Dinosaurs more than a bunch of old bones

Dinosaurs more than a bunch of old bones

22 Jul 2009

ben-kearDr Ben Kear
Email: b.kear@latrobe.edu.au

Three new dinosaurs were recently announced in Australia, and the resulting international publicity storm is a clear indication of the enduring public interest in fossils and the history of life on Earth.

But beyond the popular imagery of fantastic 'real-life' monsters, little attention is paid to the important contribution that palaeontology − the study of fossils and ancient environments − can have for our fundamental understanding of current problems such as species extinction and climate change.

Australia's spectacular chronicle of animals and plants from the Age of Dinosaurs has proven particularly significant in this regard: it records a time when our continent was on the southern polar circle, and witnessed both extinction and the genesis of 'modern' life on the back of rapid climatic warming about 100 million years ago.

During the latter part of the Age of Dinosaurs (formally termed the Cretaceous Period) Australia was attached to Antarctica and formed the eastern extremity of an immense landmass straddling the South Pole. Evidence of ancient climates tells us that conditions were generally quite moist, with distinct seasons and annual winter temperature drops well below freezing. Permafrost, glaciers and even sea ice seem to have been present for at least part of the year, and because of the very high-latitude, we can infer that periods of extended polar darkness blotted out the sun for months on end.

The discovery that ancient Australia experienced such extreme environments has come as something of a surprise because the common view of the 'Age of Dinosaurs' is that it was a time of constant warm conditions all around the globe. New interpretations suggests that cyclical temperature fluctuations once affected southern polar Australia in much the same way as the famous 'Ice Ages' impacted on the northern hemisphere in more recent geological history.

As the climate changed, so did the animals and plants that lived in it. The fossil record show that Australia's Cretaceous polar faunas and floras either adapted or became extinct, including the replacement of apparently cold-adapted archaic relics such as the last temnospondyl amphibians (giant salamander-like predators) and some plesiosaurs (marine reptiles resembling the popular image of the Loch Ness monster) by ancestors of modern 'warm-weather specialists' like crocodiles and sea turtles. In addition, many important elements of our current Australian natives such as flowering plants, platypus-like monotremes, lungfish and even some non-marine snails underwent substantial change and expansion in response to Late Cretaceous global warming.

Even from this brief account it is evident that Australia's Age of Dinosaurs has an important scientific legacy beyond the accumulation of dust on skeletons in museums. It is now clear that detailed documentation of this country’s broader palaeontological history is critical for a better understanding current environments and biodiversity. Knowledge of faunal/floral evolution, past radiations and extinction events are especially relevant given the catastrophic rate of environmental degradation and the rate of extinction now occurring because of human activities and habitat disturbance.

It is only by examining the causes of extinction and adaptation in the past that we can ever hope to understand how organisms respond to climate change, and provide important clues on how to deal with these critical problem in the future.

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