"In the time of the Aegirocassis benmoulae, during the the Ordovician period, plankton ecosystems were changing and many new species of plankton were popping up. This likely spurred the emergence of this large plankton-eating anomalocaridid. And going from predation to plankton-filtering is part of a larger evolutionary theme, Van Roy says. "Exactly the same thing happened much, much later in sharks and whales," he says. "They started out as predators, and because of a major plankton diversification suddenly you get extremely big filter-feeding animals, like whale sharks and blue whales." Researchers also think Crocodiles went through a similar period in which a large plankton-eating species of crocs emerged. "They reached massive sizes," he says. "And our animal is the oldest example of this."" - rønin