Studies of Mesozoic plants have for a long time centered on Europe, where every Mesozoic flora was regarded as a world standard, such as the Yorkshire flora. Studies of the Mesozoic plants and floras of the circum-Pacific regions have advanced rapidly during the past three decades, and many new data are now available. Representative specimens are illustrated in Plates 96–98.
In Japan, Mesozoic plants are generally abundant, though not throughout the section, and they occur mostly in marine strata or in plant beds sandwiched between marine beds (Kimura 1987, 1988). Elsewhere in the Pacific region, Mesozoic plant beds are nonmarine and thus difficult to date precisely. In most Mesozoic plant assemblages of Japan the details of reproductive organs of ferns and cuticles of gymnosperms have been lost because of tectonic and repeated igneous activities. Most Mesozoic floras of Japan, of every period and stage, may nevertheless be regarded as the most important ones in the Pacific.
In this chapter, Kimura reviews the current status of the Japanese Jurassic floras and that of coeval floras in other cirum- Pacific regions, and Lebedev, Markovich, and Samylina review the Jurassic floras in the Pacific sector of Russia.
Early Jurassic plants are known from the Higashinagano Formation and the lower part of Shizugawa Group, but they are rare and insignificant (Figure 18.1).