SYDNEY, June 15 (Xinhua) -- Researchers have identified a previously unknown branch of the marsupial family tree, a finding that could reshape understanding of how Australia's unique mammals evolved.
In a study published in the Journal of Paleontology, scientists from Australia's University of New South Wales (UNSW) described three new species of small, insect-eating marsupials discovered at the Riversleigh World Heritage Area in the state of Queensland, according to a UNSW statement released on Monday.
The fossils, mainly teeth and jaw fragments, are distinct enough for the team to propose a new marsupial order, named Keeunamorphia, it said.
The animals, estimated to have weighed 25-200 grams, lived about 18 million years ago in northern Australia's rainforests, though their evolutionary roots may date back more than 50 million years, shortly after marsupials arrived in the continent from South America via Antarctica, researchers said.
"Not only is it a new order, but it could also be one of the most ancient lineages of Australian marsupials," said UNSW paleontologist Timothy Churchill, the study's lead author.
The team found the species "were not closely related to any other marsupials living alongside them." Instead, their teeth resembled those of much older species, indicating a long-surviving, separate evolutionary line.
"Evolutionary history is a lot more complex than just one group leading to all of Australia's marsupials," with multiple ancient lineages potentially coexisting, Churchill said, adding significant gaps in the fossil record mean the earliest chapters of marsupial evolution are still being written. ■
