When all the carbon frozen in the permafrost of Siberia is released back into the ecosystem, the Earth with once again look like a tropical paradise it once was, being able to sustain giant cold-blooded reptiles.
(Well, not sure they actually were reptiles, but most likely cold-blooded.)
That's on chapter 9, "The Conquest of Land and the Radiation of Amphibians". Caution, this is a book from 1988, the Carboniferous era may have changed a lot since then.
(Carboniferous = Mississippian + Pennsylvanian.)
An image search for "Paleozoic and Mesozoic amphibians and reptiles" may also be gratifying. I'm fond of Moschops ("calf face"), though that's after the Carboniferous rainforest collapse.
When all the carbon frozen in the permafrost of Siberia is released back into the ecosystem, the Earth with once again look like a tropical paradise it once was, being able to sustain giant cold-blooded reptiles.
(Well, not sure they actually were reptiles, but most likely cold-blooded.)