Definition of Sphenophyllum
: a genus of Paleozoic fossil plants that are related to the club mosses and horsetails but are usually placed in the separate order Sphenophyllales, that have jointed stems, cuneate leaves in whorls of three or multiples of three, and terminal cones or sporophylls, and that occur from the Devonian to the Permian
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Origin and Etymology of sphenophyllum
New Latin, from sphen- + -phyllum
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