Silurian period

The Silurian was a period in Earth's history. During the Silurian, the land was covered in deserts, inhabited only by huge insects, some of which were deadly. The atmosphere was high in carbon dioxide but had low levels of oxygen, due to which lifeforms from more modern time periods would be unable to survive in a Silurian environment for more than a matter of weeks at the most. Some areas of land in the Silurian were also volcanic, riddled with hidden sinkholes and plagued by seismic activity.

Real life
The Silurian period lasted from approximately 443 to 419 million years ago. During the Silurian, the climate was stable and cooling down after the Ordovician-Silurian extinction event, and jawed and bony fish were beginning to evolve and become diverse. Though life was still mainly underwater in the Silurian, a few invertebrates and other organisms had begun to take to land in the form of small terrestrial arthropods and basic shore-based plants.