Gnetopsida

Gnetopsida, commonly known as the gnetophytes, is a group of gymnosperms historically ranked as its own class within a distinct division, Gnetophyta. Recent nuclear phylogenomic studies instead place the gnetophytes as the sister group of the pine family within class Pinopsida, and some researchers now treat the group as one of three subclasses of Pinopsida rather than as a wholly separate class. It comprises three morphologically distinct living genera, Ephedra, Gnetum, and Welwitschia, each the sole living genus of its own family, and is distinguished from other living gymnosperms by vessel elements in its secondary xylem. The earliest unambiguous fossils attributed to the group date to the Late Jurassic, with the greatest known diversity reached in the Early Cretaceous.