions during the Early Cretaceous, it is important to establish additional biochronological scales based on the faunas of each of these paleogeographic regions. Since the North Pacific region formed its own paleobiogeographic realm by the late Early Cretaceous, it is necessary to develop a standard ammonite zonation for this region, and to establish a relative biochronological time scale and coordinate it with that of Western European standard stratigraphy.