St. Louis County, Missouri
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The Salem Formation is known for well preserved teeth.
This tooth was not visible the day before a rain storm. Teeth are porous
and absorb moisture and will expand causing any thin layer of matrix
covering the tooth to crack and fall off.
The teeth (mostly broken) that I found on the ground around the limestone
didn't weather out from the shale. They weathered out of the limestone and
if these teeth were in good condition, they recently popped out of the limestone.
Teeth will not survive long when exposed to the elements.
Mississippian Fossils of Missouri