Marine biologists have scoured sea floor sediments for decades, finding living creatures in the mud but never fossils in the process of forming. That's because when a sea creature dies, its carcass is totally recycled within weeks. So, if a creature's soft parts are going to fossilize, it has to happen extremely fast.

The area surrounding what is now Wuda, Inner Mongolia, once teemed with tropical plants before a tremendous ancient volcanic explosion overwhelmed it. The ash-entombed forest, buried between coal layers, left such remarkably preserved fossilized plants that artists and paleontologists have been able to reconstruct the former wet-forest landscape.