Mary Cairncross Scenic Reserve

The Diorama

Rainforests Through Time

This diorama shows only a small but representative section of the history of the Australian rainforests. Although there is reference to the Sunshine Coast area and Maleny, the display is intended to give a general picture of prehistoric Australia, as there are insufficient local fossils to give a totally accurate picture.

Within such a small area it is impossible to tell the whole story of Australian rainforests so the display starts at the beginning of the Cretaceous period, 144 mya (million years ago). However, it is Diorama dinosaurworthwhile noting other geological events that occurred in the Sunshine Coast area. The area has always been close to the edge of the continent and close to the sea. The first events of importance that occurred in the area, when the foundations of the rainforest were occurring, were the massive eruptions that formed the North Arm Volcanics during the Triassic period (245-208mya). These massive eruptions laid down thick layers of ash, in some areas up to 900 metres thick. These volcanoes were close to the edges of vast freshwater lakes, for example Lake Walloon, which was one of the largest freshwater lakes ever formed. Erosion of these ash deposits into the lakes in the late Triassic and Jurassic periods (208-144mya) formed the thick sediments of the Landsborough sandstones, a feature of the flat coastal plains that can be seen from Mary Cairncross. During the Triassic and Jurassic periods, the cycads and southern pines, such as the podocarps and araucarians, first appeared. Some other plants such as the ferns had appeared much earlier.

EARLY CRETACEOUS - 144-95mya

During this period, that part of the supercontinent Gondwana which was to become Australia was very close to the South Pole and was subject to the same dark winters and "midnight sun" conditions as the present polar regions. Despite this, the climate was temperate, although snow probably fell during the winter.

Plants

The background picture in the diorama gives an idea of the forests of the time, with widely spaced conifers to intercept most light from the low sun angle and a shrubby understorey. The conifers would have included close relatives of the modern bunya pine (Araucaria bidwillii), hoop pine (Araucaria cunninghamii), kauri (Agathis spp.), Wollemi Pine (Wollemia nobilis) , plum pine (Podocarpus elatus) and maidenhair tree (Gingko biloba). The understorey consisted of small conifers, ferns and their relatives, and cycads. An interesting plant in the foreground is a lycopod (Lycopodium cernuum) which looks like a small pine tree. Up until the end of the Permian period (245mya), these were dominant plants on earth, forming large trees, but have now shrunk to herb size. The very first flowering plants are found in this period.

Animals

The largest dinosaur shown is a pair of Muttaburrasaurus langdoni, a large herbivorous dinosaur of the group called iguanadontids which was found near Muttaburra in Queensland. Also present is the armoured anklyosaur Minmi paravertebra, another herbivore growing to 4m. A cast of the skull of Minmi is in our fossil display. In the front of the display is the small hypsilophodont dinosaur Leaellynnosaura amicagraphica. This dinosaur was found at the Dinosaur Cove site in Victoria. It is thought that its large eyes may have been an adaptation to low light to allow it to keep active during the long polar night. Hidden behind Leaellynnosaura is the small shrew-like Ausktrinosphenos nyktos which is unusual in Australia, in that it appears to be a placental mammal, not a marsupial. Mammals appeared at around the same time as dinosaurs but remained small until the extinction of the large dinosaurs at the end of the Cretaceous period.

LATE CRETACEOUS - 95-66.4 mya

The climate was still temperate although humid. Dinosaurs were still present as evidenced by the famous Winton tracks, which show small herbivorous dinosaurs as well as a large carnivorous dinosaur similar to Tyrannosaurus, but there are few actual fossils.

Plants

This period was the time of the great development of flowering plants. Although conifers were still dominant, species present in the modern rainforest were also occurring, including the Proteaceae, the southern beeches (Nothofagus) and the pepperbushes (Winteraceae). In the diorama, a red-flowered member of the Proteaceae, similar to the modern Australian tree waratah (Alloxylon) and the Chilean Fire Bush (Embrothium) can be seen. Macadamia is another primitive Proteaceae which was also present. Southern beech and the Bolwarra (Eupomatia laurina) can also be seen.

Animals

As already stated, there are few fossils of this era. We have chosen to illustrate a primitive platypus similar to the earlier Steropodon, as platypus were present both before and after this period.

