The scientists studied the Australian lungfish Neoceradotus and found that one of its fin-sprouting genes also guided the growth of digits in land vertebrates.
The gene helped shape the hands, feet and wings of every land animal alive, the researchers said.
"People have found comparable genes and gene-expression patterns in the fins of ray-fin fishes and also sharks, so it seems like the pattern goes very, very deep in vertebrate history," said study team member Zerina Johanson, a palaeontologist at the Natural History Museum in London.
The development of fingers and toes in embryos of land animals is closely linked to a gene called Hoxd13.
This gene orchestrates a series of developmental steps involving the sequential release of certain proteins that affects the outer part of the limb and the digits but not the arm bones. It was once thought that digit development was unique to tetrapods, creatures that have, or once had, fingers and toes.
The new finding, however, suggests this is not the case.
Johanson and her colleagues found that the genes involved in creating the Australian lungfish's fins made proteins in a nearly identical pattern as in tetrapods, by acting on the small fin bones but not the rest of the limb.
"Due to the similarities, we can say that fish fins have similar structures to tetrapod digits, [and that] tetrapod digits are no longer unique to the group," said Johanson.
The findings are scheduled for publication in an upcoming issue of the Journal of Experimental Zoology, reports Live Science.