Using 3D Technologies to Examine Rare Specimens of the Extinct Tasmanian Tiger

In 1936, the last known Tasmanian Tiger died in captivity at Hobart Zoo; locked out of its shelter, it was unable to survive the extreme daytime heat and below-freezing nighttime temperatures of Tasmania to which it was subjected. Since that time, much like Elvis, there have been sightings of the animal in the wild, but none confirmed, and an exhaustive survey conducted between 1967 and 1973 was unable to confirm the existence of a single one of these singular creatures. Their extinction was brought about by a combination of overhunting – a bounty was placed on the animals by the Van Diemen’s Land Company and sentiment against the animal was whipped up with doctored images showing it stealing poultry – the invasion of its territory by humans, competition with wild dingoes, and the introduction of domestic dogs.

The Tasmanian Tiger was actually not related to its feline namesake, but was given the name because of the stripes that ran across the lower half of its back. And while very closely resembling a dog, the last time the two animals shared an ancestor was approximately 160 million years ago. Its scientific name is Thylacinus cynocephalus and it is commonly referred to as the thylacine. Joining the ranks of some of Oceania’s most famous creatures, the thylacine was a marsupial, meaning that it carried its young, known as joeys, in a pouch. In fact, both the male and female had pouches, but the male’s pouch was designed to protect his genitalia as he moved through spiky brush. In addition, the animal had a stiff tail, like a kangaroo, and an impressive maw, which it could open wider than its own head.

Museums have a small collection of specimens of this now extinct animal, and because they are marsupials, a small number of those examples have had joeys in their pouches. The number of these joeys though is extremely limited, with only 13 known to exist in collections around the world. Over the years there have been numerous requests to dissect and otherwise study the the little beasts, but all requests have been declined due the damaging nature of such invasive study techniques. However, with the development of non-invasive X-ray micro-CT scanning, it is now possible to take a look inside the babies without doing them the least amount of harm.

The benefits were immediately obvious, as explained by Senior Curator of Vertebrate Zoology, at the Tasmanian Museums and Art Gallery (TMAG) Kathryn Medlock:

“By examining their bone development, we’ve been able to illustrate how the Tasmanian tiger matured, and identify when they took on the appearance of a dog. One of the major advantages of this new technology is that it has enabled us to do research and answer many questions without destruction of the sample specimens.”

One of the first discoveries that was made when researchers from Museums Victoria and the University of Melbourne began to examine the known specimens was that two of them, from the collections of the TMAG, very likely weren’t thylacine at all, but rather some other form of marsupial baby with a similar early development trajectory. The data gathered from this scanning project has been released in a paper and covers the five critical stages of pouch development for the extinct joeys.

The contents of the paper provide important information about this animal’s development that was not previously available, as described by lead author and University of Melbourne PhD student Axel Newton:

A scan reveals the internal structure of Tasmanian Tiger joeys. [Image: University of Melbourne]

“Our 3D models have revealed important new information about how this unique extinct marsupial evolved to look so similar to dogs, such as the dingo, despite being very distantly related. The digital scans show that when first born the Tasmanian tiger looked like other marsupials like the Tasmanian Devil or the kangaroo. These scans show in incredible detail how the Tasmanian tiger started its journey in life as a joey boasting the robust forearms of other marsupials so that it could climb into its mother’s pouch. But by the time it left the pouch around 12 week to start independent life, it looked more like a puppy with longer hind limbs than forelimbs.”

The digital files for the 3D scans have been made available freely for anyone who wishes to use the data as part of their research or who has simply had their curiosity piqued. 3D technologies are helping scientists to better understand extinct species, as 3D scanning can exactly reproduce anatomies into 3D models that can then be 3D printed to allow for handling and a closer look without damaging delicate bones or fossils.

Unfortunately, the great care being taken now not to damage an animal whose end so clearly came as a result of not just carelessness, but active malice, is too little, too late for the animal, however, there is some hope that we can at least learn something from our recklessness.

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[Sources: University of Melbourne, BBC]