Daemonelix - fossil beaver burrow from the Miocene of Nebraska, USA. (public display, Nebraska State Museum of Natural History, Lincoln, Nebraska, USA)

Trace fossils are any indirect evidence of ancient life. They refer to features in rocks that do not represent parts of the body of a once-living organism. Traces include footprints, tracks, trails, burrows, borings, and bitemarks. Body fossils provide information about the morphology of ancient organisms, while trace fossils provide information about the behavior of ancient life forms. Interpreting trace fossils and determination of the identity of a trace maker can be straightforward (for example, a dinosaur footprint represents walking behavior) or not. Sediments that have trace fossils are said to be bioturbated. Burrowed textures in sedimentary rocks are referred to as bioturbation. Trace fossils have scientific names assigned to them, in the same style & manner as living organisms or body fossils.

The distinctive trace fossil shown above is a Daemonelix burrow. These structures are commonly called “Devil’s corkscrews”. They are large, spiral burrows made by an ancient species of terrestrial beaver. The spiraled portion of these trace fossils is usually about 1.5 to 2 meters tall. The base of the spiraled portion merges with a subhorizontal tube. The burrows are filled with siliciclastic sediments that are better cemented compared with surrounding materials.

From museum signage:

The natural casts of the spiral burrows of primitive beavers which lived some 16 million years ago are called Daemonelix. They are shown here in their natural setting as they are exposed in the Miocene sands of western Nebraska. The cowboys and ranchers discovered these spiral burrows in the late 1800s and called the "Devil's Corkscrews". The scientific name, Daemonelix, is made up of two Greek words: "daemon", a demon or evil spirit; plus "elix", anything twisted or spiraled.

Stratigraphy: paleosol in the Harrison Formation, upper Middle Miocene