The term Pteridospermatophyta (or "seed ferns") refers to several distinct groups of extinct seed-bearing plants (spermatophytes). The oldest fossil evidence of plants of this type is the genus Elkinsia of late Devonian age. They flourished particularly during the Carboniferous and Permian periods. Pteridosperms declined during the Mesozoic Era and had mostly disappeared by the end of the Cretaceous Period, though some pteridosperm-like plants seem to have survived into Eocene times, fossilized  in Tasmania.