Worm lizards are not worms, but they might be the world's most successful stowaways.

Nature · Published 3 October 2026 Swipe more like this →

In short: Amphisbaenians are subterranean reptiles that look like earthworms but possess powerful, interlocking teeth and a unique accordion-like movement. Despite their small size and strictly burrowing lifestyle, these mysterious creatures have managed to colonize continents across the globe, likely by rafting across the Atlantic Ocean on massive mats of vegetation.

Amphisbaenians, or worm lizards, are a group of over 200 species characterized by their elongated bodies, reduced eyes, and often limbless forms. While they superficially resemble earthworms due to their ringed scales, they are true reptiles. Their anatomy is highly specialized for a subterranean life; they move through soil using an accordion-like motion, where trunk muscles shift the body within a tube of skin. Unlike snakes, which have a reduced left lung, amphisbaenians have a reduced right lung to accommodate their narrow frames.

The evolutionary history of these creatures has long been a subject of intense debate. Early theories suggested their global distribution was the result of the breakup of Pangaea, implying they were over 200 million years old. However, modern molecular and fossil evidence indicates they originated in North America around 107 million years ago. Their subsequent spread to Africa, Europe, and South America is now attributed to oceanic rafting during the Paleogene. This hypothesis suggests they survived long voyages on floating debris, a feat made possible by their small size and low nutritional requirements.

Classification remains complex, as convergent evolution has caused many unrelated species to develop similar skull shapes or lose their limbs independently. While traditionally categorized by morphology, researchers now use DNA sequencing to untangle their relationships. Today, six extant families are recognized, ranging from the limbed Bipedidae of Mexico to the diverse Amphisbaenidae found in the tropics. Despite their hidden lives, these animals continue to challenge our understanding of how small, burrowing vertebrates can achieve such remarkable transoceanic dispersal.

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