Image caption
Around the time of the Paleocene-Eocene Thermal Maximum, much of the continental United States had a sub-tropical environment. This fossil palm is from Fossil Butte National Monument, Wyoming. Image courtesy U.S. National Park Service.
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Around the time of the Paleocene-Eocene Thermal Maximum, much of the continental United States had a sub-tropical environment. This fossil palm is from Fossil Butte National Monument, Wyoming. Image courtesy U.S. National Park Service.