93 million years ago, climate change turned sharks into open-water apex predators

By Jordan Strickler | ZME Science |

ZME SCIENCE - Modern sharks, those apex predators of the open ocean, might have actually evolved from bottom-dwellers during a significant episode of global warming millions of years ago. A new University of California, Riverside (UCR) study published in Current Biology has unveiled the adaptive fin morphology of sharks in response to historical climate changes.

Approximately 93 million years ago, massive volcanic eruptions released enormous amounts of carbon dioxide, creating a greenhouse climate that dramatically raised ocean temperatures. This environmental upheaval caused some shark species to adapt to the rising temperatures by elongating their pectoral fins. This evolutionary progression changed them from stubby bottom dwellers to proficient open-water swimmers.

The study involved precise body length measurements and fin dimensions from over 500 living and fossilized shark species.

“The pectoral fins are a critical structure, comparable to our arms,” said Phillip Sternes, a UCR biology doctoral student and the paper’s first author. “What we saw upon review of a massive data set, was that these fins changed shape as sharks expanded their habitat from the bottom to the open ocean.”

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