Giant Horsetail Plant "bark"

Calamites sp. The other side of this 1/8" thick specimen matches the side you see here. Whether a cast or a carbonized bit of the actual plant I cannot say for certain. There are very few fossils at this site that are not straightforward impressions in the shale. While not actually trees, horsetails at the time grew up to 30m (100 ft) high. The stems were very tough and the outer shell preserved very well in many areas. The inner part of the stem is not as easy to find, although I do have some whole limb rounds. Late Pennsylvanian/Carboniferous, Lewellyn Formation, Centralia, PA