Most skinks look like skinks, by which I mean that most of the 1,500 or so species in the family of lizards we call skinks have the same general body plan. Skinks have no discernible neck and small, stubby legs. Their heads are conical, and their tails are long and tapering. They have smooth, overlapping scales, like those of a fish. In terms of appearance, they are a predictable group of lizards.

But there’s one weird group of skinks in — you guessed it — Australia that’s defied skink convention and evolved some relatively unusual bodies. Now, a group of researchers have published a paper in Current Biology explaining exactly how these strange skinks got so strange. “They have really extreme morphologies, things that I would say are strange,” said Ian Brennan, an evolutionary biologist at the Natural History Museum in London and the Australian National University in Canberra. “But it’s probably not fair to call them strange.”

These skinks are called social skinks because many of them are more social than other lizards. Some species “live in the same crevice with their parents and grandparents and their own offspring, which is pretty unique,” ​​Brennan said. Another species, called the shingleback skink, practices long-term monogamy. “Every spring, the males and females find their mate, the same one they’ve had for five, 10, 20 years,” he said. “They mate, they go together all spring, and then they separate and don’t see each other for the rest of the year.”

Brennan began working with the sociable skinks on another project, collecting genomic data from reptiles and amphibians in Australia—the world’s richest reptile country. He found some of these reptiles so interesting that he wanted to “zoom in on some of them and show some of the really cool evolutionary patterns that we’re seeing,” he said.

The social skinks include the most famous skink in the world, the skink that probably introduced many people to the idea of ​​skinks: the blue-tongued skink. There are many species of blue-tongue skink, all of which have evolved a blue tongue that predators find threatening. The monogamous shingleback skink is one of the blue-tongue skinks and boasts another morphological adaptation that has earned it the nickname “two-headed skink”: the shingleback has evolved a tail so short and bulbous that it almost resembles a second head, an adaptation that can confuse predators trying to guess where the skink will go next.

The social skinks also include a group called crocodile skinks. “They have really spiky scales on their backs,” Brennan said. Then there are the monkey-tailed skinks, which live in trees in the Solomon Islands, where they feed on leaves and fruit. “They’re huge and have long, prehensile tails,” he said. Then there are the crevice skinks, which have short, spiky tails that help the lizards squeeze into rock crevices. “They look pretty gnarled,” Brennan said. Last, but certainly not least, is a group called the slender blue tongues, which are incredibly long, with knobby limbs, small hands and feet, and long tails—like a typical skink has been through a taffy-pulling machine. “So we have some surprisingly large extremes in this group, which lends itself very well to asking questions about how these extreme morphologies evolve,” Brennan said.

Scientists have several theories of evolution, the most famous of which is Darwinian gradualism—the idea that species develop new traits at a relatively steady rate over long periods of time. Another theory of evolution, first articulated by paleontologist George Gaylord Simpson, suggests that new traits can emerge suddenly. If natural selection acts on a trait of an individual or a group of traits, a skink species can go from a small tail to a huge tail quite quickly. “Some people will say things happen gradually,” Brennan said. “And people will say, no, no, change is punctual.” But after analyzing the reconstructed family tree, scientists found that the evolution of social skinks can be explained by both theories of evolution—long periods of slow change punctuated by rapid periods of evolution.

The conditions that led to these evolutionary patterns remain an open question that scientists like Brennan are working to understand. But Brennan does know that social skinks arrived in Australia tens of millions of years ago, at a time when there were no other skink-like animals on the continent. “You come to this continent that doesn’t have anything like you yet, and you can branch out into a lot of different ecological niches,” Brennan said, offering a possible explanation for such rapid change.

Testing the theory, however, is a challenge: “We can’t just build an island, throw animals on it and wait 10 million years,” he said. But if it were possible, who knows what might evolve? Skinks that stink? Skinks that shrink? Skinks that eat and skinks that drink? Skinks that swim and skinks that sink? Just think, think of the unthinkable, sneaky skinks!