Worm Lizards Floated Their Way Around the World

Two Iberian worm lizards (Blanus cinereus) in a garden near Seville, Spain. Richard Avery via Wikimedia Commons CC3.0

Around 65 million years ago a large meteorite slammed into the Earth. This catastrophic event likely wiped out the dinosaurs, and a majority of species on Earth. But there was one little-known beneficiary of the asteroid impact: the worm lizard.

These creatures, which are occasionally mistaken for earthworms and are generally less than six inches long, live mostly in the soil and are found in parts of the Americas, Europe and Africa.

Scientists looking into the creatures' evolutionary past found that these animals originated in North America and then, just after the mass extinction, spread to Europe. From there they also made their way to Africa, and then from Africa to South America.

This is a big finding in the tiny world of worm lizard biology. It had once been assumed that they dispersed on the supercontinent Pangea before it broke up and the various continents spread apart. Instead, this new genetic analysis suggests these little creatures actually floated between continents at least three different times, according to the study, published in the Proceedings of the Royal Society B.

Animals like (legged, non-worm) lizards and insects have been shown to do this, by clinging to pieces of wood or other debris, and "rafting" between land masses. But it was considered "highly improbable not only that enough of these creatures could have survived a flood clinging to the roots of a fallen tree and then traveled hundreds of miles across an ocean, but that they were able to thrive and flourish in their new continent," says study co-author Nick Longrich, from the University of Bath, in a statement.

"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," Longrich adds. "Once you eliminate the impossible, whatever you're left with, no matter how improbable, must be the truth."

After the meteorite impact, there were few plants, due to blockage of sun from suspended aerosols in the atmosphere. The researchers speculate that these legless burrowing beasts, in a taxonomic group called Amphisbaenia, in the were able to thrive while others died since they feast on dead and decaying matter.

Tunnels dug by the animals "would have acted like bomb shelters, allowing them to withstand the asteroid impact and without any competition for food and space, they flourished," says University of Bristol researcher Jakob Vinther.