Tasmania tiger relative more like a quoll

By Signe Cane 11 April 2014
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Tasmanian tiger’s ancient relative had more powerful jaws than its size would suggest

UNLIKE THE TASMANIAN tiger, whose relatively weak jaw strength meant it was better suited to hunting small animals, an ancient relative was capable of taking down prey larger than itself.

Australian researchers have discovered that, Dickson’s thylacine (Nimbacinus dicksoni), an ancient cousin of the Tasmanian tiger, had a powerful bite capable of subduing much larger prey than its own body weight.

“The biomechanical performance of Nimbacinus is more similar to that of dasyurids – such as quolls – than of thylacinids. That would suggest it hunted a large variety of prey,” says zoologist Marie Attard from the University of New England in Armidale.

“In contrast, the iconic Tasmanian tiger was considerably more specialised than large living dasyurids and Nimbacinus, and was likely more restricted in the range of prey it could hunt, making it more vulnerable to extinction,” says Marie.

Nimbacinus jaw bite compared to Tasmanian tiger

In order to determine the killing prowess of Nimbacinus, the researchers created a virtual 3D reconstruction of its skull and jaw, using an approximately 16 million-year-old fossil finding from Riversleigh in north-western Queensland.

The reconstruction was converted into an engineering model that allowed the scientists to predict the performance of the skull in different biting and killing conditions. The results were then compared to models of the Tasmanian tiger, a range of native quolls and the Tassie devil.

“The way to get reliable evidence is to compare the biomechanics of an extinct species to those of currently living ones,” says Marie.

Surprisingly, the researchers discovered that unlike the Tassie tiger, its cousin Nimbacinus had a bite force that’s closest to the spotted-tailed quoll (Dasyurus maculatus). The Tasmanian tiger was once blamed for killing sheep on farms, but research has shown its jaw and elbow joints were better suited to hunting prey smaller than itslef.

The spotted-tailed quoll is mainland Australia’s largest carnivorous marsupial, with the largest males reaching the size of 5 kilograms. Deceptively cute, the spotted-tailed quoll is an apex predator, capable of taking down considerably larger prey than itself.

Nimbacinus more like a quoll than a thylacine

About as big as a large domestic cat, Nimbacinus was an average predator for its time, says Marie. “There aren’t a lot of fossils around from other thylacinids, which makes it difficult to draw conclusions about the family.”

Nimbacinus most likely hunted birds, reptiles and a range of marsupials, including possums and small wallabies. The researchers believe that the similarities between Nimbacinus and the spotted-tailed quoll are a result of convergent evolution, when two species evolve similar features independently because of the similarities in their environment.

“I’m interested in thylacinids from the perspective of the Tassie tiger. By looking at related carnivores, we can determine how specialised their hunting abilities were,” Marie told Australian Geographic.

The study was published this week in PLOS ONE.