At the end of the Cretaceous period most large land animals became extinct, paving the way for the rise of the mammals. While dinosaurs became extinct, their descendants, the birds, are still with us. This great extinction is linked to a large meteor that hit the Earth to form the Gulf of Mexico and it is thought that the southern lands on the opposite side of the globe were critical to the survival of life. It is also thought that the dinosaurs as a group were declining before this final catastrophe, perhaps because of massive world-wide volcanism during this period.

LATE OLIGOCENE-EARLY MIOCENE- 25-20mya

The Oligocene (45-23.7mya) and Miocene (23.7-5mya) were times of great diversity and change on the Australian continent. At the start of this period the whole of Australia was covered by rainforest. By the end of the Miocence period, the rainforest had shrunk and the pattern of sclerophyll forest and grassland had already emerged, although they were not as dominant as they are today. The diorama shows a snapshot of this period from 25-20mya during a period when the Glasshouse Mountains were active volcanoes. The rainforests of Mary Cairncross are growing on lava flows from this period.

Plants

The rainforests of this time would have appeared similar to those of today. Southern beech and some of the araucarians would have been more dominant, but nothing about  the plants would have been strange to a modern observer other than to a botanist.

Animals

We are able to reconstruct the general appearance of the animals by comparison to modern examples, but there must be a great deal of speculation about soft tissue. The artist has demonstrated this by making her Miocene cockatoo multi-coloured. Other birds present were similar to the modern logrunner and owlet nightjar. The first animal to be seen is a tiny primitive pygmy possum which originated somewhere in the Eocene (57-45mya). This is similar to pygmy possums found in both South America and Australia. On the ground, the horned turtle Meiolania is only a baby. This ancient group disappeared only 100 000 years ago, and grew to a length of 2m. The predator Wakaleo at the waterfall is one of the early marsupial lions, a fierce predator which was closely related to possums. Although a joey is shown in the pouch to show its marsupial nature, no-one can be sure whether the pouch was actually forward or backward facing or poorly developed such as in the modern quoll. The baby Palorchestes leaning against the trunk is a member of the herbivorous megafauna. The small trunk is once again speculation based on the skeleton. As in modern rainforests overseas, the rainforest animals were generally smaller than their later open land cousins. The ziphodont crocodile in the background is a land crocodile, one of a group which were more terrestrial in their habits than modern crocodiles. The frogs and skinks around the waterfall are modern, but very similar animals were present during this period.

MODERN RAINFORESTS

This part of the diorama shows the transition from the wetter tropical rainforest and wet sclerophyll forests of the coast to the drier types further inland and on poorer soils. These types contain more bunya and hoop pine as well as species such as the python tree (Austromyrtus bidwillii) and the Queensland bottle tree (Brachychiton rupestris) and its relatives like lacebark (Brachychiton discolor). Other types of rainforest such as warm temperate, cool temperate, tropical and monsoon are not shown.

Animals

The rainforest specialist red-legged pademelon is shown, as well as the whiptail wallaby which seems to enjoy the areas that contain a mixture of dry rainforest and open areas. Look for the spiny crayfish on the forest floor. These are the very restricted Mountain freshwater crayfish (Euastacus urospinosus) which live in burrows going down to the watertable and forages on the forest floor at night. It enters the stream only in summer to breed. Also visible are a noisy pitta, a common tree snake and a carpet python. A brush turkey is on the buttress.

DRYING OUT

Although this area is part of the diorama, it should be treated as a separate section. It shows the ultimate changes which occurred to much of Australia's forests with climate changes and human influences. Some of the plains megafauna survived until about 26 000 years ago or, according to some tantalising evidence, even later. It is certain that humans, the hunters were part of the process. The Thylacine is a reminder that European people removed a significant remnant of Ancient Australia as recently as the 1930s.

Bibliography

Archer M., et al. (1991) Riversleigh. Reed Books: Balgowlah
Laseron C., Brunnschweiler R.O (1984) Ancient Australia. Angus & Robertson: Sydney
Long J. A. (1998) Dinosaurs of Australia and New Zealand. UNSW Press:Sydney
Stevens N. C. (1984) Queensland Field Geology Guide. Geological Society of Australia: Brisbane
Rich T. H., Vickers-Rich P. (2000) Dinosaurs of Darkness. Allen @ Unwin: Sydney
Rich T. H., Vickers-Rich P. (1993) Wildlife of Gondwana. Reed: Sydney
White M. E. (1998) The Greening of Gondwana. Kangaroo Press: Sydney
White M. E. (1994) After the Greening. Kangaroo Press: Sydney

 

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