T
his chapter examines the plant life and geology of the Silurian period.
The Silurian, from 440 to 400 million years ago, was named for the
Silures, an ancient Celtic tribe of Wales, Great Britain. Many of today’s
mountain ranges were uplifted by middle Paleozoic continental collisions.
The clashing of North America with Eurasia to create Laurasia closed off the
Iapetus Sea during the Silurian. The collision formed mountain belts on the
margins of continents surrounding the ancient sea, producing intensely folded
rocks (Fig.76).
Evidence of widespread reef building by Silurian corals indicates the
existence of warm, shallow seas with little temperature variation.The tabulate
corals, comprising closely packed polygonal or rounded calcite cups or the-
cae, were another important group of reef builders. The rugose, or horn
corals,so named because of their typical hornlike shapes, were particularly
abundant in the Silurian. They were the major reef builders of the late Pale-
ozoic,finally going extinct in the early Triassic.The higher land plants were
firmly established on the previously barren continents. Eventually, creatures
crawled out of the sea to dine on them.
SILURIAN PLANTS
THE AGE OF TERRESTRIAL FLORAS