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."
When Wendruff first examined a fossil Rebellatrix in 2009, "I didn't believe what I was seeing," he said.
It was "only when I found a second, third, and fourth ... that I realized we had something real and something significant."
Photograph courtesy Andrew Wendruff and Mark Wilson
Built for Speed
The largest known Rebellatrix specimen (pictured) shows that the predator was more than 3 feet (0.9 meter) long. That's not unusual for coelacanths, which can grow up to 5 feet (1.5 meters) long, Wendruff said.
Based on the known specimens, it seems Rebellatrix first appears in the fossil record about 250 million years ago—immediately after the Permian extinction, when 90 percent of life on Earth was snuffed out by an unknown cause.
The massive loss of life "possibly left a gap in this lifestyle" of fast-moving ocean predators, allowing Rebellatrix to fill that role, Wendruff speculated.
Photograph and illustration courtesy Andrew Wendruff
The Rebellatrix fossils were collected in the 1950s and '80s on the rocky slopes of Wapiti Lake Provincial Park (pictured) in British Columbia, Canada.
This area was the western coast of the supercontinent Pangaea at the time Rebellatrix swam the seas.