OK, it's a fossilized rain forest found in a coal mine, but it's still in Illinois.

Giant Fossil Rain Forest Discovered

that's pretty interesting...however the insect/animal part appeared rather "dreamed up".

Not really. After all, the ancestral species to todays animals and plants were larger. Consider the wooly mammoth to the elephant, the saber-toothed tiger to todays bengal and siberian tigers, and the 30-40 foot crocs to todays 12-20 foot crocs. Consider the 300 foot tall redwoods of California to today's oaks and elm, etc. It would be consistent that earlier insects were significantly larger than today's variety.

that, and fossils have been found in other strata of that timeframe. They know what lived in that era and how big it was.

I may not have read far enuf into the article..I just noticed they said they only found bits and pieces.