The rare haul of fossils includes 26 skulls from an extinct, sheep-sized marsupial with giant claws.
The finds come from the Riversleigh World Heritage fossil field in north-west Queensland.
The beautifully-preserved remains have been described in the Journal of Vertebrate Paleontology.
“It’s extraordinarily exciting for us,” said University of New South Wales palaeontologist Mike Archer, co-author of the research.
“It’s given us a window into the past of Australia that we simply didn’t even have a pigeonhole into before.
“It’s an extra insight into some of the strangest animals you could possibly imagine.”