Primitive Dog-sized Marsupial Lion Discovered in Queensland

Wakaleo was about the size of a basset hound and thrived at top of Australian food chain, but it couldn't adapt to climate change 16 million years ago

Paleoartist's impression of a Wakaleo schouteni marsupial lion challenging a thylacine over the carcass of a kangaroo in the early Miocene forests of Riversleigh
Paleoartist's impression of a Wakaleo schouteni marsupial lion, right, challenging a thylacine, left, over the carcass of a kangaroo, supine, in the early Miocene forests of Riversleigh Peter Schouten

Scientists in Australia have discovered a primitive species of marsupial lion that prowled Queensland around 24 million years ago. Though diminutive relative to later marsupial lions and apparently an omnivore to boot, the extinct "lion" was armed with formidable fangs and was probably among the alpha predators in the late Oligocene food chain.

Going by the scientists' reproduction, Wakaleo schouteni frankly looks other than majestically leonine, though it does seem to have a cattish nose. It seems to have had a muscled tail not unlike a kangaroo's.

The exciting discovery was reported on Thursday in the Journal of Systematic Palaeontology, by Anna Gillespie, Michael Archer and Suzanne Hand of the University of New South Wales.

This previously unknown species of marsupial lion was about the size of a basset hound, averaging about 22.6 to 24 kilograms in weight, estimate Gillespie and the team based on the extinct animal's skull length, which is the usual predictor of body mass in fossil mammals, including marsupials.

For comparison, the male African lion weighs eight times as much: 190 kilos, on average, the female about 130 kilos.

Skull of the marsupial lion species newly discovered  in Queensland: Wakaleo schouteni
Anna Gillespie

To be clear, the marsupial lion was not a member of, or precursor of, the felidae. Cats are placental mammals and this was a marsupial. No connection. The name "lion" stems mainly from the size of the biggest specimens and the animal's status in the prehistoric pecking order.

Based on the range of sizes among the skeletons they found, the paleontologists suspect Wakaleo schouteni exhibited sexual dimorphism, meaning the males were bigger than the females.

The primitive cousin

Wakaleo schouteni 's dentition seems primitive compared with later marsupial lion species. Its set of teeth also led the paleontologists to surmise that the fearsome predator was in fact omnivorous.

"In comparison to other mammalian dentitions, its cutting premolar was long relative to the length of the molar row, hence this points to an emphasis on the biting/slicing function," Gillespie explains.

Similarly, based on the presence of an extra grinding molar compared with later species of marsupial lion, the scientists speculate that Wakaleo was omnivorous. Later marsupial lions living some 10 million years ago are believed to have become hypercarnivores: existing mostly on meat.

Miniature lions the size of rats

The marsupial lion family contained 10 species, including our Wakaleo schouteni. The marsupial lions were probably peak mammalian carnivores in late Cenozoic Australia. Their main competition was apparently crocodiles, Gillespie told Haaretz.

Over time, as the "lions" evolved and morphed from eating whatever to eating meat, they also tended to increase in size, a typical attribute of carnivores. The smallest was understandably called "Microleo".

"We have estimated that Microleo attenboroughi weighed around 600 grams," which is just over a pound, Gillespie says. That's about the size of a very small rabbit or hefty rat.

The biggest marsupial lion species, Thylacoleo carnifex, has been estimated to have weighed up to around 130 kilograms and may have been as much as 1.5 meters long, she adds. Ergo, this was rather more lionlike.

North American Opossum with winter coat.
Wikipedia

All other things being equal, omnivores would generally be smaller than carnivores. The paleontologists speculate that marsupial lions grew over time in size partly because of changes in the availability of animals to eat.

"The increase in body size of Wakaleo is most likely linked to increases in body size of their prey such as the larger herbivores that co-existed during the Miocene. In turn, the latter were responding to changes in the vegetation that occurred as the continent became drier and cooler, at least during the latter part of the middle Miocene and into the late Miocene," Gillespie says.

Marsupial lion lineages are a complicated thing. Three species are known to have existed from the late Oligocene period, two of which were species of Wakaleo, Gillespie explains. "It is likely that the species of Wakaleo found in the later time period, the Miocene, evolved from one of these early Wakaleo species, possibly Wakaleo schouteni."

Microleo and others apparently  arose from an earlier, but different marsupial lion branch, she adds.

So, did the marsupial lions meet and eat the aborigines, or vice versa? Though it is evocative to imagine a great hulking marsupial monster lurking in a tree and dropping down on prehistoric humans, there's no evidence of a meeting between the species, says Gillespie, although there may have been some parallels in time frame regarding the earliest humans in Australia and the latest marsupial "cats".

Sadly, Wakaleo went extinct during the Pleistocene, about 16 million years ago, together with most of Australia's mega-fauna. "This is believed to have been caused by climate change - Australia becoming much drier," Gillespie says. In contrast to the theropods that evolved into birds, the marsupial lions evolved into nothing.

Today's living marsupials, from the kangaroo to the ubiquitous opussum, arose from ancestors that co-existed with the marsupial lions. They however did manage to adapt to the change in climate. The lion, evidently, did not.