A bizarre sea beast with a circular mouth full of serrated teeth triggered a prehistoric arms race when it evolved eyes, new research has revealed.
Radiodonts stalked the oceans more than 500 million years ago and are one of the earliest animal types to emerge on planet Earth.
Now a new study has revealed how their big eyes gave them an edge when hunting for food, forcing their prey to adapt or die, and fuelling a surge in evolution.
While other animals at the time also had eyes, the radiodonts eyes were particularly sophisticated, giving them the edge in dimly lit areas of the ocean.