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Images & Information
Public Domain from the United States Geological Survey (USGS); diorama by Masato Hattori and maps courtesy of Colorado Plateau Geosystems Inc.
Warm and wet (no seasons or polar ice caps)
Plentiful marine life, but no land animals
Most invertebrates first appeared in this period
First vertebrates (jawless fishes) appeared in this period
Prominent life forms - trilobites (similar to horseshoe crabs) and crinoids (sea lilies)
Warm and wet, but got colder near the end of the Ordovician period when an ice age began
Trilobites and crinoids were still around
Armored jawless fishes were common
Corals appeared, but reefs were dominated by algae and sponges
The first land plants appeared. They were moss-like and did not have leaves or deep roots.
The period ended with a mass extinction (about 80% of all species became extinct)
Many glaciers melted and sea levels raised
It was warmer near the equator and colder near the poles
Prominent life forms included large coral reefs and jawless fishes
The first jawed fish appeared
The first land animals - scorpions and millipede-like animals - appeared
Small vascular plants appeared and began covering the surface of the land
Much of the land on Earth was near the equator, so it was warm and mild
Interior portions of continents were dry; gypsum and salt deposits formed
Shallow seas were full of reefs and an abundance of life forms
Sharks became common; trilobites declined
Amphibians became the first vertebrates on land
Trees, ferns, and seed-producing plants were present
Earth was swampy, which allowed coal deposits to be formed
Mississippian (early Carboniferous) - warm and wet
Pennsylvanian (late Carboniferous) - an ice age began
Sea levels went down and up; much shallow marine life disappeared
Reptiles appeared and could lay eggs on land
Snails and insects appeared (some dragonflies had wing spans over three feet)
Forests included conifers
Deserts covered the interior of the super continent, Pangaea
Swamps and coal fields of the Carboniferous period dried up and were replaced with forests
Shallow seas decreased, so marine organisms and amphibian populations decreased
Reptiles spread across the land
The largest mass extinction ever occurred at the end of this era (96% of all species lost)
Huge volcanic eruptions, meteor impacts, and/or rapid increase in temperature may have caused the extinction
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