Postcards from the Mesozoic: Forest landscapes with giant flowering trees, enigmatic seed ferns, and other naked-seed plants

Abstract

Earth’s vegetation during the 186 million years of the Mesozoic, from the Paleogene–Cretaceous boundary at 66 million years ago back to the Triassic–Permian boundary at 252 million years ago, was filled with forests. Like today, the forest was the dominant terrestrial ecosystem. The trees that created the forest habitat, along with the other woody plants and ferns in the understory and groundcover, were the primary producers that powered Earth’s ecosystems by converting sunlight into chemical energy through photosynthesis. Yet, the forests that flourished during the Mesozoic differed from those found on Earth today. The Mesozoic climate was generally warmer, with milder seasons, a higher sea level, and no polar ice. This resulted in evergreen forests that may have looked superficially similar to gymnosperm-dominated forests of today, but were made up of very different kinds of plants. This is because major evolutionary changes took place in the plant world during this time interval. The Cretaceous witnessed the emergence and diversification of the flowering plants, which define our global flora now. In contrast, the Jurassic and Triassic floras were dominated by gymnosperms such as conifers and cycads, as well as by other, enigmatic, naked-seed plants including seed ferns and bennettitaleans that are now extinct. Continental drift tore landmasses apart, separating Northern Hemisphere floras with ginkgoes from the Gondwana flora in the south, which also is now extinct. Geological time, biotic evolution, and plate tectonics all contributed to the making of paleobotanically unique forests in different parts of the world. In this chapter, we present a series of written postcards from the Mesozoic, each one describing a forested landscape, as we travel back in time together on a virtual plant safari.