Like kangaroos and koalas, this fearsome creature was a marsupial but unlike today's descendent it was a meat-eater, armed with a fearsome set of teeth.
The new species is about a fifth of the weight of the largest and last surviving marsupial lion, Thylacoleo carnifex, that weighed in at around 130 kilograms and which has been extinct for 30,000 years.
A team of Australian scientists has discovered a new species of marsupial lion which has been extinct for at least 19 million years.
The University of New South Wales scientists who made the discovery named the lion Wakaleo schouteni in honour of paleoartist Peter Schouten. Members of this family, the Thylacoleonidae, had highly distinct large, blade-like, flesh-cutting premolars that they used to tear up prey.
A new species of extinct lion that inhabited lush rainforest more than 18 million years ago has been discovered in the Australian outback.
The meat-eating marsupial is estimated to have been about the size of a dog and weighed around 23 kilogrammes, the researchers said.
With this new find, the researchers believe that two different species of marsupial lion were present in the late Oligocene at least 25 million years ago.
The discovery comes just a year after the fossilised remains of a kitten-sized marsupial lion were found in the same fossil site in Queensland.
The Riversleigh World Heritage Area where the species was found, located about 250 kilometres north-west of Mt Isa in Queensland, contains the remains of ancient mammals, birds and reptiles from the Oligocene (33.9 to 23 million years ago) and Miocene (23 to 5.3 million years ago) epochs.
It was found at the internationally-renowned Riversleigh World Heritage Area in the remote north-western Queensland state, where the remains of a bevvy of unusual new small to medium-sized creatures have been discovered.
The Wakaleo schouteni didn't have almost the same toothy "smile", based on fossilized remains of its skull, teeth and an upper arm bone.
The new findings of the small, dog-sized marsupial (Wakaleo schouteni) shows many similarities to other marsupials of the genus Wakaleo.
"The identification of this species has brought to light a level of marsupial diversity that was quite unexpected, and suggest even deeper origins for the family", lead study author Anna Gillespie said in a statement.
By examining the teeth of the newly identified specimen, Dr Gillespie and her collaborators have deduced that it is one of the most primitive marsupial lions discovered so far.