Calamites is the name assigned to these ancient plants belonging to the order of sphenopsids, also known as "articulates" because of their jointed stems.
Calamites were prolific during the Carboniferous Period (360 to 286 million years ago) and were capable of achieving heights of around 30 feet. Like their lycopod contemporaries, calamites grew even as sediments filled in around them, burying them alive, so to speak. This is evidenced by specimens showing the stem engulfing stigmaria or "roots" of other plants.
Modern descendents are small by comparison-- including varieties "horsetails" (Equisetum ) which range in size from a few inches to a few feet.
From: Plant Fossils of West Virginia, Educational Series ED-3A
West Virginia Geological and Economic Survey- 1978
William H. Gillespie
John A. Clendening
Hermann W. Pfefferkorn
