A BIG shrimp-like animal is the oldest known swimmer that sieved food out of the water, like today's krill and baleen whales.
By half a billion years ago, there were passive filter feeders like sponges sitting on the ocean floor. But palaeontologists thought that swimming filter feeders didn't arise for another 160 million years.
Jakob Vinther at the University of Bristol, UK, and his colleagues studied frond-shaped fossils from 540-million-year-old rocks. Each one has a bendy spine about 12 centimetres long, covered with 3-cm-long strands (Nature, DOI: 10.1038/nature13010 ).
They belonged to Tamisiocaris borealis, a 70-cm-long shrimp-like beast called an anomalocarid. It had two fronds on its head, which caught plankton before tucking it into the animal's mouth.
Vinther thinks it evolved from predatory anomalocarids, the top predators at the time.
This article appeared in print under the headline "Lost 'shrimp' was almost like a whale"
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