Huge marine creatures that lived more than 500 million years ago evolved from hunting large prey into feeding off plankton just like modern whales, the journal Nature reported.
A team led by Jakob Vinther, a palaeobiologist at Britain's University of Bristol, discovered the fossils of Tamisiocaris borealis in Greenland in 2009.
The shrimp-like creature lived in the Cambrian period, the first of the six periods of the Paleozoic Era.
Scientists examined the fossils and concluded that the creatures had sharp claws used to catch prey.
"Researchers suspect that the animal evolved from grasping large prey to filtering smaller prey in an evolutionary arms race with other top predators. By changing its feeding strategy, T. borealis no longer needed to compete with the fiercest animals in the ocean for its food supply," Nature said.
The creatures ate much like modern whales, which have a system for filtering plankton out of the tons of water they ingest.
T. borealis, which lived between 480 million and 520 million years ago, used fins on both sides of its body to swim and catch prey.
"These primitive arthropods were the sharks and whales of the Cambrian period," Vinther told Efe. EFE