Ancient Fish Skull Reveals Clues to Land Animal Evolution

Scientists have examined the 380-million-year-old skull of an Antarctic fish, revealing new insights into how animals transitioned from water to land. The prehistoric fish, named *Koharalepis jarviki*, was a large predatory species closely related to the first land-dwelling animals. Researchers used advanced neutron imaging to study the fossil, which was discovered in Antarctica's Lashly Mountains.

The imaging technology allowed scientists to view the internal structures of the skull and braincase without damaging the fossil. This revealed features suited for life near the water's surface. These features included openings in the top of its skull, which may have aided in air intake. The fish also possessed a light-sensitive organ linked to day-night rhythms.

These adaptations suggest *Koharalepis jarviki* lived in shallow environments. Access to oxygen near the water's surface would have been important in such habitats. The fish's brain also shared similarities with species found at the evolutionary crossroads between aquatic and terrestrial life.

*Koharalepis jarviki* belonged to the Canowindridae family, a group of fish whose fossils are found in both Australia and Antarctica. These fish are considered close relatives of the earliest four-limbed vertebrates, known as tetrapods. Tetrapods later evolved into land animals.

Growing to about one meter in length, *Koharalepis jarviki* was likely an ambush predator. It hunted smaller animals in freshwater systems. Its relatively small eyes suggest it relied on senses other than vision to capture prey. This research provides another piece of the puzzle in understanding the evolution of vertebrates from aquatic to terrestrial life.