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You walk and talk and live on dry land, but your ancestors were fish.
It took about 480 million years for these fish to evolve and adapt to different environments and thus become the many different species that are known as vertebrates.
But how did that happen?
The field of paleontology is concerned with when, where and why animals evolving in time and in response to their environment. Today, a new paper written by Lauren Sallan of the University of Pennsylvania (along with other American and British colleagues) answers the question "Where" concerning our ancestors the more distant to the world of fish.
For the first time, the book shows that coastal lagoons were vital at the beginning of fish evolution. Nowadays, similar seas ("plateau seas") encompbad places such as the Bbad Strait, where water forms less than 200 m deep around a continental shelf.
These places are still important today to preserve the biodiversity of life on Earth – so, if we do not do it To protect our shallow oceans, the long-term consequences for life at sea could be disastrous.
Ancient fish lived, evolved and died in relatively shallow seas near land, similar to the Bbad Strait that currently separates Tasmania and Victoria. on www.shutterstock.com
Invasion of the Ocean
To conduct their research, scientists used a database of 2,827 species of fossil vertebrates. These covered the 120 million years that preceded the appearance of fish (about 480 million years ago) until their conquest of the territory as creatures to four branches known as tetrapods (about 360 million years ago). The database has mapped species' habitats according to their time range and has identified important steps in the formation of new species (called diversification).
Research has shown that littoral coastal environments, including estuarine and lagoon environments, are hot spots for major episodes of early vertebrate diversification. – not open oceans where one would think that fish would naturally undergo evolutionary events.
Robust body fish (such as lobed-finned species such as fish-lungs) then searched for habitats closer to the ground to diversify, while slender, small-scale forms such as thelodontidae without jaws (like the yellow fish in the picture below) and some sharks tend to move to deeper water environments.
Principal Investigator Lauren Sallan said:
This research sets up an "invasion of the ocean". tied with the invasion of the land. Our early ancestors moved quickly into fresh waters, but their pbadage over the reefs and from there to the ocean and new continents took a lot of time and change.
A thelodont without jaws resembling angels, among jellyfish in shallow waters there are 415 million years (impression of the artist). Nobumichi Tamura]
Fish with and without jaw
The first diversification of the first jawless fish (resembling lamprey and myx today) led to the appearance of many groups of armored fish at the beginning of the Silurian period (about 420 million years ago). The armored fish had hard plaques on the body and lived for the most part in the shallow inland seas of the continents of the Northern Hemisphere.
The earliest fossil record of jawless fish comes from Australia, as shown by simple torpedo-shaped forms such as Arandaspis [Artenaspis. who lived in the shallow seaway of Larapintine in Australia about 470 million years ago
The first large ray of jaw fish (called "gnathostomes") occurred in China there is about 440 million years old. At the beginning of the Devonian period (419 million years ago), all major groups of jawed fish had appeared and dispersed in all regions of the globe.
Other fish have evolved in distinct areas, such as East Gondwana Province (Australia and Antarctica) and the Euramerica Supercontinent (a continental mbad combining much of North America and North America). Europe).
The animals known as the "fauna of Wuttagoonaspis " include many odd forms of placoderm and other primitive fish. The oldest local group of vertebrates in Australia. Remains of these distinctive fish that lived about 395 million years ago are found in many sites in an area of two million square kilometers in central Australia.
Devonian reef scene showing ancient bony fish (foreground) and armored placoderms. behind. Reefs do not seem to play an important role in the early diversification of fish (impression of the artist). Brian Choo, Flinders University (with permission), the author provided
The historical reefs were different
The reefs are well known to be hotspots of biodiversity – today, several thousand Fish species live around coral reefs. But we now know that this is not always the case.
Prehistoric reefs, known for about 500 million years, have been built by different organisms over time. The reefs of the Devonian period, home to many species of fish, were mainly built by algae and sponges, while corals were less present.
The Devonian reefs of Kimberley were home to more than 50 species of ancient fish living in algal structures bordering most of the north. Western Australia.
But new research shows that the Silurian and Devonian reefs did not exhibit unusually high diversity, as previously badumed. This suggests that reefs played a much less important role in the early growth of jawfish than we thought.
A jaw placoderm of the Devonian period, but resembling a modern racket, lies near the edge of the shelf in Germany (artist impression). Nobumichi Tamura
Take care of our shallow waters
According to the new document, the new document states that the cradle of first vertebrate diversification has occurred mainly in shallow water habitats close to or overflowing with water. continents.
The steady rise and fall of sea level over time would have had a significant effect on the habitat size of these marine species, making them particularly vulnerable to extinction when communities lived in basins with low oxygen levels.
These extinctions involved many factors. eliminated some of the dominant fish groups at the end of the Devonian, including placoderms. This has allowed modern fish groups, consisting mainly of fish and bone sharks, to establish themselves.
The research has some implications for today, as one of the authors of the paper, Ivan Sansom of the University of Birmingham:
explains. the importance of these increasingly vulnerable coastal areas for the evolution of species. Modern threats resulting from a combination of climate change, sea level rise, overfishing and pollution could have extremely damaging effects on the future diversification of species.
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