This appendage would have aided fish as they explored shallow water habits during the Late Devonian period.
Collaboration with Prof John Long and the Flinders University team began in 2014.
The scientific team behind the discovery dubbed the odd animal "the missing evolutionary link".
The only difference is that, in these advanced fishes, the digits are still locked within the fin, and not yet free moving like human fingers.
Elpistostege was the largest predator living in a shallow marine to estuarine habitat of Quebec about 380 million years ago.
The evolution of fishes into tetrapods - four-legged vertebrates of which humans belong - was one of the most significant events in the history of life. Titled "Elpistostege and the Origin of the Vertebrate Hand", the study reveals new insights about the formation and evolution of the human hand.
The complete fish fossil is 1.57 meters long and shows a complete pectoral fin skeleton for the first time in this fish species. "Now we know that before losing the fin rays and losing the scales, we started developing digits for the hand".
Tetrapods include amphibians, reptiles, birds and mammals.
Measuring about 1.6 metres from the tip of its snout to the tip of its tail, it is the most complete fossil of an ancient fish from this species ever found.
The origin of digits in land vertebrates is hotly debated.
"This finding pushes back the origin of digits in vertebrates to the fish level, and tells us that the patterning for the vertebrate hand was first developed deep in evolution, just before fishes left the water", Long said.
These back-boned animals were then able to leave the water and conquer land. In order to complete this transition- one of the most significant changes was the evolution of hands and feet.
Another piece of the puzzle was found in 1985, revealing it was a lobe-finned fish.
This is a freshwater creature that reached ten feet long but only its partial skeleton have been unearthed by scientists so far.
"These fishes-called elpistostegalians-are the ones that gave rise to the first tetrapods, so share many advanced features with early tetrapods".
Other elpistostegalian fishes include the Tiktaalik, known only from incomplete fossil specimens in the Canadian Arctic.
The find could help explain how fish first ventured onto land and changed the fate of planet Earth forever.
"It's a fish-like tetrapod or a tetrapod-like fish - a fishapod", said Cloutier, a professor at the University of Quebec at Rimouski. There are too many small bones there, meaning that the fish had a lot of flexibility in the "finger" region, but these fingers weren't optimal for bearing weight on land.
"The other features the study revealed concern the structure of the upper arm bone or humerus, which also shows features present that are shared with early amphibians. Elpistostege watsoni is not necessarily our ancestor, but it is closest we can get to a true 'transitional fossil, ' an intermediate between fishes and tetrapods".
At the time, what is now Quebec was south of the equator and Elpistostege's environment was a warm, rainy, brackish estuary.
The ancient sea creature would have fed upon several of the larger extinct lobe-finned fishes found fossilised in the same deposits in Quebec. This fossil was a prize: Although broken into 22 slabs of rock, it showed the most complete specimen of E. watsoni to date.
Some time in the distant past, a unusual new creature poked its head out of a tidal estuary and made the first steps from murky water to muddy shore to become the progenitor of everything on Earth with four limbs.
This study was funded by a Research Laboratory in Palaeontology and Evolutionary Biology at UQAR (Power Corporation Inc.).
Modern-day examples of convergent evolution are the hedgehog and the tenrec - a Madagascan animal which closely resembles the hedgehog but is totally unrelated. One is commonly found in United Kingdom gardens and the other is exclusive to the island of Madagascar.