According to paleontologists, the fossil is the missing link in the transition between fish and tetrapods – animals that have four limbs.
The 380 million-year-old fossil of a fish of the genus Elpistostege, found in Miguasha, far east of Canada, has revealed new clues about how the human hand evolved from fish fins. In a study published in Nature, the finding is the missing link in the transition between fish and tetrapods – animals that have four limbs.
With 1.57 meters in length, the fossil is the first to have the complete skeleton of the “arm” (pectoral fin) among all elpistostegalian fish.
Analyzing the skeleton from computed tomography scans, researchers at Flinders University, Australia, and the University of Quebec at Rimouski, Canada, noticed the presence of the humerus (arm bone), radius and ulna (forearm bones), rows of carpus (bones of the wrist) and phalanges organized in digits (like fingers).
“It is the first time that we have unmistakably found fingers attached to a fin on any known fish. The digits articulated on the fin are like the bones of the fingers present in the hands of most animals, “explained John Long, one of the researchers, in a statement.
“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.”
According to the most accepted theory today, the evolution of fish led to the emergence of tetrapods, and this was one of the most significant events in the history of life, as vertebrates managed to get out of the water and populate the land. For this to happen, one of the most significant changes was precisely the evolution of the hands and feet.
As Richard Cloutier, co-author of the article, explained, the origin of the digits is directly linked to the development of the fish’s ability to support its own weight in shallow water, or on short walks across the land. This is because the increase in the number of bones also provided more flexibility to the fins, something essential for supporting their own weight.
“The other features the study revealed concerning the structure of the upper arm bone or humerus, which also shows features present that are shared with early amphibians,” said Cloutier. “Elpistostege is not necessarily our ancestor, but it is closest we can get to a true ‘transitional fossil’, an intermediate between fishes and tetrapods.”