The results of a micro-CT scan of the skull of a 319 myo fossilized fish unearthed in Carboniferous strata in the Mountain Fourfoot coal mine in Lancashire, England over a century ago, and first described in 1925, conducted as part of a broader project, surprised the researcher conducting as it as it showed a distinct, 3-dimensional object within the skull that possessed a number of features associated with vertebrate brains such as being bilaterally symmetrical, contained hollow spaces similar in appearance to ventricles, and had extending filaments that resembled cranial nerves.
Given the age of the specimen this meant they had discovered the oldest example of a well-preserved vertebrate brain.
The researchers think that when the fish, known as Coccocephalus wildi, died, the soft tissues of its brain and cranial nerves were replaced during the fossilization process with a dense mineral, possibly pyrite, that replaced tissue that had likely been preserved for longer in a low-oxygen environment, thereby preserving it in exquisite 3-dimensional detail.
Since this was the only known example of this creature scientists would not risk more invasive methods of investigation.
The brain and its cranial nerves are about 1" long and belong to an extinct fish roughly the size of an average modern bluegill (between 6-8" or 15.25-20.3cm), that was prehistoric ray-finned fish that swam in an estuary and likely preyed upon aquatic insects, small crustaceans, and cephalopods, chasing them with fins supported by bony rods called rays. Today, the ray-finned fish subclass Actinopterygii, make up over half of all living backboned animals, including approximately 96% of all fish.
IOW, at the very least, this discovery opens up a window into the neural anatomy and early evolution of this major group of fish.
The full paper, Exceptional fossil preservation and evolution of the ray-finned fish brain, is available by clicking the hyperlink, although I've posted the abstract from it below
Here are a few videos
Given the age of the specimen this meant they had discovered the oldest example of a well-preserved vertebrate brain.
The researchers think that when the fish, known as Coccocephalus wildi, died, the soft tissues of its brain and cranial nerves were replaced during the fossilization process with a dense mineral, possibly pyrite, that replaced tissue that had likely been preserved for longer in a low-oxygen environment, thereby preserving it in exquisite 3-dimensional detail.
Since this was the only known example of this creature scientists would not risk more invasive methods of investigation.
The brain and its cranial nerves are about 1" long and belong to an extinct fish roughly the size of an average modern bluegill (between 6-8" or 15.25-20.3cm), that was prehistoric ray-finned fish that swam in an estuary and likely preyed upon aquatic insects, small crustaceans, and cephalopods, chasing them with fins supported by bony rods called rays. Today, the ray-finned fish subclass Actinopterygii, make up over half of all living backboned animals, including approximately 96% of all fish.
IOW, at the very least, this discovery opens up a window into the neural anatomy and early evolution of this major group of fish.
The full paper, Exceptional fossil preservation and evolution of the ray-finned fish brain, is available by clicking the hyperlink, although I've posted the abstract from it below
Abstract
Brain anatomy provides key evidence for the relationships between ray-finned fishes1, but two major limitations obscure our understanding of neuroanatomical evolution in this major vertebrate group. First, the deepest branching living lineages are separated from the group’s common ancestor by hundreds of millions of years, with indications that aspects of their brain morphology—like other aspects of their anatomy2,3—are specialized relative to primitive conditions. Second, there are no direct constraints on brain morphology in the earliest ray-finned fishes beyond the coarse picture provided by cranial endocasts: natural or virtual infillings of void spaces within the skull4,5,6,7,8. Here we report brain and cranial nerve soft-tissue preservation in Coccocephalus wildi, an approximately 319-million-year-old ray-finned fish. This example of a well-preserved vertebrate brain provides a window into neural anatomy deep within ray-finned fish phylogeny. Coccocephalus indicates a more complicated pattern of brain evolution than suggested by living species alone, highlighting cladistian apomorphies1 and providing temporal constraints on the origin of traits uniting all extant ray-finned fishes1,9. Our findings, along with a growing set of studies in other animal groups10,11,12, point to the importance of ancient soft tissue preservation in understanding the deep evolutionary assembly of major anatomical systems outside of the narrow subset of skeletal tissues13,14,15.
Brain anatomy provides key evidence for the relationships between ray-finned fishes1, but two major limitations obscure our understanding of neuroanatomical evolution in this major vertebrate group. First, the deepest branching living lineages are separated from the group’s common ancestor by hundreds of millions of years, with indications that aspects of their brain morphology—like other aspects of their anatomy2,3—are specialized relative to primitive conditions. Second, there are no direct constraints on brain morphology in the earliest ray-finned fishes beyond the coarse picture provided by cranial endocasts: natural or virtual infillings of void spaces within the skull4,5,6,7,8. Here we report brain and cranial nerve soft-tissue preservation in Coccocephalus wildi, an approximately 319-million-year-old ray-finned fish. This example of a well-preserved vertebrate brain provides a window into neural anatomy deep within ray-finned fish phylogeny. Coccocephalus indicates a more complicated pattern of brain evolution than suggested by living species alone, highlighting cladistian apomorphies1 and providing temporal constraints on the origin of traits uniting all extant ray-finned fishes1,9. Our findings, along with a growing set of studies in other animal groups10,11,12, point to the importance of ancient soft tissue preservation in understanding the deep evolutionary assembly of major anatomical systems outside of the narrow subset of skeletal tissues13,14,15.
Here are a few videos
Comment