A recent study has uncovered an intriguing perspective on the evolution of brain protection in vertebrates, thanks to the discovery of a 455-million-year-old fossil fish.
Published in Nature on Wednesday, September 20th, the paper was a collaborative effort among researchers from the University of Birmingham, Naturalis Biodiversity Centre in Leiden, Netherlands, and the Natural History Museum. Their focus centered on reconstructing the skull of Eriptychius americanus.
Funded by the Leverhulme Trust, the study proposes that this ancient jawless fish, unearthed from deposits in Colorado, USA, possesses a skull structure unlike any previously observed. It fills a critical gap spanning a staggering 100 million years in the evolutionary timeline of vertebrate skull development.
Employing computed tomography, a type of x-ray technique, scientists generated a detailed 3D model of Eriptychius’s skull. This marks the first comprehensive recreation of the specimen, originally collected in the 1940s, described in the 1960s, and currently housed in the Field Museum of Natural History in Chicago.
What sets this ancient fish apart is its distinct cranial makeup: it boasts separate, autonomous cartilages enclosing the brain, a departure from the solid bone or cartilage structures observed in both earlier and later jawless and jawed fish.
While subsequent species exhibit a fully connected cartilaginous framework safeguarding the brain, these findings hint that the initial development of mechanisms to segregate the brain from other cranial components might have commenced with Eriptychius.
Dr Ivan Sansom, Senior Lecturer in Palaeobiology at the University of Birmingham and senior author of the paper said:
“These are tremendously exciting results that may reveal the early evolutionary history of how primitive vertebrates protected their brains. Eriptychius americanus appears to be the first evidence for a series of cartilages separating the brain from the rest of the head. This study emphasises the importance of museum collections and the application of new techniques in studying them.”
Dr Richard Dearden, Postdoctoral Research Fellow in Palaeobiology at Naturalis Biodiversity Center and lead author of the paper said:
“On the face of it Eriptychius is not the most beautiful of fossils. However, by using modern imaging techniques we were able to show that it preserves something unique: the oldest three-dimensionally preserved vertebrate head in the fossil record. This fills a major gap in our understanding of the evolution of the skull of all vertebrates, ultimately including humans.”
Header Image Credit : Field Museum of Natural History and Ivan Samson.