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(also Lyginopteridopsida or Cycadofilices), a group of ancient extinct gymnospermous plants, usually distinguished as a class. The Pteridospermae appeared at the end of the Devonian and died off in the Early Cretaceous. The few whose external appearance is known resembled modern-day arborescent ferns. (For this reason the plants were formerly thought to be ferns or cycads). The plants were heterosporous, and their microsporangia were frequently gathered into sori, as in ferns, or formed synangia. The ovules had a pollen chamber and were located on the midrib of ordinary vegetative leaves or were gathered into groups on specialized shoots. In some Pteridospermae the ovules were contained in closed or semiclosed cupules. Various members of the Pteridospermae are listed under different generic names.