Palaeocastor

"Devil's corkscrews"

The discovery of Palaeocastor originated with the finding of 'devil's corkscrews' in the plains of Sioux County, Nebraska. These are tree-sized, screw-like underground formations consisting of an elongated spiral of hardened earth material that penetrates the soil to depths of up to 3 meters. Dr. Erwin Hinckley Barbour of the University of Nebraska first noted these puzzling structures around Harrison, Nebraska, in 1891 and 1892. He initially described them as giant freshwater sponges, an interpretation influenced by the surrounding deposits, which were laid down in immense freshwater lakes during the Miocene Epoch, about 20 million years ago.

For a time, many believed the spiral forms were a curious type of extinct vegetation, though skepticism persisted. In 1892, Barbour proposed that the devil's corkscrews were burrows of large rodents and gave them the ichnofossil name Daimonhelix (also spelled Daimonelix or Daemonelix), classifying them by shape and size. However, an essay by Barbour in the June 1895 volume of The American Naturalist appears to contradict this. In that essay, Barbour attempted to refute a theory by Dr. Theodor Fuchs that the Daemonelix resulted from the burrowing of a Miocene gopher.

Barbour instead held to the calcified plant theory, arguing that the corkscrew form was too perfect to have been constructed by a 'reasoning creature' and must have come from a plant or lower life form. He also noted that the discovery of a fossilized beaver was not proof of the origin of Daemonelix, as bones of 'a mammal as large as a mouse' had also been found. As late as the second decade of the 20th century, the burrowing origin was not universally accepted; Theodore Andrea Cook, in 'The Curves of Life' (Constable 1914), wrote that other hypotheses remained, including one involving two plants coiling around each other, and that knowledge was insufficient for a satisfactory theory.

Did You Know?

• Palaeocastor was predominantly a burrowing animal rather than an aquatic one.
• Fossil evidence suggests they may have lived in family groups like modern beavers.
• Palaeocastor fossor has been compared to a black-tailed prairie dog in size and habitat.