This is how a forest of Calamites and Asteroxylon may have appeared just about anywhere on the Earth 390 million years ago. The Calamites are the slender Christmas tree shaped plants. They grew as tall as many of today's conifers, though they are the ancient ancestors of the much smaller modern horsetails. The snake-like curlicue plants in the foreground are the now-extinct Asteroxylon, which emerged at the beginning of the Devonian period about 417 million years ago.