Following the Late Devonian extinction, sharks filled the ecological gap left by the disappearance of the heavily armoured fish, placoderms.
The vast swamps of the Carboniferous Period enhanced the evolution of new marine and terrestrial species. Amphibans appeared, followed rapidly by the first reptiles. By the Late Permian advanced reptiles as long as 3 metres had evolved.
But then at the end of the Permian Period came the most intense extinction event ever recorded, which has been nicknamed the Great Dying.
The last remaining trilobites died out in the mass extinction event 252 million years ago. © Ryan Somma, CC BY-SA 2.0
252 million years ago.
51% of all marine families, 82% of all genera, an estimated 93-97% of all species.
Having survived 2 mass extinctions, only a few localised and specialised populations of trilobites remained. These prehistoric relatives of crabs, spiders and insects finally disappeared from the fossil record completely, bringing to an end 270 million years of trilobites roaming the oceans.
The scorpion-like eurypterids, formidable marine predators that thrived in warm shallow water, were another major group that ceased to exist. And the extinction of reef-building corals meant an entire ecosystem vanished.
Map of the world as it was 260 million years ago. The supercontinent Pangaea stretched from pole to pole, creating environmental conditions that put many species under stress. © Ron Blakey, Colorado Plateau Geosystems, Inc
Both marine and land animals were affected. Many of the early groups of insects died out, the only mass extinction that has been observed for insects.
Only land plants apparently came through mostly unscathed. Even so, forests - another major ecosystem - virtually disappeared.
A single supercontinent, Pangaea, stretched from pole to pole in the Permian Period. This huge landmass created extremely hot, dry conditions across most of the interior. By the Late Permian, global temperatures were the highest they’d ever been.
The severe conditions meant vast numbers of land and marine species were at risk. And then something happened that tipped them over the edge - one of the biggest volcanic eruptions ever.
Huge volcanic eruptions in Siberia are likely to have been a major trigger of the end-Permian extinction event.
Over the course of about 600,000 years huge volumes of viscous basalt lava poured out across Siberia, covering an area roughly 7 times the size of France.
Massive clouds of gases belched out. The sulphur dioxide caused acid rain and global cooling. But this was only short-term. The temperature increased as the eruptions injected carbon dioxide into the atmosphere and yet more escaped from coal deposits exposed in the surrounding area.
As the oceans warmed, frozen methane located in marine sediments may have melted. If so, the release of this potent greenhouse gas could have turned the planet’s temperature up even more.
As well as being devastating for marine and land plants and animals, Late Permian environmental changes created anoxic conditions in the sea. This lack of oxygen caused additional widespread extinctions because it destroyed food chains.