Mesophytic floras (Late Triassic-Early Cretaceous) of the Arctic are most complete for the Upper Jurassic and Lower Cretaceous. Late Triassic floras exist in many areas, but Early and Middle Jurassic floras are scarce in the Arctic.

Mesozoic floras of Arctic islands are not isolated from continental ones. Late Triassic floras of Svalbard, Franz Josef Land, and East Greenland are assigned to the European paleofloristic province. The early Liassic flora of East Greenland is also included in the European province. Early Liassic floras in the areas of the Kolyma and Vilyuy Rivers are assigned to the Siberian paleofloristic province, but a separate Kolyma province is postulated. Late Jurassic floras traceable from the Lena River basin to the Kolyma River basin are typical of the Siberian region. Early Cretaceous floras of most of the Arctic, except West Greenland, belong to the Siberian paleofloristic region. The West Greenland flora belongs to the Indo-European region. Presence of Late Triassic floras on both the con inent and the Arctic islands, in and between marine deposits, suggests unstable marine conditions. Floral similarity indicates a possible land connection between Svalbard and East Greenland and Western Europe in Late Triassic time. East Greenland was undoubtedly connected with Western Europe in Early Jurassic time also.

Late Triassic floras of Svalbard and the Aldan River area indicate warm and rather humid climatic conditions, and a hot climate existed in East Greenland in the Early Jurassic. A Siberian temperate flora apparently formed in the Vilyuy depression and the southern Yakutsk basin in Early Jurassic time. This flora spread during Middle and Late Jurassic time, and in the Early Cretaceous it flourished in vast areas of the Arctic and Subarctic regions.