What is the earliest vascular plant believed to have arisen during the Silurian period 410-420 mya?
Vascular plants have been the dominant land vegetation for over 400 million years and have been continually evolving in response to climatic and environmental change. The earliest vascular plants, the rhyniophytes, were small, naked, simply branched, without roots or leaves. They gave rise to 2 groups that flourished in the early Devonian (410-392 million years ago): zosterophylls, usually covered by soft spines; and trimerophytes, tending to complex branching and a shrubby habit. Several new groups of land plants evolved in the middle (392-375 million years ago) to late (375-353 million years ago) Devonian. Zosterophylls gave rise to a once-diverse group of plants that bore leaves that evolved from enlarged spines: CLUB MOSSES and their relatives, including giant scale trees (Lepidodendrales). The trimerophytes, on the other hand, gave rise to a far greater number of descendant groups, all deriving leaves from modified branching systems: HORSETAILS, with whorled appendages; FERNS, wit
