Timeline 358.9 to 298.9 Carboniferous – The Age of Giant Bugs

Carboniferous Swamp

This picture illustrates some of the most famous inhabitants of the Carboniferous swamp forests, such as the meganeura and various early amphibians and other tetrapods.

After hundreds of millions of years being largely restricted to the oceans. Primeval forests were rapidly crawling further inland, pumping oxygen into the air through photosynthesis. 

Despite the mass extinction of marine life towards the end of the Devonian. The first amphibians evolved from fish, insects formed from arthropods, and the first primitive trees formed.

The Carboniferous period saw the highest oxygen levels ever known, the largest insects and arachnids and climate change on truly unprecedented levels all vying for dominance in a lush rainforest world.

Highlights of the Carboniferous

  • Diversification of insects and arachnids
  • Highest ever oxygen levels
  • Evolution of the first reptiles
  • Climate change leads to rainforest collapse

Vast Swamp Forests Span a Tropical World

Carboniferous swampMary Evens Picture Library/Alamy

The Lower Carboniferous world was much warmer than it is today, and oxygen levels were rising rapidly. The poles were free of permanent ice. Sea levels also remained high, but the oceans were a very different place after catastrophic marine extinctions destroyed most of the world’s coral reefs during the Devonian.

Sharks were now the apex predators of the vast Panthalassic Ocean. Among these were the stethacanthids. 

As life recovered in the Early Carboniferous oceans, vast swathes of swamp forest colonised freshwater regions. Creating lush rainforests across equatorial regions and far beyond. Swampy rainforests covered millions of square miles of land. Their rapid and unhindered evolution continued to pump vast amounts of oxygen into the air.

Amphibians Join Terrestrial Ecosystems

archaeothyrisArthur Weasley

The archaeothyris was one of the first synapsids, and a distant ancestor to all mammals and reptiles.

The Early Carboniferous saw the continued development of true amphibians. Which continued to grow throughout the Period, eventually leading to giants like the eryops.

Later in the Carboniferous, the very first reptiles evolved. Among the earliest of them was hylonomus, whose name means ‘forest dweller’. In terms of appearance, it was akin to a gecko, albeit much larger.

Photosynthesis Leads to Supersized Bugs

Not since the Great Oxygenation Event of 2.3 billion years ago did oxygen have such a profound effect on the evolution of life on Earth as it did during the Carboniferous. With the unprecedented greening of the land came rapidly rising oxygen levels. Humans may have trouble adapting to such an oxygen-rich atmosphere today. However, it was this record high that allowed arthropods to evolve to monstrous proportions.

First among the terrifying Carboniferous creatures were giant scorpions. Among their contemporaries was the equally freakishly  giant centipedes. 

Although the first flying insects likely evolved during the Devonian Period, it was not until the Late Carboniferous that they really took off, giant dragonflys were one of the largest flying insects that ever lived.

As oxygen levels spiralled out of control, it wasn’t just giant bugs that were the horrors of the time. Forest fires are also rife, since such high levels of oxygen would allow even damp biomass to catch alight easily.


The Carboniferous began as a hot and humid world of ever-rising oxygen levels only to end with glaciations transforming the climate and redefining the course of evolution. Although the end of the period was not marked by a major extinction event as many other periods are, a great deal of species disappeared as icy deserts crept up from the South Pole into far higher latitudes. Next week, we’ll be exploring the continuation of this time of extreme climate change during the Permian Period, the last of the Palaeozoic periods and a time that ended with the near complete annhiliation of all life on Earth.

The largest trees in history grow including Yggdrasil, elder treants tend the land creating great forests.

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