Australia's changing climate shaped the evolution of kangaroos, a new study has claimed.
In the first anatomical study of the entire skeletons of modern and fossil species, an international team, led by Flinders University, has pieced together the most reliable and detailed kangaroo family tree to date.
Their findings have shown how the abundance and diversity of macropods -- including kangaroos and wallabies --matches the spread of woodlands and grasslands in Australia as forests retreated to the coast over millions of years.
Dr Gavin Prideaux, who led the study, said: "Kangaroos and wallabies have long been recognised as potentially ideal barometers of historical climatic change in Australia.
"They 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 scientists established that while early forms were adapted to the abundant soft-leaved forest plants, but later macropods had to adapt to more arid conditions.
"We see clear changes through time in teeth and skull shape that reflect diets of tough leaves and grasses, and parallel changes in foot anatomy that reflect an improved ability to hop longer distances through more open habitats," he said.
The scientists argue that the Macropus lineage, which contains the red and grey kangaroos and some wallabies, represents the peak of marsupial evolution.
"Macropus has been around for four million years and has more living and extinct species than any other marsupial genus. They're a great Australian success story," Dr Prideaux said.
The study also confirms previous DNA evidence about the relationships of the highly endangered merrnine, a small wallaby restricted to two tiny Western Australian islands, the scientists say.
"The merrnine is the sole living survivor of a unique branch of the macropod evolutionary tree that split off around 20 million years ago, but we know very little about the animal. While its conservation is a priority, studies of its biology should teach us a lot about the formative steps in macropod evolution," Dr Prideaux said.
The findings have been published in the 'Zoological Journal of the Linnean Society'.