Paleontologists have determined that ray-finned fish - the world's most diverse vertebrates - began their dominance in the oceans 66 million years ago after the mass extinction that wiped out dinosaurs from the Earth.
"The extinction marked an ecological turning point for the pelagic marine vertebrates," said professor Richard Norris and graduate student Elizabeth Sibert from Scripps Institution of Oceanography at University of California, San Diego.
They analysed the microscopic teeth of fish found in sediment cores and found that the abundance of ray-finned fish teeth began to explode in the aftermath of the extinction of the dinosaurs.
Ninety-nine percent of all fish species in the world - from goldfish to tuna and salmon - are classified as ray-finned fish.
They are defined as species with bony skeletal structures and have teeth that are well preserved in deep ocean mud.
Now there are 30,000 ray-finned fish species in the oceans, the most numerically diverse and ecologically dominant species among all vertebrates on land or in the ocean.
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Sibert and Norris said, "It is amazing how quickly fish double, then triple in relative abundance to sharks after the extinction, suggesting that fish were released from predation or competition by the extinction of other groups of marine life."
"Before the extinction of dinosaurs, ray-finned fishes existed in a state of relative ecological insignificance just like mammals on land," Sibert said.
"Mammals evolved 250 million years ago but did not become really important until after the mass extinction. Ray-finned fishes have the same kind of story."
The paper titled 'New Age of Fishes initiated by the Cretaceous-Paleogene mass extinction' appeared in the journal Proceedings of the National Academy of Sciences.