Fossils and DNA from living species as well as species that have recently gone extinct indicate endangered Australian Marsupials are significantly older than previously believed. Bandicoot fossils in particular play a critical role in understanding how the unique biodiversity found in Australia responded to past climate changes. What the team of researchers found was that a shift to drier conditions that occurred 5 to 10 million years ago drove ancient species into extinction, while prompting the emergence of modern groups at the same time.
“We used bandicoots as a model to examine the radiation of marsupials relative to climate change through time. Bandicoots are the marsupial equivalents of rodents and rabbits that today occupy a spectrum of desert through to rainforest habitats across Australia, New Guinea and surrounding islands. Alarmingly, however, most bandicoot species are under dire threat of extinction from introduced predators, habitat loss, and human hunting,” says Dr. Benjamin Kear from the Museum of Evolution at Uppsala University, the lead author on the study.
“The evolution of Australia’s mammals has long been linked to aridity. Yet this hypothesis is based upon only a few distinguishing features found in the teeth and skulls of modern species,” Dr. Ken Aplin with the Smithsonian National Museum of Natural History says in the article.
Endemic to Australia and New Guinea, Bandicoots are a group of approximately 20 species of marsupial omnivores. Small to medium sized, the bandicoot belongs to the order Peramelemorphia. The term was originally used to refer to the Indian bandicoot rat, which is not related.
The oldest bandicoot fossils are more than 25 million years old, however, isolated teeth more than 50 million years old suggest a deeper ancestry. By comparison, the first modern bandicoots showed up less than 5 million years ago, while their oldest relatives appeared to have inhabited rainforests approximately 20 million years ago. Lemdubuoryctes aruensis however, the remarkably archaic new bandicoot fossil discovered by Alpin, didn’t live in a rainforest but on an expansive savannah plain stretching from Australia to New Guinea at the time of the last glacial maximum.
“While retreating rainforests and spreading grasslands did provide a backdrop for ecosystem change 5-10 million years ago. The Australian fauna likely adapted via changing its distribution rather than undergoing wholesale extinction and replacement,” Michael Westerman, with La Trobe University in Australia, says in the article, adding, “This agrees with our results from DNA, which indicate that modern desert-living bandicoot groups pre-date the onset of aridity by as much as 40 million years.”
These timeframes coincide with the proliferation of Eucalyptus woodlands in Australia’s interior.
“Bandicoots, like other Australasian marsupials, probably occupied a range of different habitats over many millions of years. However, our study has further implications for future conservation. Arid zone bandicoots are amongst the most vulnerable mammals in Australasia today, with multiple species having gone extinct within the last 100 years. By demonstrating their profound evolutionary antiquity, we can thus serve to highlight how extremely urgent it is to protect these living fossils as part of Australia’s unique biodiversity”, Dr. Kear is quoted as saying in the Heritage Daily article.
The study has been published in Scientific Reports.
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