The evolution of kangaroos has given a clear picture of Australia's changing climate, according to a new study.
Murdoch University's Dr Natalie Warburton and Dr Gavin Prideaux from Flinders University have analysed changes to the kangaroo skeleton over time which reflect Australia's changing environment and climate.
Dr Warburton said in this way kangaroos represent a sort of barometer for climate change.
"This is important for our understanding of historical climate change in Australia," she said.
"Our study represents the most comprehensive anatomical analysis of the evolution of modern and fossil kangaroos on the basis of the skull, teeth and skeleton – including some of the new fossil species we recently identified from caves on the Nullarbor."
The findings, published this month in the Zoological Journal of the Linnean Society, will be the most reliable and detailed kangaroo family tree to date.
They show how the abundance and diversity of macropods – which includes kangaroos, wallabies and tree-kangaroos – matches the spread of woodlands and grasslands in Australia as forests retreated to the coast over millions of years.
Macropods have been around for at least 30 million years, but difficulties in working out which species are related and when certain lineages evolved have hampered research for more than a century.
By comparing skeletons from 35 living and extinct macropod species, the researchers established that while early forms were adapted to the abundant soft-leaved forest plants, later macropods had to adapt to more arid conditions.
"The skull and teeth give us a good understanding of the sorts of food that was available in the environment," Dr Warburton said.
"The postcranial skeleton, and in particular the feet, give us important clues about how far and fast the animals were moving, which in turn shows us whether the habitat was dense or open."
The study also found that the small, endangered merrnine, or banded-hare wallaby, was much more distantly related to the other kangaroos and wallabies than previously thought.
"The merrnine is actually the sole survivor of an ancient group of kangaroos that separated from the rest of the family around 20 million years ago," said Dr Warburton.
"It's now only found on the islands of Shark Bay in Western Australia – this highlights that conservation for this species is a priority."
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