Archaeopteris was a plant that was both tree-like and fern-like, growing to 10 metres (33 ft) in height. Archaeopteris quickly spread throughout the world, from the equator to subpolar latitudes.

The shed organic matter altered the freshwater environment, slowing it down and providing food. This promoted freshwater fish.

Archaeopteris formed the first forest by being the first known species to cast shade due to its fronds and forming soil from its roots. Archaeopteris was deciduous, dropping its fronds onto the forest floor. The shade, soil, and forest duff from the dropped fronds created the first forest.