Via Smithsonian:
Smithsonian paleontologist Bill DiMichele and colleagues Howard Falcon-Lang (University of Bristol), John Nelson and Scott Elrick (Illinois State Geological Survey), and Phil Ames (Peabody Coal Company) discovered the remains of one of the world's oldest tropical rainforests, preserved in the ceiling of a coal mine 250 feet below the surface. Their discovery was recently published in the journal "Geology" entitled “Ecological Gradients Within a Pennsylvanian Mire Forest.”
The rainforest extends over more than four square miles as the roof of two adjacent underground coal mines in eastern Illinois. This may be the largest single-time-period fossil forest found in the fossil record.
