More than 500 million years ago in the Cambrian period there was an explosion of animal life. The top predators were from a group called the Anomalocarids, the largest animals of their day. But now, a new fossil suggests that not all the Anomalocarids were the fearsome killing machines scientists once thought. At least one, it seems, evolved into a gentle giant.
Read the paper:
http://www.nature.com/nature/journal/v507/n7493/full/nature13010.html
Cambrian animations:
http://burgess-shale.rom.on.ca/ 