Fossilized fish reveals the oldest surviving vertebrate brain

A 319-million-year-old fish fossil recovered from a coal mine in England over a century ago has revealed the oldest example brain well-preserved vertebrates,

A CT scan of the fossil, which uses x-rays to reveal internal features, has shown that the creature’s skull contains brain and cranial nerves about two centimeters long. The discovery is published in Nature.

Researchers from the University of Birmingham (UK) and the University of Michigan (USA) believe the discovery opens a window into the anatomy of the nervous system and the early evolution of an important group of modern fish: the radiant-finned fish.

Their findings shed new light on soft tissue preservation in fossils backbone animals. Most animal fossils in museum collections are formed from hard body parts such as bones, teeth, and carapaces.

“Unexpected Find”

Lead author Sam Giles of the University of Birmingham notes that “this is an unexpected discovery brain The three-dimensionally preserved vertebrates give us an amazing insight into the nervous anatomy of ray-finned fishes. This tells us about a more complex pattern of brain evolution than only living species suggest, allowing us to better determine how and when today’s teleosts evolved.”

“Comparisons with live fish have shown that brain Coccocephalus is very similar to brain sturgeon and paddlefish, which are often referred to as ‘primitive’ fish because they diverged from all other living ray-finned fish over 300 million years ago,” he adds.

The brain analyzed by CT is from Coccocephalus wildi, a primitive bream-sized ray-finned fish that swam in the estuary and likely fed on small crustaceans, aquatic insects and cephalopods, a group that today includes squid, octopus and cuttlefish.

In fish with striped fins, the spine and fins are supported by bony bridges called rays. Soft tissue like the brain decomposes quickly and rarely fossilizes, but when this fish died, the soft tissue brain and the cranial nerves were replaced in the process of petrification by a dense mineral that retained its three-dimensional structure in great detail.

The only known specimen of its kind

Lead author Matt Friedman of the University of Michigan notes that “an important takeaway is that these types of soft parts can be preserved, and they can be preserved in fossils that we have had for a long time: it is fossil which has been known for over 100 years.

this skull fossil it is the only known specimen of its kind, so only non-destructive methods could be used during UM-led research.

Lead author Rodrigo Figueroa, also from the University of Michigan, notes that “this fossil outwardly plain and small, it not only shows us an ancient example brain fossilized vertebrates, but also shows that much of what we thought about the evolution of the brain only from living species will have to be reworked.”

Scientists didn’t look for brain when they examined the skull fossil for the first time, but instead discovered an unusual and distinct object inside. This mysterious object had several features typical of the vertebrate brain: it was bilaterally symmetrical, contained hollow spaces that looked like ventricles, and had many filaments leading into openings in the brain that looked like cranial nerves that ran through the brain. these channels in living species.

As he explains, the brain of Coccocephalus folds inward, unlike what happens in all striped fish, which have brain unfolds.

Although preserved brain tissue has rarely been found in vertebrate fossils, scientists have had more success with invertebrates. There are about 30,000 species of ray-finned fish, which is about half of all vertebrate species. The other half is divided between terrestrial vertebrates—birds, mammals, reptiles, and amphibians—and less diverse groups of fish, such as jawless and cartilaginous fish.

Probably it was a predator

The Manchester Museum (UK) provided the University of Michigan with a fossil skull of a coccocephalus. It was recovered from the roof of the Mountain Fourfoot mine in Lancashire and was first scientifically described in 1925. fossil it was found in a layer of soapstone adjacent to the mine’s coal seam.

The Manchester Museum (UK) loaned the skull to the University of Michigan. fossil from “Coccocephalus”. It was recovered from the roof of the Mountain Fourfoot mine in Lancashire and was first scientifically described in 1925. It was found in a layer of soapstone adjacent to a coal seam in a mine.

Although only the skull was recovered, scientists believe that C. wild size was between 15 and 20 centimeters. According to Figueroa, judging by the shape of his jaw and teeth, he was probably a carnivore. When the fish died, it was probably quickly buried in low oxygen sediment. These environments can slow down the destruction of the soft parts of the body.

As the researchers note, fossil fixes the time before the evolution of a characteristic feature of the brain of ray-finned fish, indicating when this feature developed.

(According to Europa Press)

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Fernando Carvallo selects information and shares his vision of national and international news. subscribe to our Las cosas newsletter, as they should be reading your daily columns.