In 1825, Robert Brown separated gymnosperms from gymnosperms. The father of botany, Theophrastus, first used Gymnosperm in his Inquiry into Plants. Gymnosperms originated in the Devonian Period of the Paleozoic Era 300 million years ago and spread across the globe during the Mesozoic Era. The tallest trees in the world are Hyperion (Sequoia, Sequoia sempervirens) and General Sherman or Redwood Tree (Sequoia, Sequoia gigantea). The oldest tree, the bristlecone pine, is a gymnosperm. Zamia pygmaea is the world’s smallest gymnosperm.