Discovery of the Heteromorph Ammonoid Amapondella amapondense in the Middle Campanian of Hokkaido, Japan

Abstract. The discovery of the heteromorph ammonoid Amapondella amapondense (van Hoepen) in the lower middle Campanian in the Urakawa, Biratori and Hidaka areas of Hokkaido, northern Japan, represents the first report of this taxon in the Northwest Pacific region. Because the species flourished in other regions during Santonian to early Campanian time, its final geographic occurrence in Hokkaido suggests that global environmental changes likely had a significant influence on ammonoid biogeography during early middle Campanian time.