The shape of the brain could also help provide clues about arthropod evolution.
That’s because the brains of this group of insects, arachnids and crustaceans have puzzled researchers for more than a century.
To collect live science, Monday (5/12/2022) ancient worms which is known as Cardiodictyon catenulumit was discovered in 1984 along with several other fossils at a site in the Chinese province of Yunnan.
The worm-like creatures belonged to the phylum Lobopodia, a group of extinct ancestors of seafloor arthropods with armored shells and stubby legs that were abundant during the Cambrian Period (541 million to 485.4 million years ago).
So, in a new study, a team of researchers reanalysed the fossil specimens and found that the creatures harbored a startling secret: a preserved nervous system and brain.
“To our knowledge, it is oldest brain fossil we know, so far,” study lead author Nicholas Strausfeld, a neurologist at the University of Arizona in Tucson, said in a statement.
It took scientists nearly 40 years to find the brain of C. catenulum, because researchers previously believed the animal’s soft tissue had been lost over time.
But recent research has changed that bias.
Researchers have previously found primitive brain fossils in a 500-million-year-old relative of the penis worm, a 520-million-year-old sea monster, and dozens of three-eyed sea creatures from about 506 million years ago.
Evolution of arthropods
While it was surprising to find an ancient brain, the researchers were more surprised by the shape and structure of the creature’s skull.
The head and brain are both unsegmented, meaning they are not divided into sections. But the side of the body of the fossil is divided into several segments.
“This anatomy is completely unexpected,” says Strausfeld.
For more than a century, researchers have thought that the brains and heads of long-extinct arthropods were segmented like modern arthropods.
Most fossils of other ancient arthropod ancestors also have segmented heads and brains, he adds
Even more surprising, C. chain it has tiny bundles of nerves, known as ganglia, that run throughout its segmented body.
As a result of this discovery, the researchers believe that the segmented brain and head seen in modern arthropods may have evolved independently of the rest of the nervous system, which most likely segmented first.
However, the researchers note that the brain is a fossil C. chain it still shares some characteristics with modern arthropod brains, indicating that the basic shape of the brain hasn’t changed too drastically in the last half-billion years.
The researchers then want to compare the fossilized brains with those of other groups of animals, to try to reveal more about how different brains diversified over time.
The study was published Nov. 24 in the journal Evolution of arthropods.
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