Calamites

The calamites, or "giant horsetails" were a group of spore producing plants very closely related to modern "horsetails" (also known as "scouring rushes"), of the genus Equisetum. Much larger than modern horsetails, this ancient group also could produce wood. Trees could reach considerable heights, although those at Riola probably did not exceed 30 feet (10 m) in height, based on the sizes of the stems observed. The trunks had a hollow center that could be filled with mud after the tree died, leaving a so-called "pith cast", which is one of the most common remains of these plants. The calamites, like the modern horsetails, had "node-internode" architecture. All the leaves and branches were arranged in whorls borne at "nodes". These nodes can be seen in the fossils as lines that extend around the stem. All pictures are looking up at the roof of the mine. (Click on image for a larger view.)