London – Vertebrate hand patterning first developed on fish fins, just before fish emerged from the water to colonize the land, some 380 million years ago.
This is shown by a new joint study of the Flinders University in Australia and the Universite du Quebec to Rimouski in Canada on the “Tktaalik” fossil found in 2010 in Miguasha, in the Canadian Arctic, and which is published in the magazine “Nature”.
To understand the evolution of fish in tetrapods – four-legged vertebrates to which humans belong – paleontologists study fish fossils and lobed-finned tetrapods from the Middle and High Devonian (393-359 million years ago) , the “elpistostegalianos”.
On this occasion, through computerized tomography, they obtained images for the first time of the complete skeleton of the pectoral fin of one of these last specimens, where they observed the presence of a humerus (arm), radius and ulna (forearm), rows of carpus (wrist) and phalanges organized in digits (fingers).
“This is the first time that we unequivocally discovered fingers inside a fin with rays on any known fish. Fin jointed fingers are like the finger bones found in the hands of most animals, “said John Long, professor of paleontology at Flinders University.
“This finding pushes back the origin of the fingers in vertebrates to the level of the fish, and tells us that the pattern for the vertebrate hand was first developed in the deepest evolution, just before the fish left water, “he added.
For his part, Professor Richard Cloutier of the University of Quebec said that these findings are the closest thing you can get to a true “transitional fossil”, an intermediate species between fish and tetrapods.
“The origin of the fingers is related to the development of the fish’s ability to support its weight in shallow water or for short trips on land.
The greater number of small bones in the fin allows you to have more points of flexibility to extend your weight through the fin, “he explained.
According to the researchers, these studies also provide information to understand the anatomical changes associated with breathing, hearing and feeding, as the habitat of these fish changed from water to land.
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