Giant kangaroos, marsupial lions and wombats the size of a car survived all that climate change could throw at them but were wiped out by the arrival of mankind, according to a study.

Fossil remains of the animals were found in a cave on the Nullarbor Plain, in southern Australia, and scientists have been astonished by the number and variety of creatures preserved.

At least 69 species of mammals, birds and reptiles, a third of them now extinct, have been unearthed at the site after falling and becoming trapped in the deep caves 400,000 to 800,000 years ago.

Among the hundreds of fossils were giant kangaroos that weighed 31½st (200kg) and stood 10ft (3m) high, and the first complete skeletons of Thy-lacoleo carnifex, the marsupial lion. Eight kangaroo species previously unknown to science were uncovered at the Thylacoleo caves, including two that lived only in woodland, and a giant bird, Leipoa gallinacea.

It had previously been assumed that for the land to support such a range of large animals it would have to have been wet enough to sustain woodland and lush vegetation of a type that is absent from the arid Nullarbor Plain today.

Analysis of the remains, however, has revealed that the climate when the animals died was just as dry as it is now — and yet it supported far more vegetation.

The finding, reported in the journal Nature, means that palaeontologists must rewrite theories on Australia’s environmental history that has hitherto held Ice Age-driven climate change to be the cause of the animals’ extinction.

Gavin Prideaux, of the Western Australian Museum, who led the study, said that the richness and detail of the fossils was the palaeontological equi-valent of the Rosetta Stone.

Rather than climate change drying out the landscape and killing all but the hardiest plants, the researchers point the finger of blame at the arrival of Man on the continent 50,000 years ago.

Previous research has suggested that Man chose to alter the environment by starting bushfires to burn down un- wanted trees and plants.

Scientists now believe that these bushfires changed the landscape so radically that large herbivores no longer had enough vegetation. When they died out, so did the carnivores that preyed on them.

The research leader, Professor Richard Roberts, of the University of Wollongong, said that the animals had survived repeated climate change yet had disappeared suddenly in the past 50,000 years.

“Suddenly and during quite pleasant climatic conditions when the megafauna should have thrived, they went extinct. Why? The only new ingredient in the mix at that time was humans,” he said.

“Humans very likely played the decisive role in the extinction event through hunting of juveniles, burning of the vegetation cover and changing the plant composition to disadvantage the browsers and grazers.”

Fossils were first found at the caves in 2002 and although hundreds have been found by a series of expeditions, many more are expected to be dug up in the coming years.

They are adding unpredented detail to scientific understanding of what Australia was like during the Pleistocene era, 1.8 million to 11,500 years ago.

Professor Roberts said: “Just think what a fascinating place Australia would have been as recently as 50,000 years ago, with different plants and all those giant herbivores and carnivores roaming the landscape.”

Professor John Long, of MuseumVictoria, who led three expeditions to the caves, said: “To find complete, undamaged skeletons of Australia’s largest predatory marsupial, Thylacoleo, was a dream come true.

“But it got much better when we realised that there was a diverse fauna of many other other long lost megafauna within the cave deposits. The fauna is extraordinarily diverse.”

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