During the whole of the Mesozoic era Japan appears to have lain on or near the margin of the Asiatic continent, and the marine deposits are confined for the most part to the eastern side of the islands.
At the beginning of the Mesozoic era the whole country became land, bearing upon its surface the salt lakes in which the Trias was laid down.
This form of stem, of a habit entirely different from that of recent Cycads and extinct Bennettites, points to the existence in the Mesozoic era of another type of Gymnosperm allied to the Bennettitales of the Jurassic and Cretaceous periods by its flowers, but possessing a distinctive character in its vegetative organs.
The division known as the Cycadophyta is represented by a few living genera of limited geographical range and by a large number of extinct types which in the Mesozoic era (see Palaeobotany: Mesozoic) played a conspicuous part in the vegetation of the world.
The later period of the Mesozoic era saw the almost sudden advent of a fully developed angiospermous vegetation which rapidly occupied the earths surface, and which it is not easy to link on with any that preceded it.
It is interesting to observe, as will be shown later, that during the Mesozoic era there was a land-mass in the north of Asia and another in the south, and between them lay the sea in which ordinary marine sediments were deposited.