A 50-million-year-old fossil captures a swimming school of fish
This snapshot in time reveals that fish may have coordinated their motion long ago
Fossilized fish captured mid-swim offer a rare glimpse into extinct animal behavior — and suggest that swimming in schools developed at least 50 million years ago.
A limestone shale slab from the Eocene Epoch reveals that extinct, thimble-sized fish called Erismatopterus levatus may have coordinated their motion similar to how fish in groups move today, researchers report May 29 in Proceedings of the Royal Society B.
The fossil captures a mass of 259 fish apparently swimming in the same direction. It’s unclear what killed the fish. But a suddenly collapsing sand dune, for example, could have buried them in place in a flash, knocking just a few askew in the process, the researchers suggest.
Analysis of the fish’s positions and orientations suggests they followed the same rules of “attraction” and “repulsion” that govern fish shoals today: The fish are repelled from their nearest neighbors to avoid collisions, but stick with the group by tracking with farther away fishes.