Scientists have discovered the fossils of three new species of thylacine – or Tasmanian tiger – from the Riversleigh World Heritage Area in Waanyi country of north-western Queensland, Australia.
Palaeontologists say the new species are now the oldest members of the thylacine family to date, estimated to be 25-23 million years old.
The discoveries highlight how quickly this group of marsupials diversified after first appearing in the fossil record, say researchers, who published their findings in the Journal of Vertebrate Paleontology.
Bone crusher
The largest of the new thylacine species discovered is Badjcinus timfaulkneri, which weighed between 7–11 kilograms – about the same size as an adult Tasmanian devil.
“Like Tasmanian devils, the jawbone of Badjcinus timfaulkneri could easily crunch through the bones and teeth of its prey,” says study lead author and PhD student Tim Churchill.
“But up until now, the much smaller Badjcinus turnbulli, which weighed around 2.7 kg, was the only other late Oligocene thylacinid known.
"The teeth – including the lower jaw and isolated first molar – were found at Hiatus Site at Riversleigh, which is even older than White Hunter Site where Badjcinus turnbulli was previously found.
"This makes Badjcinus timfaulkneri the oldest undoubted thylacine discovered so far.”
“Like Tasmanian devils, the jaw bone of Badjcinus timfaulkneri could easily crunch through the bones and teeth of its prey.”
Ancient forest hunter
The second new species discovered was Nimbacinus peterbridgei. A little larger than a tiger quoll, Nimbacinus peterbridgei weighed around 3.7 kilograms and was described from an almost complete jawbone from White Hunter Site at Riversleigh.
“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 Professor Mike Archer.
“We think it may have been on the direct line to the only other species of Nimbacinus, the larger Nimbacinus dicksoni (5 to 7 kilograms) 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.”
Meat butcher
The third new member of the thylacine family is Ngamalacinus nigelmarveni. It weighed around 5.1 kilograms, about the size of a red fox. It also came from White Hunter Site at Riversleigh.
“This was a highly carnivorous thylacine,” says co-author Sue Hand.
“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.”
Three new thylacine species
The three distinct lineages of thylacinids, each with their own specialised adaptations, shows how quickly this group of marsupials diversified, explains Churchill.
“These new species exhibit very different dental adaptations, suggesting there were several unique carnivorous forest niches available during this period,” he says.
“All but one of these lineages – the one that led to the modern thylacine – became extinct eight million years ago. That lineage ended with the death of Benjamin, the last Tasmanian tiger in Hobart’s Beaumaris Zoo on September 7, 1936.”
Read more about the study: Three new thylacinids (Marsupialia, Thylacinidae) from late Oligocene deposits of the Riversleigh World Heritage Area, northwestern Queensland
Main image credit: Badjcinus timfaulkneri feeding on the carcass of Silvabestius michaelbirti. Illustration by Peter Schouten
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