Researchers at the Scripps Institution of Oceanography found that fish diversity increased after the mass extinction of dinosaurs. This research has concluded that the end of an era for dinosaurs and most marine reptiles signified the dawn of the “new age of fish” resulting in the wide variety of fish species today.
Fish Diversity Expanded at the end of the Mass Extinction
Marine paleontologist researchers from the Scripps Institution of Oceanography combed the seafloor of the Atlantic and Pacific Oceans to find evidence of when fish diversity expanded so rapidly.
Their conclusions, published at the end of June in PNAS, revealed that sometime after the mass extinction event between 75 million and 45 million years ago, ray-finned fishes exploded in terms of diversity. They did so to fill different ecological niches that were left vacant from the many species that had died off.
Mass Extinction Said Goodbye Dinosaurs, Hello Fish Diversity
At the end of the Cretaceous period, a mass extinction decimated the dinosaur population, also knocking off many large marine reptiles and ammonites. However, it was the same event that allowed a new opportunity for other species to flourish, expanding their evolutionary success to reach great diversity.
One such group that made the most of the opportunity was ray-finned fishes. What’s a ray-finned fish? Basically any fish in the ocean with the exception of sharks and rays. Ray-finned fishes are so diverse, they make up half of all vertebrate species today.
Though it was a devastating event for the hundreds of species that were picked off the Earth, for ray-finned fishes, the end-Cretaceous mass extinction led the way for them to become major players in the evolutionary chain of events.
Fish Teeth Compared to Scale Count Shows Fish Diversity Explode
Led by Elizabeth Sibert and Richard Norris, marine paleontologists from the research team drilled into Italian limestone in two oceans to gather fossils of fish teeth and scales for analysis.
The samples of teeth from ray-finned fishes and scales from sharks and rays spanned from the late Cretaceous period to the mid-Eocene period. The researchers noted that scale count and teeth count were consistent before the mass extinction, but only the teeth count increased after the event.
Although less than a third of sharks and rays went extinct during the event, their numbers seemed to keep at a base level. In contrast, the ray-finned fishes population grew rapidly. The researchers theorized that many ecological niches needed to be filled after so many species of dinosaurs and over 90 percent of plankton species died off.
One Fish, Two Fish, Extinct Fish, New Fish – Diversity Thrives
Researchers also showed that right after the extinction, there were changes in teeth sizes with larger teeth increasing in a spike for a few million years before vanishing. Theories indicate that these probably belonged to animals that didn’t stick around too long, a sort of evolutionary experiment.
However, what did stick around was the ray-finned group. They have established their place in evolutionary history thanks to the mass extinction that allowed the huge fish diversity to continue to thrive even today.
