This book presents important new evidence about the key period of evolutionary diversification in the Early Cretaceous, based on new or poorly known material from Russia, the Caucasus, Azerbaijan, Dagestan, Kazakhstan, Ukraine, the North Sea, and North Africa. The origin and early development of the group in the Jurassic is reviewed which, together with the new knowledge of Early Cretaceous planktonic foraminifera, sets the scene for the well-known Late Cretaceous to recent evolutionary history of the group.