The Carboniferous, a geologic period from 360 to 300 million years ago, was the hayday of the ferns. Most of the coal was formed in this period, so we were in fact burning fossil ferns... It is also in the Carbon period that animals started to live on land, the success story for the Amphibians as dominant vertebrates, later followed by Reptiles and Mammmals. Anthropods, invertebrates with an external skeleton, like insects and crabs, were also very common, and in general much larger than today.

Ferns are still abundant in New Zealand, because of the climate, but maybe also because the islands got isolated from the rest of the world. Ferns did not have to compete so much with more 'modern' plants, so we still find large tree ferns, reminding of the fern and horse-tail forest in the Carboniferous.