A fossilized brain solves a heated scientific debate

A fossilized brain discovered in 1984 provided a definitive solution to a long-running heated scientific debate.

A study conducted at the University of Arizona in the United States revealed that the fossilized brain, which is due to a worm-like animal called "Cardidiction catiniolum", helped researchers to discover the truth about the origin and formation of the head in arthropods, according to the "Middle East" website, quoting the scientific journal "Science".

The study sheds light on a detailed description of Cardidiction cateniulum preserved in rocks in Yunnan Province, southern China, and the length of the fossil is half an inch (less than 1.5 cm).

The discovered brain constitutes, according to the study, a neatly preserved nervous system for that animal, which belongs to an extinct group of animals known as the "armored lobes".

The animal lived in the Cambrian period, in which almost all major animal breeds appeared during a very short period of time between 540 million and 500 million years ago.

It is likely that this animal was moving on the sea floor using multiple pairs of smooth and short legs that lack joints for its descendants, arthropods, and the closest living relatives today are the "velvet worms", which live mainly in Australia, New Zealand and South America.

The 'Cardidiction' fossils reveal an animal with a segmented trunk in which there are repetitive arrangements of neural structures known as ganglia, in stark contrast to its head and brain, both of which lack any evidence of segmentation.

“This autopsy was completely unexpected," said Nicholas Straussfeld, a professor in the Department of Neuroscience at the University of Arizona. Because the heads and brains of modern arthropods, and some of their fossilized ancestors, have been considered fragmented for more than a hundred years.”

According to the researchers, this discovery resolves a long and heated debate about the origin and formation of the head in arthropods, the world's richest group of species in the animal kingdom, and includes arthropods from insects, crustaceans and spiders, in addition to some other lineages such as millipedes and centipedes.

"Since the 1880s, biologists have observed the distinctly segmented appearance of the torso typical of arthropods, and have essentially extrapolated this to the head, and this is how the field came to the assumption that the head is an anterior extension of a segmented torso," Strausfeld added.

'But (cardidiction) shows that the early head was not segmented,' he explained. This suggests that the brain and nerve stem likely evolved separately.”