This giant lobster ancestor was once the biggest animal on Earth
About 480 million years ago, the seven foot-long Aegirocassis benmoulae swam about in the sea. The lobster-like sea creature used its flaps — swimming devices on its belly and back — and long segmented body to get around. And unlike many of its fellow its relatives, it ate plankton. This means that it had to swim with its appendages outstretched in front of its head, dragging a net-like “sieve” made of long downward-directed spines through the water.
Source:: The Verge