Paleontologists from the University of New South Wales have unearthed the fossilized remains of three new species in the thylacinid genera Badjcinus, Nimbacinus, and Ngamalacinus in the Upper Oligocene deposits of the Riversleigh World Heritage Area, northwestern Queensland, Australia. Named Badjcinus timfaulkneri, Nimbacinus peterbridgei, and Ngamalacinus nigelmarveni, these new species are among the oldest thylacinids yet known and indicate an earlier diversification of the thylacine family Thylacinidae than previously understood.
Badjcinus timfaulkneri feeding on the carcass of Silvabestius michaelbirti. Image credit: Peter Schouten.
The three new species of thylacinids lived during the Late Oligocene epoch 25 to 23 million years ago.
The largest of them, Badjcinus timfaulkneri, weighed between 7 and 11 kg — about the same size as a large Tasmanian devil.
“Like Tasmanian devils, the jaw bone of Badjcinus timfaulkneri could easily crunch through the bones and teeth of its prey,” said lead author Tim Churchill, a Ph.D. student at the University of New South Wales.
“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.”
The second species, Nimbacinus peterbridgei, was slightly larger than a tiger quoll, weighing around 3.7 kg.
This species was described from a near-complete jaw bone from White Hunter Site at Riversleigh.
“Nimbacinus peterbridgei was a more generalized predator that probably focused on small mammals and other prey species that lived in Riversleigh’s ancient forests,” said University of New South Wales 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 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, Ngamalacinus nigelmarveni, weighed around 5.1 kg and was about the size of a red fox. It also came from White Hunter Site at Riversleigh.
“This was a highly carnivorous thylacine,” said Dr. Sue Hand, also from the University of New South Wales.
“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.”
According to the team, the presence of three distinct lineages of specialized thylacinids during the Late Oligocene highlights how quickly this group of marsupials diversified after first appearing in the fossil record.
“These new species exhibit very different dental adaptations, suggesting there were several unique carnivorous forest niches available during this period,” Churchill said.
“All but one of these lineages — the one that led to the modern thylacine — became extinct by 8 million years ago.”
“The once suggested idea that Australia was dominated by reptilian carnivores during this 25-million-year long interval is steadily being dismantled as the fossil record of marsupial carnivores, such as these new thylacinids, increases with each new discovery,” Professor Archer said.
“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,” Churchill added.
The study was published this month in the Journal of Vertebrate Paleontology.
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Timothy J. Churchill et al. Three new thylacinids (Marsupialia, Thylacinidae) from Late Oligocene deposits of the Riversleigh World Heritage Area, northwestern Queensland. Journal of Vertebrate Paleontology, published online September 6, 2024; doi: 10.1080/02724634.2024.2384595
Source : Breaking Science News