North Dakota State Fossil - Teredo Petrified Wood

In 1967 the North Dakota state legislature designated teredo petrified wood as the North Dakota state fossils. Teredo wood the name that is given to wood that was bored into by small, worm-shaped marine mollusks of the genus Teredo, commonly known as shipworms. Thus, petrified teredo wood would be the fossils of this wood bearing these distinctive boreholes.

Teredo petrified wood showing the distinctive boreholes of Teredo shipworms that have been filled in with while chalcedony.
Teredo petrified wood showing the distinctive boreholes of Teredo shipworms that have been filled in with while chalcedony.


During the Paleocene period (approximately 60 million years ago) parts of North Dakota were covered by warm water swamps, similar to Florida today. Sequoias and other trees growing in these swamps fell into the water and were washed out to sea become driftwood. This driftwood was then bored into by the marine shipworms. Under the right conditions this driftwood would become fossilized and replaced with silica through the process of permineralization.

Teredo petrified wood is a common fossil in the Cannonball formation which outcrops in Morton County, North Dakota.



Petrified wood is also the state fossil of Louisiana, Arizona and state stones of Texas and Washington.

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