Palaeocastor ('ancient beaver') is an extinct genus of beavers that lived in the North American Badlands during the late Oligocene period[1] to early Miocene.[2] Palaeocastor was much smaller than modern beavers. There are several species including Palaeocastor fossor, Palaeocastor magnus, Palaeocastor wahlerti, and Palaeocastor peninsulatus.[2]
Some members of this genus made corkscrew-shaped burrows and tunnels. Like many early castorids, Palaeocastor was predominantly a burrowing animal instead of an aquatic animal. Fossil evidence suggests they may have lived in family groups like modern beavers and employed a K reproductive strategy instead of the normal r-strategy of most rodents.
Based on size and habitat, Palaeocastor fossor has been compared to a black-tailed prairie dog (Cynomys ludovicianus).[3]
The discovery of Palaeocastor sprang from the discovery of devil's corkscrews in the plains of Sioux County, Nebraska, as a tree-sized, screw-like underground formation. Its basic form is an elongated spiral of hardened earth material that inserts into the soil as deep as 3 metres (9.8 ft). These puzzling structures first came to notice through Dr. E. H. Barbour of the University of Nebraska around Harrison, Nebraska, in 1891 and 1892.[4] Then he described it as giant freshwater sponges. This identification was influenced by the surroundings where the "screws" were situated; the deposits in which they occur were laid down in immense freshwater lakes in the Miocene Epoch, 20 million years ago. Also for a while, people tended to believe the spiral forms are a curious type of extinct vegetation, although many remained skeptical, as well.
In 1892, Dr. Barbour proposed that the devil's corkscrews were the burrows of large rodents, and Latinized the name to the ichnofossil name Daimonhelix, Daimonelix, or Daemonelix (all these spellings are found) and classified them by shape and size.[3]
This does seem to contradict an essay by Barbour in 'The American Naturalist Vol. XXIX June 1895'. Here Dr. Barbour attempts to refute a theory put forward by Dr. Theodor Fuchs, in which Fuchs states exactly that the Daemonelix was just the result of the burrowing of a Miocene Gopher. In this essay Barbour seems to be holding to the theory that the Daemonelix was the result of calcified plant forms. One argument put forward by Barbour was that the form of the corkscrew was too perfect to have been constructed by a 'reasoning creature', and must instead have been the result of plant construction (or some other lower life form). Barbour also states in this essay that the discovery of a fossilized beaver was not proof of the origin of Daemonelix, as there has also been found the bones of 'a mammal as large as a mouse'...