Worm Lizards Spread Across the World by 'Rafting' Over the Oceans

Tiny, burrowing reptiles known as worm lizards may have dispersed by rafting across the oceans soon after the extinction of dinosaurs rather than by continental drift. Scientists have used information from fossils and DNA from living species to create a molecular clock to give a more accurate timescale of when the different species split apart from each other.

In this latest study, the researchers studied fossils of worm lizards. Worm lizards are a type of burrowing lizard that lives almost exclusively underground. The six families of worm lizards are found in five different continents. How exactly these animals spread out so widely, though, has long puzzled scientists.

With this latest research, though, the scientists discovered that worm lizards evolved rapidly and expanded to occupy new habitats around 65 million years ago, just after the impact of an asteroid that caused the mass extinction of around 75 percent of living things on Earth, including the dinosaurs. Because this particular event occurred after the break-up of the super-continent Pangaea, the researchers conclude that these animals could not have dispersed across the globe using land bridges.

"Continental drift clearly can't explain the patterns we're seeing," said Nick Longrich, one of the researchers, in a news release. "Continental breakup was about 95 million years ago, and these animals only become widespread 30 million years later. It seems highly improbably not only that enough of these creatures could have survived a flood clinging to the roots of a fallen tree and then travelled hundreds of miles across an ocean, but they were able to thrive and flourish in their new continent. But having looked at the data, it is the only explanation for the remarkable diversity and spread of not just worm lizards, but nearly every other living thing as well."

It's likely that mass extinction actually helped the survivors of the asteroid hit colonize new places and diversify because there was less competition for food from other species. Worm lizards likely survived and thrived, travelling across the oceans at least three times.

The findings are published in the journal Proceedings of the Royal Society B.

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