The dinosaurs might take all the glory but well before they existed there was a very important period. Laura and Ellie discuss the 'explosion' in animal biodiversity that started around 541 million years ago and how we know it happened. They also speculate on what sort of animal might be missing from the fossil record and somehow come to the strange conclusion that balloon animals might have been real.

Sources of information for the factual stuff:

• Rocks (iron) absorbed free oxygen from britannica.com
• The study suggesting that animals left the seas as their eyes evolved and got bigger was reported on quantamagazine.com
• The study on the oldest animal (the floppy sea-dwelling bath mat) was reported on inverse.com