In North America, skinks are often tiny, slick and snakelike — with shiny blue tails or bright red heads. Nearly all of them can fit in the palm of your hand. But more than 47,000 years ago, an armored tank of a skink walked the desert lands of Australia.
“It was nicknamed ‘megachunk’ or ‘chunksaurus,’” due to the thickness of its bones, says Kailah Thorn, a paleontologist at the Western Australia Museum who recently described the species for the first time. “It’s a pretty heavy metal lizard.”
Thorn and her colleagues only just identified the species Tiliqua frangens this June, in a study published in Proceedings of the Royal Society B: Biological Sciences. But the bones of the creatures themselves were discovered long before — then subsequently forgotten.
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Recent Rediscovery
The Wellington Caves in New South Wales is one of Australia’s most storied systems for fossils. Cathedral Cave, part of this system, is where researchers first unearthed Australian megafauna fossils from the largest known marsupials to ever live, the marsupial lion and Diprotodon optatum.
Researchers have also unearthed giant kangaroo fossils in the area, as well as those from the Megalania (the larger extinct cousin of the Komodo dragon) and Australia’s giant eagle, Dynatoaetus gaffae.
Among these more famous discoveries, researchers also found other armored bones; they appeared to come from a skink species, but were often thrown into “miscellaneous bone boxes” in the rush and more or less forgotten over time.
When Thorn and her colleagues later began rediscovering pieces from the Western Australian Museum and other repositories, the consensus was still that these bones — because of their range of sizes — likely belonged to two species of armored skinks.
But when Thorn’s team began matching bones together, it found that the fossils were likely from just one species. The smaller ones likely belong to skinks that were relatively young at the time of their deaths. Others had the kind of overgrown bones you often see in older individuals — or, in one case, “a big, old, gnarly-toothed guy,” Thorn says.
Giant Skinks
Once Thorn and her colleagues gathered enough bones, they found that many fit together quite nicely.
In the end, the team had a heavily armored skink that, as an adult, might be as long as a human arm — exceptionally large — plus a tail, though the fossil evidence hasn’t yet revealed if the T. frangens has a short, knobby tail or a longer tail like most skinks. Many of its armored plates are also equipped with dull spikes.
Its nearest living relative is the shingleback skink, a large individual itself in the skink world. These skinks are unique in appearance, with relatively armored scales and a rounded tail that appears similar to its head.
“It really broadens our ideas of skink body shapes — the sizes they were able to reach and their lifestyle,” Thorn says.
Shinglebacks are also unique in the fact that, unlike most reptiles, they give live birth to a baby lizard so large it would be proportionately equal to a human giving birth to a 3-year-old child. T. frangens was likely no different; indeed, the entire group of skinks gives live birth, though the smallest baby fossils found weren’t proportionately so large.
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What Did Ancient Skinks Eat?
Thorn says that these ancient skinks probably ate tough plant matter, similar to shinglebacks and desert tortoises. They would have fit a similar niche to the latter, as a slow-moving desert herbivore. The fossil evidence hasn’t yet revealed what ate them in turn, but Thorn says their spines would likely have dissuaded many predators.
“This animal is just out and proud and not really worrying about it,” she says.
It’s possible that extremely large Tasmanian devils, which were still present on the Australian mainland around this time, might have gone for them. Giant eagles are another possible predator. Today, Thorn says, birds of prey will sometimes flip shinglebacks over and peel off the relatively softer scales from their bellies to get at flesh.
“The marsupial lion might have had a stab at it,” she adds. Any one of these predators might have long ago dragged the skinks into the Wellington Caves, where the fossils were found.
Skink Extinction
The oldest fossils of T. frangens date to about 1 million years ago, in a part of the Wellington system called the Big Sink. The most recent fossils yet found date to around 47,000 years ago in the same system — a date that matches pretty well with the supposed extinction dates of many of Australia’s largest animals.
Species like the marsupial lion, the giant eagle and the Megalania also blinked out of the fossil record around this time. Paleontologists still debate exactly why this happened, as around that time two major things happened in Australia: The climate changed a lot and humans arrived for the first time on the continent.
For Thorn, both factors probably played are role in this mass extinction. “[The skink]’s gone extinct at the same time as the rest of Australia’s megafauna,” she says. “It affected the whole ecosystem, not just the really big herbivore/carnivore mammals.”
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