Taxonomists began to think of having their classification systems reflect evolutionary relationships. This is sometimes very difficult as it may conflict with the need for an easily referable classification. Oldest angiosperm fossils are about 125 million years old Angiosperm fossils are rare, it has been proposed that early angiosperms evolved in the hills and uplands of the tropics where fossilization does not occur. So, if this is true, we have no way of knowing what the earliest angiosperms looked like. Once angiosperms moved into the lowlands, fossilization occurred and we do have some records of these plants.
Angiosperms are clearly the most successful group of land plants.
Tough leaves resistant to drought and cold. Precise systems of pollination and seed dispersal 2. Deciduous - enables plant to survive times when water is not available, especially imporant in cold climates 3. Enormous chemical diversity provides protection from herbivores 4. Evolution of herbaceous perennials and annuals.