The first fish originated in marine waters near the coast

The first fish originated in marine waters near the coast https://i1.wp.com/www.eresviral.com/wp-content/uploads/2018/10/Los-primeros-peces-se-originaron-en-aguas-marinas-cerca-de-la-costa.png?fit=260%2C40&ssl=1

The first fish originated in marine waters near the coast







The first vertebrates on Earth were fish, and scientists believe they first appeared about 480 million years ago. But the fossil records are irregular and only small fragments have been identified. Some 60 million years later, 420 million years ago, the fossil record shows something completely different: a great variety of fish species en masse.



But where were the fish really? Where did they originate? A team of scientists, led by Lauren Sallan of the University of Pennsylvania in the US, has tried to answer these questions in a study published in the journal Science.



Until now the scientific community presumed that the first fish were developed in coral reefs, given the great biodiversity of fish that currently exists in these ecosystems, but the search for decades in these places has not yielded results.



The group of scientists analyzed the fossils of vertebrates from the Middle Paleozoic (between 480 and 360 million years ago), as well as the environmental markers that indicate their ancient habitats. With this information the researchers created a database with 2,728 early records for fish with jaws and without jaws. "It's a really great new data set," says Sallan.







Recreation of a Bothriolepis, an armored placodermo that lived mainly on the coast. (Photo: Nobumichi Tamura)



The results indicate that all major groups of early vertebrates, including fish with and without jaws, originated and diversified in intertidal and subtidal environments near the coast, over a period of 100 million years.



"Our work shows that from the first armored fish without jaws to sharks or even our own ancestors they started near the beach, away from the reefs and further inland. As the older groups expanded, the newer ones also appeared on the coast, "says Sallan, lead author of the work and paleobiologist at the American university.



These findings help to fill the void that existed in the understanding of the early diversification of vertebrates, since until now they had little exploration of the ancient habitats in which they lived.



The team was able to reconstruct incomplete information from the fossil record using mathematical models, which allowed making predictions about the type of habitat in which the first ancestors of several vertebrate groups emerged.



"For vertebrates, we find that they originate in this shallow and unexpected area of ​​the oceans, and remain in this limited area for a long time after they emerge," she stresses.



As these populations near the coast diversified, adaptations in body patterns allowed them to spread to other environments. According to the authors, the strongest creatures remained in near-shore or freshwater habitats, while those with more graceful bodies colonized the deeper waters to avoid increased competition, as the nearby shallow and confined habitats to the coast they were full of life.



These new explanations in the fossil record also allow us to understand the fact that, over time, many groups of fish moved from the ocean to fresh water, while others evolved into the first tetrapods, terrestrial vertebrates.



"They often flocked to fresh water before going to the reefs, which is almost an independent line of evidence that they should have been close to shore before doing so," says Sallan.



Currently, no one has conducted a similar comprehensive study on living vertebrate species. "One of the things we want to know is if these shallow waters are still the biological pump that feeds the reef," says Sallan.



If that were the case, there could be some small consolation for the massive deaths of reefs around the world. According to the scientists, it is possible that these shallow waters continue to be the cradle of fish diversification, allowing biodiversity to persist despite the scarcity of reef habitats. (Source: SINC)

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