Sharks evolved into feared predators after hot temperatures forced them closer to the ocean's surface.
Sharks became ocean predators as they moved closer to the water's surface
The creatures lived in the depths of the sea until a large outpouring of volcanic lava 93 million years ago sent ocean temperatures soaring, reducing oxygen levels at the bottom of the water and forcing the sharks to relocate.
Once they had moved nearer to the top, the sharks evolved longer and thinner pectoral fins which meant they were able to swim more efficiently - giving them more energy to expend on hunting down prey.
Phillip Sternes, an expert at the University of California, Riverside, said: "Rising temperatures drove some shark species into the open water system, which not only changed how they look but also likely had effects on the entire marine ecosystem.
"The pectoral fins are a critical structure, comparable to our arms. We saw that these fins changed shape as sharks expanded their habitat from the bottom to the open ocean."