Ancient Australian species of plants and animals
In this chapter:
Ancient Australian species of plants and animals
The first plants in Australia were algae
The oldest Australian land plant is called Cooksonia
The Australian continent became cooler and drier
Large ancient animals sometimes are referred to as Megafauna
Australian marsupials originally came from North and South America
This chapter looks at the ancient plants and animals of Australia. It discusses the Australian climate and some ancient, native, now-extinct 'super-beasts' called megafauna.
The first Australian plants
The first plants in Australia, like everywhere else in the world, were algae. For millions of years they grew on the edges of lagoons, lakes and swamps. Remnants of these dead algae formed the first soil. Some algae learned to survive on the rocky, ocean shores. Millions of years later, they evolved into land plant species. Even though these first land plants did not live in water all the time, they still looked very similar to their ancestors, algae.
The oldest Australian land plant is called Cooksonia. Some species of Cooksonia have evolved to become modern forms of mosses. Other Cooksonia species led to the evolution of other plant groups that evolved in Australia later.
Cooksonia had a stem and some spores on top of it. It did not have any leaves, roots, flowers or seeds. Its stems were connected to the soil by rhizoids. Fossils of Cooksonia, which are about 415 million years old, have been found near Mudgee and Broken Hill in New South Wales. Cooksonia fossils were also found in other parts of the world which means that it grew in the time of the super continent, Pangaea.
Baragwanathia is another ancient Australian plant. It descended from Cooksonia and later also led to the evolution of different types of mosses. Baragwanathia itself looked like a giant club moss. It had branched, tall stems. Baragwanathia is the earliest known plant with proper leaves.
The first Australian forests
As the Australian continent drifted away from Gondwana its climate became cooler and drier. Some plants could not survive the new conditions and went extinct. Other plants, like ferns, adapted to the new climate, forming luscious forests. Many fossilised leaves found today suggest that the ancient plants, Glossopterids, lost their leaves in autumn and grew new ones in spring. This type of plant is called deciduous.
Different kinds of conifers, ginkgos and tree ferns evolved in Australia during the Triassic period. Cycads, Sago palms and Kauri pines followed. For example, the Wollemi Pine can still be found today in some areas of Australia. Sometimes it is also called the Dinosaur Tree because it has been around for millions of years. The first flowering plants, like magnolias and buttercups, appeared later - during the Tertiary period.
The first Australian land animals
Land animals evolved with the changing climate. When plants began to grow on land, the volume of oxygen in the air increased as a result of photosynthesis. Animals could then move from the water to the much-friendlier land and adapt to the new way of breathing.
Among the first Australian animals that moved to dry land were Eurypterids. They looked like modern scorpions. They lived in fresh water in the lakes and swamps. Their bodies and legs were jointed. They ate fish, or each other.
The fossilised tracks of Eurypterids can still be found today in some regions. They are the oldest tracks known to be made by animals. Other animals that left the ocean around that time were earthworms, leeches, snails and slugs. Gradually, other land species evolved.
Labyrinthodonts were also among the first Australian land animals. They belonged to the class, amphibia, and looked like large lizards. Like frogs, they had to lay their eggs in water. They had sharp teeth and probably ate fish and other smaller animals. They swam well but were quiet clumsy on dry land.
After dinosaurs and some other reptiles went extinct, mammals started to take over the animal kingdom. Diprotodont was the largest marsupial that ever lived on Earth. It was nearly three metres long and about two metres high at the shoulder. A diprotodont resembled a rhino without a horn. Its feet turned inwards like a wombat's, giving it a pigeon-toed appearance. It had strong claws on its front feet, so it may have been able to dig up roots to eat.
Procoptodon goliah was the largest leaf-eating ancient form of kangaroo. It weighed approximately 200 kg. It could stand on tiptoe and on its tail and reach leaves that were high up from the ground.
Palorchestes Azael was another giant, ancient kangaroo. As more fossils of this species were found, scientists discovered that it must have walked on four legs. Palorchestes may also have had a small trunk. That is why it is also called a marsupial tapir.
Thylacoleo carnifex is usually called the marsupial lion. It probably had a cat-like head with large teeth. It also had claws and very strong paws which made Thylacoleo carnifex a fearsome predator of the ancient Australian forests.
All these large ancient animals are sometimes referred to as megafauna. Megafauna species became extinct about 10 000 years ago. Today, there are different theories about why megafauna went extinct. Some scientists think that early humans killed them all for food. Another group of scientists think that the drastic climate change was the main reason of their extinction.
Marsupials are mammals whose females carry their young in an external pouch. Scientists believe that unique Australian marsupials originally came from North and South America. It is thought that they came through Antarctica when all the continents were joined. Plant fossils found on all the southern continents prove that all the modern continents used to be part of one large land.
Like all continents, Australia is still moving very slowly. Some day, in about 60 million years, it will collide with the mainland of Asia and form a really large mountain range in between.