Ray-finned fishes , also called actinopterygians, are the most diverse group of these animals – and of all vertebrates – in both fresh and salt water.
In fact, there are currently an estimated 30,000 species of these bony fish . After them, the most varied are the cartilaginous, with about 1,100 species , among which are sharks and rays, which, for the most part, live in the oceans. For decades, zoologists have wondered why the former have been better able to spread through different habitats.
For some experts, they simply have a more suitable anatomical configuration . Now, a team of paleontologists from the University of Zurich argue that they benefited from a series of climatic catastrophes and the mass extinctions associated with them.
In an article published in the journal Biological Reviews , these scientists detail how they analyzed the changes in biodiversity that took place during the Permian and Triassic (PT), between 300 and 200 million years ago, a period marked by the Great Dying. This event, which lasted only a million years, wiped out about 96% of marine species and 70% of terrestrial vertebrates.
Based on this analysis and the data obtained from different species of cartilaginous and bony fish that have lived in the past two centuries, the researchers found that the latter not only better surpassed other extinction processes that occurred previously, but also became enormously diversified. after the Great Dying. This was the case, for example, of the Neopterygians, which include thousands of species nestled in dozens of orders, some apparently as different from each other as carp and eels.
During the Triassic, many of these fish developed morphological specializations in their dentitions , jaws, fins and reproductive system, which allowed them to adopt new forms of locomotion – some even jumped over the water, like flying fish – and even gave birth. young just like viviparous animals. In contrast, cartilaginous fish did not overcome these extinctions as well, so that they never fully recovered from those that occurred during the Permian.
“Our study indicates that these processes played a determining role in the development of the current marine fauna,” explains Carlo Romano, from the Paleontological Institute and Museum of the University of Zurich, who participated in the trial. “Most of these crises are associated with global climatic changes, massive volcanic activity or other natural phenomena that caused a sharp decrease in the water level.”
