Andrew Wendruff from the University of Alberta says his one-metre-long, forked-tailed coelacanth was an 'off-shoot' lineage that lived 240 million years ago.

Wendruff's coelacanth is named Rebellatrix, which means rebel coelacanth. The researchers say Rebellatrix came along after the end-Permian mass extinction 250 million years ago, an event so lethal it wiped out 90 per cent of marine life. Rebellatrix filled a previously unoccupied predator niche, but it didn't fare well.

Wendruff's research co-author, U of A Professor Emeritus Mark Wilson, describes typical coelacanths as having chunky bodies, fins of varying size and broad, flexible tails. "These fish were slow-moving and probably lay in wait for their prey," said Wilson.

"Rebellatrix was likely a spectacular failure in the evolution of cruising predation," said Wendruff. "Clearly some other fish groups with forked-tails must have outperformed this coelacanth as it does not appear later in the fossil record.

The fossil, which is the most complete so far found of the species, has been outlined by two scientists from the University of Alberta in the Journal of Vertebrate Paleontology. The species, which had a huge symmetrical tail, which is very different to any other coelacanths, has been placed in its own family. The fossil was found on the sloped of the Hart Ranges of the Canadian Rockies, in Wapiti Lake Provincial Park, British Columbia. The fish swam to the west of the Pangaea supercontinent.