They filled the gap in knowledge about the evolution of the skull: scientists studied the remains of an ancient fish
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Scientists “revived” a 455-million-year-old fossilized fish skeleton. The analysis of her skull gave a clue to the explanation of the evolution of animal and even human skulls. Thanks to the research, scientists have filled a gap in knowledge lasting 100 million years. The findings were published in the journal Nature, writes Science Alert. The skeleton belonged to the Ordovician jawless fish Eriptychius americanus. Scientists have studied the early development of the protective dome of the vertebrate brain. It turned out that it was more complicated than previously thought. “This fills a big gap in our understanding of the evolution of the skull of all vertebrates, including humans,” said Richard Dearden, a paleobiologist at the Naturalis Biodiversity Center in the Netherlands and lead author of the paper. Reconstruction from the bones of an ancient fish The evolution of the meninges, an important structure in all vertebrates that prevents compression of the nervous system, is poorly understood. Previously, researchers only knew that there are significant differences in the shell of jawed and jawless fish. There is a gap in the fossil record between the oldest vertebrates and modern fish. The oldest surviving three-dimensional vertebrate meninges date from about 100 million years after the first vertebrates. Jawless fishes from the Ordovician period are among the oldest vertebrates discovered to date, but little is known about their anatomy due to the lack of articulated remains (that is, a movable connection between parts). “At first glance, Eryptychius is not the prettiest of fossils. However, using modern imaging techniques, we were able to show that it preserves something unique: the oldest surviving three-dimensional vertebrate head in the fossil record,” says paleobiologist Dearden. With the help of computed tomography, scientists constructed the skull of this fish from bone fragments that were found in a rock in the Harding Sandstone in the state of Colorado in the 1940s. The scientists found that Eryptychius had a symmetrical array of mineralized cartilage in the head between the olfactory bulb and the eye area. They suggest that it may have served to protect the brain and sense organs. This is somewhat similar to the anatomy of living round-mouthed jawless fish, which have a fully connected cartilaginous cage that holds the brain. But in Eryptychius, these cartilages are not joined together in an open frame, but cover their structures separately. “The significant difference between the neurocranial anatomy of the Ordovician Eriptychius and the roundmouths or hornbills helps explain why it has been so difficult to make direct anatomical comparisons between the skulls of the two living vertebrate groups,” the researchers note. Scientists suggest that these skull features may reflect the conditions in which both jawed and jawless vertebrates evolved. “These are extremely exciting results that may reveal the early evolutionary history of how primitive vertebrates protected their brains. Eriptychius americanus appears to be the first evidence of a series of cartilages separating the brain from the rest of the head,” says paleobiologist Ivan Sansom of the University of Birmingham in the UK. . Previously, scientists did not make such reconstructions, although the remains of ancient fish were kept in the museum for a long time. Read also: Using DNA, scientists found descendants of people whose skulls were taken to Germany more than a century ago
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