The Devil’s Corkscrews of Nebraska

In the late 19th century, unusual fossils were discovered in Nebraska. They looked like giant corkscrews twisted straight down into the ground. They were named Daemonelix, meaning “devil’s corkscrews.”

For a long time, scientists did not know what they were. Some thought they might be fossilized roots of huge plants—or even sponges. Then skeletons of small mammals were found inside the spirals, revealing their true origin.

These were burrows dug about 20 million years ago by Palaeocastor, extinct beavers that lived on land.

Unlike their modern relatives, Palaeocastor did not build dams. Instead, they dug spiral tunnels about 1.8–2.4 meters deep, ending in a living chamber. This shape most likely helped protect the inside from water and kept the temperature and humidity more stable.

Over time, abandoned burrows filled with sediment that hardened, while the surrounding earth eroded away. That is why stone casts of these underground structures, made by beavers millions of years ago, still survive today.