Only a single specimen of Microleo has been found, dating from 19 million years ago in the Riversleigh World Heritage Area in north-west Queensland. The single fossil is far from complete, so no one knows if it possessed the vicious claw that contributed to Thylacoleo’s capacity to tackle Australia’s ancient three-ton wombats.
“We’ve got the important bit, though,” Gillespie told IFLScience. “We have the third premolar, the huge cutting tooth that is a feature of all marsupial lions.” This tooth, shaped like a blade, was used by the family to slice into any prey unfortunate enough to be hunted by a member of the family.
The range of carnivores in Riversleigh reflected the extraordinary richness of prey species, Gillespie added. “The diversity at the time was comparable to what we now see in Borneo, so there were lots of niches for predators.” As the continent dried out the smaller marsupial lions were replaced with Dasyurids, such as quolls and antechinuses.
An artist's impression of Nevil's Garden, the dig site at Riversleigh where Microleo was found, including the larger marsupial lion Wakaleo. Dorothy Dunphy
David Attenborough has already been honored with the names of at least ten other species, most famously a long-beaked echidna that may or may not be extinct. Gillespie told IFLScience the reason to name another species after the documentary presenter is his role in promoting the Riversleigh deposits.
“He has called Riversleigh one of the four most significant fossil sites in the world. At most places we just get a snapshot in time, but Riversleigh spans 26 million years, allowing us to document the changing fauna in one place, and David has been instrumental in publicizing that,” she said.