Detail of a pteridosperm, an extinct seed-producing fern-like plant. Width across image about six centimeters. Photo: H. Falcon-LangFrom the press release:
The 300 million year old forest discovered in the underground workings of a coalmine in Illinois is composed of a bizarre mixture of extinct plants: abundant club mosses, more than 40 metres high, towering over a sub-canopy of tree ferns, intermixed with shrubs and tree-sized horsetails. Nowhere elsewhere on the planet is it possible to (literally) walk through such an extensive swathe of Carboniferous rainforest.
The fossil forest is the largest ever found, covering over 10,000 hectares, an area 10 km by 10 km. The fossils preserve a unique snapshot of what tropical rainforests were like 300 million year ago.
The fossils show that the Earth's first rainforests were highly diverse and that the kinds of tree species changed across the ancient landscape. The forest dates from the Carboniferous period, 300 million years ago, when most of the world's coal resources were formed.