Fossilized remains of many animals of the past have been seen before, but it is not every day that we see a school of fish preserved on a millions of years old slab of rock. It is now the oldest evidence of schooling behavior in fish.
Fossilized School Of Fish
In a new study, researchers describe the discovery of the fossilized remains of extinct fish. However, this is no ordinary slab of rock with ancient fish, as it contains the well-preserved remains of a group of fish, all facing the same direction.
The fish are determined to be of the Erismatopterus levatus species because of the features of their dorsal fins, anal fins, and the base of their pelvic fin. E. levatus is an extinct species that used to live in alpine lakes, and their remains were found while the researchers were examining the fossil collections at Oishi Fossils Gallery of Mizuta Memorial Museum in Japan. In total, researchers found 259 fish in the stone.
Researchers could not specify their cause of death, but they surmise that it is possible for the fish to have died as a result of a sudden collapsing of a sand dune that trapped and killed them.
Earliest Evidence Of Fish Schooling
According to researchers, the position of the fish, in that they were all facing the same direction, suggests that they were in a school. This makes the discovery the oldest evidence of schooling behavior. Model scenarios that put water flow and spatial distribution into account show that the ancient fish likely formed schools for the same reason that modern fish do, which is to protect themselves from predators.
“These findings suggest that fishes have been forming shoals by combining sets of simple behavioural rules since at least the Eocene. Our study highlights the possibility of exploring the social communication of extinct animals, which has been thought to leave no fossil record,” researchers note.
The study is published in the journal Proceedings of the Royal Society B: Biological Sciences.