Evrim Yazgin
Cosmos science journalist
New members have been added to the family tree of the now extinct thylacine, also known as the Tasmanian tiger (Thylacinus cynocephalus).
Fossils of the new species were found in northwestern Queensland Riversleigh World Heritage Site. The site is more than 2,500 km from the southern island of Tasmania where the last Tasmanian tigers lived after it separated from mainland Australia 12,000–14,000 years ago.
Thylacines died out on mainland Australia and New Guinea 3,600–3,200 years ago.
After European settlement, the remaining thylacines in Tasmania were hunted to extinction. The last individual, named Benjamin, died in Hobart’s Beaumaris Zoo in 1936 – just 2 months after the species was given protected status.
The newly discovered ancient thylacines are described in a paper published in the Journal of Vertebrate Palaeontology.
All the new species lived 23–25 million years ago during the Late Oligocene.
During this time, most of the continent was covered in forest with today’s “red centre” home to vast freshwater lakes home to flamingos and freshwater dolphins.
The largest of the thylacine ancestors – Badjcinus timfaulkner – detailed in the new study was 7–11 kg. This makes it much smaller than the modern thylacine which reached about 30kg. It would have been about the size of a large Tasmanian devil.
“Like Tasmanian devils, the jawbone of Badjcinus timfaulkneri could easily crunch through the bones and teeth of its prey,” says lead author Tim Churchill, a PhD student from the University of New South Wales (UNSW).
“But up until now, the much smaller Badjcinus turnbulli, which weighed around 2.7 kg, was the only other late Oligocene thylacinid known,” he adds. B. timfaulkneri is older, making it the oldest undoubted thylacine discovered.
Nimbacinus peterbridgei, the second newly discovered thylacine, was only about 3.7 kg.
“Nimbacinus peterbridgei was a more generalised predator that probably focused on small mammals and other prey species that lived in Riversleigh’s ancient forests,” says co-author Mike Archer, a professor at UNSW.
“We think it may have been on the direct line to the only other species of Nimbacinus, the larger Nimbacinus dicksoni (5 to 7 kg) that was found in 15-million-year-old deposits at Riversleigh.
“This group of thylacines appears to be the one that led directly to the species of Thylacinus. The other two new species being described here appear to represent distinctive side branches on the Thylacine’s increasingly complex family tree. This means Nimbacinus peterbridgei is probably the oldest direct ancestor of the Tasmanian tiger yet known.”
The third new species is Ngamalacinus nigelmarveni. It would have been about 5.1 kg – roughly the size of a red fox.
“This was a highly carnivorous Thylacine,” says co-author Sue Hand, also a professor at UNSW.
“We know this because the cutting blades on its lower molars are elongated with deep V-shaped, carnassial – or ‘meat-cutting’ – notches. Ngamalacinus nigelmarveni had these notches better-developed than any of the other thylacinids of similar size.”
Churchill explains that the different teeth of the ancient thylacines show how quickly they diversified to fill different ecological carnivore niches.
“All but one of these lineages – the one that led to the modern thylacine – became extinct by 8 million years ago.
“The diversity of mammalian carnivores at Riversleigh during this period rivals that seen in any other ecosystem, including the great mammalian carnivore radiation that developed in South America.”
