Radiolarian paleobiogeography in the late Albian–Santonian

Radiolarian paleobiogeography for the late Albian–Santonian is proposed for the first time. The paleobiogeographic differentiation is found to be different for the Albian, Cenomanian, Turonian, and Coniacian–Santonian. The Tethyan and Boreal superrealms can be recognized for the Albian–Santonian. For the Albian–Santonian, the Tethyan Superrealm can be subdivided into realms: Atlantic-Mediterranean, Carpathian-Caucasian, and Tropical-Pacific. The boundaries of these realms changed throughout geological time. The Boreal Superrealm recognized for the Albian so far cannot be subdivided into realms, whereas in the Cenomanian it included the East European and Western Siberian realms without a clear definition of the boundaries and the Boreal-Pacific (in the North Pacific). The Boreal Superrealm is subdivided in the Turonian into two realms (European-Western Siberian and Boreal-Pacific), and in the Coniacian–Santonian, it is subdivided into three realms (European, Western Siberian, and Boreal-Pacific). The Austral Superrealm can be recognized only for the Albian and Cenomanian, and because of the lack of data, it cannot be delineated for the Turonian and Coniacian–Santonian.