Saber-Toothed Metatherian — Thylacosmilus Atrox — Killed With A Unique Combination Of Extreme Precision And Strength, Research Finds

Thylacosmilus atrox — a species of saber-toothed metatherian that lived in South America millions of years ago — must have killed with extreme precision due to several anatomical peculiarities, new research from the University of New South Wales has found. In addition to have relatively fragile teeth which could break easy — as most saber-toothed animals did — Thylacosmilus atrox also, interestingly, had a bite that was weaker than that of a domesticated cat, according to the new research.

Image Credit: Thylacosmilus via Wikimedia Commons
Image Credit: Thylacosmilus via Wikimedia Commons

Certainly interesting for an animal that averaged about 350 lbs. The species apparently relied on its extremely powerful forearms and neck muscles in order to first wrestle down its prey and then to deliver an extremely precise kill bite with their saber-teeth — directly into the arteries of the neck or the windpipe.

The species was already known to be quite a bit if fervent in appearance than any animals alive today — but now the new research has shown that they likely behaved quite a bit differently as well. “Thylacosmilus looked and behaved like nothing alive today,” states UNSW palaeontologist, Dr Stephen Wroe, head of the research team.

“To achieve a kill the animal must have secured and immobilized large prey using its extremely powerful forearms, before inserting the sabre-teeth into the windpipe or major arteries of the neck — a mix of brute force and delicate precision.”

When you think of a saber-toothed animal the first thing that comes to mind is likely ihe iconic North American sabre-toothed cat — Smilodon fatalis — but there was actually quite a large diversity of saber-toothed animals alive in the past. As far as is currently known, saber-teeth evolved separately five different times in mammals during the last 65 million years — And Thylacosmilus atrox is actually the best represented of these species in the fossil record.

The University of South Wales provides details on the species and the new research:

For its size, its huge canine teeth were larger than those of any other known sabre-tooth.
Smilodon’s killing behaviour has long attracted controversy, but scientists now mostly agree that powerful neck muscles, as well as jaw muscles, played an important role in driving the sabre-teeth into the necks of large prey. Little was known about the predatory behaviour in the pouched Thylacosmilus.

To shed light on this super-predator mystery, Dr Wroe’s team of Australian and US scientists constructed and compared sophisticated computer models of Smilodon and Thylacosmilus, as well as a living conical-toothed cat, the leopard. These models were digitally ‘crash-tested’ in simulations of biting and killing behaviour.

"This shows cut away views through the skulls of (A) the sabre-toothed 'tiger' (Smilodon) and (B) the bizarre pouched sabre-tooth (Thylacosmilus). Note the incredibly wide gape and huge canine teeth with roots extending almost into the braincase of Thylacosmilus." Image Credit: S. Wroe
“This shows cut away views through the skulls of (A) the sabre-toothed ‘tiger’ (Smilodon) and (B) the bizarre pouched sabre-tooth (Thylacosmilus). Note the incredibly wide gape and huge canine teeth with roots extending almost into the braincase of Thylacosmilus.”
Image Credit: S. Wroe

“We found that both sabre-tooth species were similar in possessing weak jaw-muscle-driven bites compared to the leopard, but the mechanical performance of the sabre-tooths skulls showed that they were both well-adapted to resist forces generated by very powerful neck muscles,” states Dr Wroe. “But compared to the placental Smilodon, Thylacosmilus was even more extreme.”

“With its jaws wide open this 80-100 kg ‘super-predator’ had a bite less powerful than a domestic cat. On the other hand — its skull easily outperformed that of the placental Smilodon in response to strong forces from hypothetical neck muscles. Bottom line is that the huge sabres of Thylacosmilus were driven home by the neck muscles alone and — because the sabre-teeth were actually quite fragile — this must have been achieved with surprising precision.”

“For Thylacosmilus — and other sabre-tooths — it was all about a quick kill. Big prey are dangerous — even to super-predators — and the faster the kill the less likely it is that the predator will get hurt — or for that matter attract unwanted attention from other predators.”

“It may not have been the smartest of mammalian super-predators — but in terms of specialization — Thylacosmilus took the already extreme sabre-tooth lifestyle to a whole new level,” says Dr Wroe.

The new research was just published in the journal PLoS ONE.

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