Australian scientists have discovered a new extinct species of marsupial lion that roamed the remote reaches Queensland around 19 million years ago.
This new species, called Wakaleo schouteni after Australian wildlife illustrator and palaeo-artist Peter Schouten, is estimated to have weighed around 23 kilograms and would have been around the size of a dog.
Palaeontologists from the University of New South Wales have based their findings, published in the Journal of Systematic Palaeontology, on the fossilised remains of W. schouteni’s skull, teeth, and humerus, or upper arm bone, that were found in the Riversleigh World Heritage Area of remote north-western Queensland.
Riversleigh, located about 250 kilometres north-west of Mount Isa in Queensland, is one of Australia’s most important fossil sites as it contains remains from 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.
Lead author Dr Anna Gillespie says the new species is similar in size to a Border Collie and would have been perfectly adapted to the what is thought to have once been a heavily forested region.
“It is quite possible that this animal was able to climb trees and pursue its prey through the tree-tops, like a leopard,” Dr Gillespie told The New Daily.
W. schouteni’s is about a fifth of the weight of the largest and last surviving marsupial lion, Thylacoleo carnifex, which weighed around 130 kilograms and has been extinct for around 30,000 years.
Members of the Thylacoleonidae family of extinct marsupials ranged from the size of kitten to a leopard and had distinct large, blade-like, flesh-cutting premolar teeth.
“This species differs from other species of Wakaleo in having more upper premolars [three] and more molars [four],” said Dr Gillespie.
“This is significant because species of Wakaleo were initially distinguished by their reduced premolar number [two or less].”
She explained that W. schouteni’s teeth suggest that it most like a meat-eater, or carnivore, but could also have been an omnivore with diet of plant and meat.
The bladed premolar teeth “indicates the requirement for cutting and slicing”, whereas the wrinkled surface observed on the molars “suggests the need for smaller transverse movements to cut up material”.
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.
Fossils found in Riversleigh are often very well-preserved – ancient plants and animals that were covered by the soft freshwater limestone were not compressed by it, which meant their three-dimensional structure was retained.
The UNSW team’s discovery of W. schouteni comes just a year after they had unearthed the fossilised remains of a smaller, kitten-sized marsupial lion, also in Riversleigh, which they named Microleo attenboroughi after Sir David Attenborough.
It sheds new light on the evolutionary relationships between two different marsupial lion species from the late Oligocene period – W. schouteni and the slightly smaller and newly-renamed Wakaleo pitikantensis.
The similarities between the new species and Priscileo pitikantensis, specifically the presence of three upper premolars and four molars, prompted the researchers to reclassify P. pitikantensis as a Wakaleo.
“The identification of these new species have brought to light a level of marsupial lion diversity that was quite unexpected and suggest even deeper origins for the family,” Dr Gillespie said.