Teredo Petrified Wood
North Dakota designated teredo petrified wood as the official state fossil in 1967 (one of the first states to recognize a fossil symbol). Teredo petrified wood is unique because of the "worming" of the original wood by the prehistoric teredo - a worm-shaped mollusk related to modern clams, mussels, and oysters. 60 to 80 million years ago, the teredo was burrowing through trees growing near the edges of warm swamps in North Dakota during the Paleocene Epoch.
Naming of the Teredo petrified wood as the state fossil promoted the fossil to tourists, geologists, and rockhounds, and caused the Smithsonian Institution to represent North Dakota in its mineral collection. Petrified wood is also a symbol of Washington, Louisiana, and Texas.