Extensive shallow seas existed around the Paleo-Tethys Ocean region. This allowed massive and widespread coral reefs to flourish.

While oxygen levels were rising above 25 per cent, the actual pressure in the atmosphere had probably risen to about one-tenth of its present-day value, during which time simple plants like Cooksonia started to adapt to the drier environment of land.

The first plants to take hold on land grew initially in marshy land areas with its primitive root system still embedded in the nearby water supply, and then later in the more desert-like expanses inland.

Wingless insects became the first creatures to crawl onto land, following the vegetation ashore, sometime during the end of this period, or the early Devonian Period.

 
Glaciation appeared at this time despite high levels of carbon dioxide in the atmosphere. Scientists are not too sure why. Perhaps volcanic eruptions have sent debris high in the upper atmosphere to reduce sunlight?