Sphenopsida – Relatives of the Horsetails

Modern horsetails all belong to the genus Equisetum and are distant relatives of the ancient tree- like Calamites and the vine-like, understory Sphenophyllum. Calamites grew to about 30-feet tall and, like today’s horsetails, preferred moist lake or river shorelines. Both reproduced by spores that were shed from cones hanging from branch tips. There were 11 different types of sphenopsids in the Mazon Creek flora, growing toward the mouth of the delta.