Rebellatrix, a newfound species of coelacanth, chases down Triassic prey in an illustration.
The coelacanth (pronounced SEE-la-kanth) is a primitive, slow-moving fish that's sometimes called a living fossil, because it apparently existed largely unchanged for 320 million years.
There are 40 known coelacanth species, 2 of which are alive today. All other known coelacanths have broad, rounded tails designed for slow bursts of motion.
But Rebellatrix had a huge, forked tail and streamlined body that likely allowed the ancient fish to cruise long distances and hunt prey at high speeds, said study leader Andrew Wendruff, a biologist at the University of Alberta in Canada.
According to Wendruff, the team named the discovery Rebellatrix because, like a true rebel, "it does everything a coelacanth should not do."
Pictures: New "Rebel" Coelacanth Found
The unusual Triassic predator was built to do "everything a coelacanth should not do," its discoverers say.