Before the evolution of flowering plants there were the spore-producers . . . of which the fungi, mosses and horsetails remain to us today. The horsetails, in particular, were the most common plant and compose most of today’s coal beds. The dinosaurs tread upon these . . . and sheltered beneath them, for some reached heights of 100 ft!
Today, the tallest horsetails (in temperate climes), the Great Horsetail, reaches 6-7 ft, though the ones I found seldom top 4 ft (see photo at end of last year’s crop).