Until now, the four-limbed Tiktaalik or Ichthyostega were considered such animals, but as a new study showed, this hypothesis was wrong.
Scientists still disagree on exactly where life came from on Earth – some argue that in deep-water hot springs, others are more likely to believe Darwin’s theory of “a small warm lake,” writes Discover Magazine.
The essence of the “warm little lake” theory is that meteorites, which act on small bodies of hot or warm water, eventually created self-replicating RNA molecules – the first examples of organic life. However, most of them agree that complicated life comes from the oceans. But which animal was the first to make a dangerous flight to land and why?
Until now, such creatures were considered the four-limbed Tiktaalik or Ichthyostega. But in reality, arthropods have been in front of them for hundreds of millions of years, and for a very strange reason: instead of trying to get out of the water, they tried to dive into it again.
Kenneth Gass, Honorary Curator of the Department of Geology at the Milwaukee Public Museum, has repeatedly encountered references in his work to the Blackberry Hill quarry in Wisconsin, which is recognized as a Cambrian fossil treasure.
Paleontologists had three key questions on this subject: which animal was the first to leave the ocean, why it did so, and when.
“All three questions were answered on Blackberry Hill,” Gass notes.
Who left the ocean first and when?
In the 19th century, traces left in the Cambrian tidal zone were discovered in the Canadian provinces of Ontario and Quebec. Initially, they were attributed to various types of arthropods, but eventually became associated with eucalyptus carcasses, bat ancestors, and centipedes.
Initially, eucalyptus carcinogens were overlooked. Without the body fossils to which the traces are attached, much of the scientific community has simply lost interest in them. And only after Blackberry Hill the interest of scientists returned.
Unusual traces of fossils found in 2002 on Blackberry Hill by geologist James Hagadorne and colleagues have suggested they belonged to a scorpion-like arthropod. But no more convincing evidence has been found.
During his first visit in 2006, Gus found a body fossil of the eucalyptococcal Mosineia macnaughtoni in the same rock layers that contained these enigmatic fossil footprints. And two years later, Todd Gass’s son found the Rosetta Stone fossil: an eucalyptus’s tail imprint. As it turned out, the Mosineia macnaughtoni was the first animal to reach land.
Why did the animals leave the ocean?
As for the question of why the animals left the water, Gus and his colleagues have an answer to this question as well. In the Cambrian period, the Moon was placed closer to the Earth than it is now, so the tides were very strong and could penetrate very deep into the mainland.
It is noteworthy that the fossil found by Gus shows that the ancient arthropods held their tails in an unusual way. Although they may have protected their eggs in this way, no evidence of nests or eggs has been found.
Mortichnia, traces of a living organism left before his death, found in Brazil in similar animals that lived at the same time, offer a simpler explanation: the animals washed up on the shore and tried to return to the water and its strange position tail was the result of disorientation.
The strong influence of the Moon at low tide and the flow of the tide could either create waves that carry the animals inland, or leave them dry and harmless when the Moon was hiding. In any case, the ability to survive outside the water provided a significant advantage.