During the Jurassic and Early Cretaceous, Arctic seas were linked with the Atlantic and Pacific Oceans. Warm ocean currents penetrated from the Atlantic Ocean, resulting in greater abundance and diffusion of the marine fauna in the Atlantic part of the Arctic; this was especially pronounced during the Late Jurassic. The North Pole, as confirmed by paleomagnetic and paleobiogeographic data, was north of the Bering Strait during the whole Jurassic and Neocomian (earliest Cretaceous).

The marine fauna was only weakly differentiated during the Hettangian, Sinemurian, and early Pliensbachian (Early Jurassic). The Tethyan and Boreal provinces developed; the latter, situated around the pole, was characterized by sparser cephalopod associations and by the appearance of endemic forms (up to the family level) in the benthos. During the late Pliensbachian, faunal differentiation reached the province level. The Boreal region was differentiated into West European and Arctic provinces, which continued to exist during the Toarcian and early Aalenian. During the Middle Jurassic (from late Aalenian time), faunal diversity in the Boreal region increased sharply, with Arctic and North American provinces differentiated within this region. The West European province appears to have xtended beyond the limits of the Boreal region. During the Callovian, Oxfordian, and Kimeridgean (Late Jurassic), the Boreal region again tended to form two subregions: the Arctic region which included the North Siberian, Chukotsk-Canadian, and North American provinces; and the Boreal Atlantic region which included the West European and Urals-Greenland provinces.

During the Volgian (Volzhian) and early Berriasian (latest Jurassic, earliest Cretaceous), the Boreal fauna was more isolated from the Tethyan fauna and constituted a Boreal realm with Arctic and Boreal Atlantic regions. The Arctic region included the North-Siberian, Chukotsk-Canadian (around the Pole), and Boreal Pacific provinces, and the Boreal-Atlantic region consisted of the West European, East-European, and Urals-Greenland provinces. During the late Berriasian, Valanginian, and early Hauterivian (Early Cretaceous) the Arctic region extended westward and included the Trans-Uralian region.

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