Although it was only till recently that scientific discoveries have proved that the continents have been moving now and in the past. The main theory that supported this theory and caused such a break through for scientists was the continental drift theory. The theory of plate tectonics states that the Earths crust is divided into several big, rigid plates that are made up of continents and ocean basins. These crustal plates move over time, and may slide past or collide with each other. (Diane Alford & Jennifer Hill 2003). Evidence that Australia was once part of Gondwana has been found through the matching of the continental margins that form to fit together to support the theory of Gondwana existing. The fact that fossils have been found in common on Gondwana continents, and present day organisms on Gondwana continents also supports the theory that Australia was attached to the major continent Gondwana.
Taken from “a field guide to Dinosaurs” by H.Gee & Luis V.Rey, PG 22&23
Describe what the climate was like during the selected era and use this information to explain any changes to the flora and fauna in Australia during the era.
The Mesozoic era appeared to have been a warm, humid and arid climate with hardly any change between seasons. Although they were mildly seasonal, there were also areas of mild climate, and forest landscapes as well. Small ferns covered the ground and even though Australia was situated so very close to the South Pole (figure I, II, III) there were no ice poles to make Australia a cold climate. This had a dramatic effect on the climate in which organisms could flourish in the Mesozoic period.
Triassic period: At the beginning of the Triassic period averaged temperatures of about 10 to 15 degrees were estimated to have been the global temperature at the time. Towards the end of the period, the climate began to become drier and hotter. Deserts in large amounts began to occur due to the temperatures in the southern regions of the world. (, Jurassic Art multimedia Encyclopaedia 2003) In Australia particularly, the humid climate and seasonal rainfall created a suitable environment for primitive flora and fauna of the Mesozoic period. Coal accumulated in swampy basins of the Sydney area, and much of the sandstone in the Gosford area dates back to the Triassic age. (J.Long 1998). Flora and fauna had adapted to the conditions of the Triassic Australia. Flora of Australia was very much dominated by ferns, conifers and especially the Dicroidium flora. These types of plant life adapted well to its surroundings in Australia and continued to flourish well into the Jurassic. The fauna of the time was mainly amphibian and fish life. They included deep boned fish and the most primitive known shark species. (J.Long 1998)
Jurassic period: During the Jurassic period rainfall increased and large bodies of water became apparent in areas where land once was. The climate was still hot and dry with little change between seasons, but the vegetation of the time had evolved to contain luscious and rain-forest type plants dominating in all areas that were once desert. Evidence of the vast plant life has been found in large numbers in the widespread coalfields that date from the Jurassic period, therefore supporting the theory of the dominating plant life in the Jurassic. ( Jurassic Art Multimedia Encyclopaedia 2003)
The climate of Australia was indefinitely similar, but also had cold weather forms of plant life living as well. During the Jurassic period the impact of the continents splitting to form Gondwana and Laurasia had influential effects on the climate as shown above as the sea currents began to change their courses. These plate movements had also detrimental effects on fauna. Australia’s thriving invertebrates were not the only life around at the time. Land animals of the age were dinosaurs and roamed Australia as well as the rest of the world. Both aquatic and land dinosaurs have been found in Australia as well as flesh eating types (J.Long 2003)
Cretaceous period: The giant rain forest like areas of the globe began to disappear and during the middle of the period, the climate began to cool dramatically and became both cool and wet. Seasonal rainfall was still apparent, and still their was no Polar ice in the south. There became a greater extreme in temperature between the poles and the equator, varying the climates of the south and northern continents. The earliest angiosperms had appeared and began to diversify, taking over most of the other plant life. (, Geological Society of America 1999) Although Australia’s climate was acting a little differently at this time as it started to break away from Gondwana and the present day India and Antarctica. As water levels rose, great inland seas began to run through the centre of Australia. Although the most predominant plant life was still the conifers and ferns, the first flowering plants had appeared by the early Cretaceous. The earliest evidence of these flowering plants has been found from the Koonwarra site, in Eastern Victoria. (J.Long, 1998) Towards the end of the cretaceous an explosion of life forms began to develop in Cretaceous Australia. Flying reptiles, marine reptiles and the first Australian mammals began to adapt and evolve to Australia’s changing climate.
