Some 90 years after the death of the last documented thylacine — better known as the Tasmanian tiger — the species remains a global symbol of human-made extinction.
The carnivorous marsupial fell victim to 19th-century colonists’ perception that unfamiliar creatures were primitive, vermin-like imitations of more familiar European animals. The species was later exterminated due to sensationalist claims that it was a ferocious, wolf-like predator of sheep.
However, our new study, published in Nature Communications, suggests the thylacine defied the colonialists’ assumptions in every way. It was unique among modern predatory mammals by subduing its prey with high-impact snaps of slender, oversized jaws.
Our focus was on one of the most widely cited cases of evolutionary convergence — the dog-shaped skull of the thylacine, which inspired its species epithet cynocephalus (“dog-head”). This similarity is striking, as thylacines are separated from dogs by more than 120 million years of evolution.
So we set out to understand how deep the similarity really goes.
A massive head with a flimsy face
We used 3D shape analysis to compare scanned thylacine skulls from museums around the world with those of other predatory mammals. This revealed that different regions of the thylacine’s skull resemble those of several other animals.
The thylacine’s long and thin snout looks pretty fragile, most like that of small foxes and jackals. By contrast, the back of the thylacine’s skull resembles that of wolves, dingos and dholes (also known as the Asiatic wild dog).
But the standout feature of this odd patchwork was the thylacine’s enormous head. Its relatively puny 17-kilogram body carried a skull as large as that of wolves, which are more than twice the thylacine’s weight.
So why this skinny jaw on an outsized head?
We suspect this combination let thylacines subdue prey with powerful snapping bites. Thylacine jaws are clearly built for speed: the longer a jaw is, the faster its tip moves during biting.
Combined with the animal’s famously large gape, this should increase the impact of the strike. Long jaws like this are usually quite weak, but the huge size of the thylacine’s skull would have added enough substance to withstand lethal snaps into potentially unsuspecting bandicoots.
The mammalian answer to crocodiles?
But it is the features that are not found in other predatory mammals that may have taken the thylacine’s snaps to a new deadly level.
The thylacine’s upper jaw is exceptionally tall, with a distinctive “pinched” hourglass shape at the tip. This combination is perfect for resisting the stress of high-impact, upwards-directed bites. It also matches earlier results that thylacine canine teeth seem most suited to puncturing, crushing bites (rather than pulling, tearing, or holding).
Thylacines were probably the last modern predatory mammals to sport such a tall, mace-like snout. But similar jaw types are found across other vertebrates, such as crocodiles, and are usually interpreted as adaptations for hunting fast-moving prey.
But some extinct mammals also had thylacine-like snouts, most notably in the gigantic extinct predator Andrewsarchus.
Our results are particularly tantalizing in view of earlier genomic work, which suggested that natural selection acted on regulatory genes in some shared developmental pathways of wolves and thylacines.
It is possible these genomic similarities are behind some of the shared aspects of skull shape between wolves and thylacines. However, as we know, wolves and thylacines did not fill the same ecological niche; we might ask how these genomic convergences produced such a uniquely specialized marsupial predator.
A lesson for urgent and thoughtful future science
Our results highlight — yet again — that the thylacine’s eradication targeted an animal that existed only in the early colonial imagination. But they are also a timely reminder that we cannot afford to repeat this mistake through negligence.
Australia has the worst mammal extinction rate in the world. Its wildlife faces escalating threats from environmental degradation and climate change, as well as new threats such as bird flu.
Museum-based research like ours is needed to illustrate how these statistics reflect irreplaceable biodiversity lost with every extinction.
But we also need to remember Western science is only part of the story — respectfully requesting knowledge from Indigenous custodians about the unique Australian wildlife should be key to our future research.
After all, the people who lived alongside thylacines for tens of thousands of years knew exactly what kind of animal it was.
Vera Weisbecker, Professor in Evolutionary Biology, College of Science and Engineering, Flinders University; Andrew Pask, Professor, School of BioSciences, The University of Melbourne, and Douglass S Rovinsky, Associate Research Scientist, School of Biological Sciences, Monash University
This article is republished from The Conversation under a Creative Commons license. Read the original article.
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