Cambrian Explosion: a new article on early brains (Introduction)

by David Turell , Monday, December 23, 2019, 01:19 (1798 days ago) @ David Turell

Found quite definitively in another Cambrian animal:

https://www.livescience.com/new-athropod-fossil-brains-found.html

"Scientists discovered these splotchy marks in fossils of the arthropod Alalcomenaeus, an animal which shares its phylum with modern insects, spiders and crustaceans. The animals lived during the Cambrian period, which took place between about 543 million and 490 million years ago, and sported a tough exoskeleton that fossilized well. But the soft tissues of the creature's brain and nerves often decayed and therefore disappeared from the fossil record.

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"Besides Ortega-Hernández and his team, only a handful of researchers have reported finding fossilized nervous tissue in Cambrian-period arthropods. In a 2012 paper, scientists described the first evidence of a fossilized arthropod brain, in a tiny creature called Fuxianhuia protensa. Although widely covered in the media, the report attracted critics.

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"In their study, Ortega-Hernández and his co-authors uncovered a new Alalcomenaeus fossil buried in Utah within a region of geological depressions known as the American Great Basin. The authors noted symmetrical stains along the creature's midline that resembled nervous system structures found in some modern arthropods, including horseshoe crabs, spiders and scorpions. "The nervous system and the gut kind of cross each other, which is really funky but common in arthropods nowadays," Ortega-Hernández told Live Science.

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"The stains also contained detectable levels of carbon, a key element in nervous tissue. The dark splotches also plugged into the animal's four eyes, as would be expected for nervous system tissue. Having checked all these criteria, Ortega-Hernández said that he could confidently report finding fossilized nervous tissue in the newfound specimen.

"But to double-check their findings, the authors also examined a second Alalcomenaeus fossil from the American Great Basin. Originally dug up in the 1990s, the specimen sported similar stains and carbon traces to the newfound fossil. What's more, both Great Basin fossils matched descriptions of another specimen that Strausfeld found in China. All three fossils had been found buried in similar deposits, indicating that a unique preservation process allowed all their brain matter to fossilize, Ortega-Hernández said.

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"More work must be done to clarify the role of sediment in fossil preservation, but as of now, ample evidence suggests that arthropod remains placed under intense pressure solidify over time, Strausfeld said. The brain and nerves within the animal flatten out in the process, and because nervous tissue contains lots of fat, the structures repel water and "have some resistance against decay," he said.

"Despite the evidence in their favor, Ortega-Hernández, Strausfeld and their colleagues may need to dig up a lot more arthropod brain bits to convince naysayers that ancient brains can fossilize."

Comment: Some scientists may be doubtful, but logic tells us if eyes are present and limbs that must have moved are found, there was a nervous system to run the show. And this means, most significantly, a complete nervous system appeared with no precursors. Darwin's cAmbrian gap strikes again!!