Most people picture dinosaurs when they think about Earth's ancient past. Yet the most bizarre chapter of our planet's history came long before the first dinosaurs appeared. Around 350 million years ago, Earth looked like an alien world. Massive swamps stretched across the continents under a thick, oxygen-rich atmosphere. This strange environment gave rise to creatures that would seem impossible today - insects grew to monstrous sizes, with dragonflies as big as hawks and millipedes longer than cars.
