Australian Dinosaur Story
Environment in which dinosaurs lived
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| Dinosaur environment. |
Was the climate in the Age of Dinosaurs similar to that of today?
No. The Earth's climate has varied greatly throughout time. At some stages in the Earth's history, the climate was very cold, resulting in Ice Ages. At other times the climate was quite warm. For much of the Mesozoic Era (the Age of Dinosaurs), parts of Australia would have experienced a colder and wetter climate than we have at present, due largely to the more southern location of the Australian continent.
How does this climate change affect the Earth?
For many millions of years, the primary drivers of climate change
have been the positioning of the continents, mountain and ocean
building as a result of continental drift, and continent building
resulting from volcanic activity. As the climate changed over time,
so too did the environment and the types of animals and plants it
could support.
During the Mesozoic Era, the large land area (see The break up of
Pangaea animation) and the position of the continents and major
mountain ranges were the primary factors in the change of both sea
levels and climate.
What climate did Australia's dinosaurs live in during the Cretaceous Period?
When the Cretaceous Period began, about 140 million years ago, Australia
had a cool, temperate climate that was very gradually warming as
the continent began to move away from the South Pole. The landscape
was dominated by conifers, pines and ferns as well as some of the
first flowering plants. Australia's proximity to the South Pole
would have resulted in lower levels of light and a landscape similar
to that of a woodland environment.
Much of Australia (about half) was covered by shallow inland seas,
dividing the land into a number of large islands. Today this same
area is called the Great Artesian Basin.
Why do scientists think this big sea existed?
Layers of rock from the Cretaceous Period in the Great Artesian Basin contain many fossils of marine (sea) dwelling animals, proving the area was once covered by the sea. These animals included some very large reptiles such as the plesiosaurs, ichthyosaurs, and crocodiles. You may like to investigate these animal groups.
Were any of these marine animals dinosaurs?
No. The dinosaurs were all terrestrial (land-dwelling) animals.
What other animals and plants lived in the Cretaceous?
Other important Cretaceous marine animals included the Ammonites
and Belemnites (both shelled animals related to present day
squid), and starfish and shellfish. On land there were insects,
mammals, and a great many flying reptiles known as Pterosaurs
(these are not classed as dinosaurs). Mammals were very small
at that time, and relatively unimportant. Mammals only flourished
after the dinosaurs became extinct.
There were also birds in the Cretaceous. In Australia, bones
of early species of birds have been found in Queensland, and
at Koonwarra in Victoria, the oldest known feather of a Passerine
(an order of bird species) was found. Some scientists believe
that birds may have evolved from one of the dinosaur groups.
Plants included forests of tall conifers, ginkgos and cycads,
with an undergrowth of ferns. Flowering plants began to evolve
quite early in the Cretaceous while grasses did not evolve
until later in the period.
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| Ammonite | Belemnite | Pterosaur |
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| Conifer | Ginkgo | Fern |
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| Cycad | Mossy undergrowth |
Do any of these animal and plant species exist today?
Yes. While many species became extinct at the end of the Cretaceous Period, some animals and plants have survived with very little change right up to the present day. The Australian Lungfish, found in the rivers of eastern Australia is a true Mesozoic survivor. It is almost impossible to tell it apart from the fossil remains of Lungfish from the Cretaceous, making it a 'living fossil'. The Wollemi Pine found in canyon forest near the Blue Mountains, New South Wales can be traced back around 40 million years ago and shares similarities with some fossils from the Cretaceous.
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| Lungfish |
Was the climate consistent throughout Australia at that time?
No. Australia's climate was cool to temperate during the Cretaceous and, although the climate gradually warmed throughout the period, the northern parts of Australia may have been somewhat warmer than the southern parts, which were close to the South Pole. Australia was still joined to Antarctica during the Cretaceous, but even so, the conditions would have been more temperate than modern Antarctica. Fossils show that it was mild enough for trees to grow.
Did the same dinosaur species occur all over Australia?
Fossils indicate that northern dinosaurs, such as those found in what is now central Queensland, may have been different from the southern (or 'polar') dinosaurs whose fossils have been found in Victoria. The polar dinosaurs seem to have been smaller and adapted to living in a colder climate.
What did the dinosaurs eat?
Many dinosaurs ate plant stems and leaves. Plant-eating animals are known as herbivores. Other dinosaurs were meat-eaters and these are called carnivores. Still others would have eaten insects (insectivores), and some may have eaten a mixture of plants and animals (omnivores).
How can scientists tell whether a dinosaur was a herbivore or a carnivore?
Scientists can tell a lot from studying fossils. All living things
have special features to help them in the way that they live. Some
examples would be the ability to run fast for a hunting animal,
tough skin and spines for self defence, sharp teeth for a meat-eating
animal, stripes for camouflage, and so on.
The dinosaurs that were carnivores tended to run on their large
hind legs, and had sharp claws to catch their prey. They had needle-like
teeth for tearing flesh. On the other hand, herbivores had teeth
suitable for tearing off and swallowing plants, and did not need
sharp claws. It is likely that the polar dinosaurs had very good
eyesight for finding food in the dark polar winters.