The latest creature found at world-heritage listed Riversleigh Fossil Field is a small marsupial lion that lived 23 million years ago.

University of New South Wales researchers have classified a new species of marsupial carnivore, named 'Lekaneleo' which hunted rainforests that were in the Riversleigh area at the time.

They made the discovery while studying bone fragments dug up decades ago and were originally believed to belong to another species.

Professor Michael Archer of the University of NSW Biological, Earth and Environmental Sciences.said they discovered unique physical attributes in these fragments that showed it was new marsupial lion.

"(It was) the lack of big boney crests around the skull, which is a lack of powerful jaw muscles, that was a distinction from the other marsupial lions," Professor Archer said.

Professor Archer said it was a powerful and opportunistic hunter who hunted birds, mammals and reptiles.

"We suspect with the kind of teeth it had it could eat anything, even things much bigger than itself because those teeth were specially designed to cut meat into pieces. They are like bolt cutters," he said.

Lekaneleo has been nicknamed 'Leo' and was roughly the size of a cat and is thought to be most closely related to wombats.

Prof Archer said they were looking for a more complete skeleton of the animal.

"When much more is known then it may be apparent that the whole thing needs to be reconsidered again," he said.

In 2016 the Riversleigh Fossil Field uncovered two ancestors of kangaroos while in 2017 another marsupial lion was found.

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