The ancient burrowers of the seafloor have been getting a bum rap for years.
These prehistoric dirt churners -- a wide assortment of worms, trilobites, and other animals that lived in Earth's oceans hundreds of millions of years ago -- are thought to have played a key role in creating the conditions needed for marine life to flourish. Their activities altered the chemical makeup of the sea itself and the amount of oxygen in the oceans, in a process called bioturbation.