When the continents are separated from each other, a large area of each continent is surrounded by low lying land. Some formed shallow bordering seas, other portions became low-lying terrestrial swamps. The latter allowed the diversification of moisture requiring plants like ferns and their relatives. When the continents fused, they formed a massive continent, limiting the total area for low-lying land. Further, if you know anything about climatology, the centers of continents have great extremes of climate both in precipitation and seasonality of temperature - a situation we term a continental climate. With the formation of Pangea, a good portion of the available space of the earth becomes dominated by a continental climate. We see those plants that are moisture demanding, the pteridophytes that rose and radiated in the Paleozoic, go extinct - they disappear. Plants that are better adapted to a drier environment, the seed plants in specific, radiated.

Our poor friends the dicynodonts were largely feeding on the wet-loving plants, which now become rare. We go from a world dominated by nice succulent ferns that you could gently chew, to a world in which such plants still exist, but only in limited areas along stream courses. Now, much of the world is dominated by a much harder, more leathery kind of flora made up of conifers and cycadophytes. One suspects that even these may have been limited by climate, and that many places in the centers of the continents were virtually free of vegetation.

Just think of lapping your tongue around that conifer or a cycad leaf Tough, sclerotic, often spinose, rich in chemicals that inhibit digestion. Indeed, make your students go at some point and pick a leaf of something that you know is reasonably non-toxic like a pine tree (so you don't end up with a lawsuit when they keel over dead from doing this). Tell them to chew the pine needle; it is very strong, resistant, bitter. Those same chemicals that are distasteful also inhibit digestion. In order to get energy out of chewing something like this, you are going to have to chew it a long time. You are going to have chew an awful lot of it. But, this is the kind of vegetation that became the dominant vegetation over the surface of the planet in the early Mesozoic.

Narrative Index

Table of Contents

BioForum Index

AE Partners Collection Index

Activities Exchange Index