Caverns Give Up Huge Fossil Haul

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An astonishing collection of fossil animals from southern Australia

is reported by scientists.

The creatures were found in limestone caves under Nullarbor Plain and

date from about 400,000-800,000 years ago.

 

The palaeontological " treasure trove " includes 23 kangaroo species,

eight of which are entirely new to science.

 

Researchers tell Nature magazine that the caves also yielded a

complete specimen of Thylacoleo carnifex, an extinct marsupial lion.

 

It appears the unsuspecting creatures fell to their deaths through

pipes in the dusty plain surface that periodically opened and closed

over millennia.

 

Most of the animals were killed instantly but others initially

survived the 20m drop only to crawl off into rock piles to die from

their injuries or from thirst and starvation.

 

The preservation of many of the specimens was remarkable, said the

Nature paper's lead author, Dr Gavin Prideaux.

 

All shapes

 

" To drop down into these caves and see the Thylacoleo lying there

just as it had died really took my breath away, " the Western

Australian Museum researcher told the BBC's Science In Action

Programme.

 

 

Animals would have fallen through surface holes to their deaths

" Sitting in the darkness next to this skeleton, you really got the

sense of the animal collapsing in a heap and taking its last breath.

It was quite poignant.

 

" Everywhere we looked around the boulder piles, we found more and

more skeletons of a very wide array of creatures. "

 

In total, 69 vertebrate species have been identified in three

chambers the scientists now call the Thylacoleo Caves.

 

These include mammals, birds and reptiles. The kangaroos range from

rat-sized animals to 3m (nearly 10ft) giants.

 

 

Dr Prideaux's team continues to investigate the Nullarbor fossils

 

 

Enlarge Image

 

The team even found an unusual wallaby with large brow ridges.

 

" When we first glanced at the animal, we thought they were horns; but

on closer inspection we realised they must have performed some sort

of protective function, " Dr Prideaux explained.

 

" The beast must have been sticking its head into spiny bushes and

browsing on leaves. "

 

The 'Ancient Dry'

 

The scientists' investigations indicate the ancient Nullarbor

environment was very similar to that of today - an arid landscape

that received little more than 200mm of rainfall a year.

 

What has changed significantly is the vegetation. Whereas the

Thylacoleo Caves' animals would have seen trees on the plain, the

modern landscape is covered in a fire-resistant chenopod shrub.

 

This observation goes to the heart of a key debate in Australian

palaeontology, the team believes.

 

 

The caves and their contents were first discovered in 2002

 

 

More details

 

The continent was once home to a remarkable and distinctive

collection of giant beasts.

 

These megafauna, as researchers like to call them, included an

immense wombat-like animal (Diprotodon optatum) and a 400kg lizard

(Megalania prisca).

 

But all - including the marsupial lion - had disappeared by the end

of the Pleistocene Epoch (11,500 years ago).

 

Some scientists think the significant driver behind these extinctions

was climate change - large shifts in temperature and precipitation.

 

But Dr Prideaux and colleagues argue the Thylacoleo Caves' animals

give the lie to this explanation because they were already living in

an extremely testing environment.

 

" Because these animals were so well adapted to dry conditions, to say

that climate knocked them out just isn't adequate. These animals

survived the very worst nature could throw at them, and they came

through it, " co-author Professor Bert Roberts told BBC News.

 

" If you look at the last four or five glacial cycles, where the ice

ages come and go, the animals certainly suffered but they didn't go

extinct - they suffered but survived, " the University of Wollongong

scientist said.

 

This assessment would be consistent with the other favoured

extinction theory - extermination by humans, either directly by

hunting or indirectly by changing the landscape through burning.