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The evolution of plants

A concise report of the development of the flora

III. Permian - Early Cretaceous

Plant evolutionI. Silurian and Devonian
II. Carboniferous and Early Permian
IV. Cretaceous - present

Red Permian sedimentsIn the Early Permian circumstances changed. It was getting hotter and dryer and as a consequence large areas turned into desert. The red colour of many soils, formed in this period, reflects the hot, dry climate. Click on the photo on the left. This development is related to the fact that all continents were slowly drifted together and formed one supercontinent (Pangea). This caused an enormous inner land with an extreme and arid climate. That is the reason why many plant species which could resist heat and aridity came into existance. And animal predation! For amphibians and reptiles, being the masters of the continents at that time, consumed everything they met and as a reaction plants developed different defences like thorns and poison.

The division in Paleozoic, Mesozoic and Kenozoic cannot in fact be used for plants. There is an other one for the development of the flora: Paleophytic (Silurian - Early Permian), Mesophytic (Early Permian - Jurassic) and Kenophytic (Early Cretaceous - present). See scheme.
Autinia conferta The seed ferns were still going strong, even until the Jurassic. Many groups disappeared but they were replaced by other ones. In a quarry near Lodève  in France (click photo on the right) many fossil plants from the Lower Permian have been found. Their preservation however is not as good as those from the coal swamps. The reason is that these plants were transported from other places by rivers and this transport often caused heavy damage to the plants. Click on the photo on the left to see some fossils of seed ferns. Click here for extensive information on the quarry of Lodève. Quarry La Tuilière

The clubmoss trees and the horsetail trees disappeared gradually and became extinct during the Permian. The herbal clubmosses and horsetails however lived on, but as a kind of relics of groups which were much more successful in earlier times.
Walchia piniformis The conifers developed strongly, like the Walchia (click photo on the left), resembling very much the Norfolk Island pine. This plant is a relative of the Araucaria, which can often be seen in gardens nowadays. The conifers had their first appearance in the Late Carboniferous, but they became common, and sometimes even dominant, in the Early Permian.
Furthermore the first cycas-like and ginkgo-like plants came into existance (
click the photo on the right). But not until the Triassic and the Jurassic did they come to full development.
The ferns continued their evolution like they do until now.

Glossopteris The southern part of the supercontinent Pangea, composed of Africa, Australia, Antarctica and India, is called Gondwana or Gondwanaland. During the Permian a specific flora evolved here, which has not yet been understood completely. The plants are indicated as Glossopteris and most probably they were seed ferns. But other plants could be included as well.
Glossopteris plants were trees with elongated leaves with reticulate veins. On the leaves are sometimes fructifications. During the Triassic there were still Glossopteris plants, but after that they became extinct. Click on the photo on the left to see some leaves.

At the end of the Permian the greatest extinction of all times took place, meaning the end of 95% of all animal species. The damage in the flora was less extensive, although also many plant species disappeared, but they were soon replaced by other species. As for the plants the Permian passed rather smoothly into the Triassic.
Plant fossils from the Permian are found (among other places) in Germany in Rheinland/Pfalz near Sobernheim, and also in Thüringen near Manebach. Furthermore in France near Lodève.
Equisetites arenaceus Triassic plant fossils are rather scarse in western Europe. The conditions for life were probably very bad in the first ten million years of the Triassic because of an atmosphere poisened by vulcanic gasses. In the Alsace (Fr) Triassic plants have been found, especially conifers. The Upper Triassic, also called Keuper, has yielded very good finding places in Germany. The flora was there dominated by horsetails, but other groups were also present, like ferns, seed ferns, conifers, cycads and ginkgos. Important developments were the appearance of the modern ferns and of the Bennettitales (see below). The book 'Keuperpflanzen' by Kelber and Hansch pictures this flora in a beautiful way. Click on the photo on the left. Near Unternschreez (Bayreuth) one can find fossils from the uppermost part of the Triassic. Click on the photo on the right. Conifer twig from the Rhaetian

In the warm Jurassic period flora and fauna came to full prosperity again. The growing conditions were very good all over the Earth and an abundant vegetation developed. The looks of the forests had become totally different from those of the Carboniferous. Now the gymnosperms were dominating.
Jurassic forest In the first place there were the conifers in many different forms. Then the Araucaria's with their regularly spaced whorls of branches and their very stiff, scalelike leaves, preventing animals to eat them. They are popular garden trees at the moment. Click on the photo on the left to see them. Furthermore there were many species of Ginkgo, also a lane and garden tree nowadays. The Ginkgo, with its characteristic triangular leaves, is a real living fossil. In Yorkshire fossil leaves of the Ginkgo are found resembling very much the only extant species. Click the photo on the right. Fossil leaf of Ginkgo

Cycads An important part of the Jurassic flora was made up by Cycas-like plants with their fronds resembling palm leaves. A group of plants evolved which looked very much like cycads, but in fact being very different from them. They even 'invented' the first flowers! The name of this group is Bennettitales (there is no English name for it; click the pictures on the left en on the right). During many years they have been thought to be ancestors of the modern flowering plants, but this has appeared not to be true. This group of plants has become totally extinct. The real cycads are a kind of living fossils. Zamites sp.

In the Early Jurassic some seed ferns still existed, but later on they died out. The real ferns formed an important element of the Jurassic flora. There were tree ferns as well as herbal ferns. Several groups, living in the Jurassic, have still representatives in de modern flora, but the species are of course different. All Jurassic species have become extinct.
Beach near Whitby Occurrences of Jurassic plant fossils are not common at all. The most important ones are situated along the coast of Yorkshire in England. Furthermore there are places near Bayreuth in Germany. The photo on the left shows the cliffs near Whitby in Yorkshire, where Jurassic plants have been found.
On the right a reconstruction of the forest, crowded with dinosaurs: conifers, araucarias, cycads, bennettitaleans and ferns. Little variation in colour: green in many kinds. No flowers to brighten up the forest.
Jurassic forest

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