Asteroid that killed dinosaurs also caused mass shark extinction, study says

BY TYLER MACDONALD
Posted on OCT 14, 2019

A new study sheds light on the effect of the dinosaur-killing asteroid on the evolution of sharks.

A new study suggests that theCretaceousPaleogene mass extinction event that killed the dinosaurs 66 million years ago also caused masscreated the current equilibrium of shark species that traverse the Earth's oceans.

The team examined the numerous shapes observed across hundreds of ancient, fossilized shark teeth to come to the conclusion that the diversity ofCarcharhiniformes, the biggest modern shark order, exploded following the mass extinction. Conversely, many Carcharhiniformes sharks went extinct.
"This is an interesting and nuanced study that adds context to the end-Cretaceous mass extinction event among two major lineages of sharks," said Neil Aschliman, an evolutionary biologist at St. Ambrose University who wasn't involved with the study.

"Studying fossil sharks is both a curse and a blessing," he continued. "Whole specimens are extremely rare because the cartilaginous skeletons of these animals don't readily fossilize. Sharks continually produce and shed fossil-ready teeth throughout their lifetime. Because of this treasure trove of teeth, we have a solid understanding of when in the geological record different groups of sharks have originated and gone extinct."

A team believes that an understanding of the timeline could be important for ensuring that today's sharks don't go extinct.

"By exploring changes in their diversity over millions of years, we might be able to assess the importance of various contributorssuch as temperature, sea-level, and prey-availabilityas key drivers of shark evolution," said Mohamed Bazzi, lead study author.

"Sharks fulfill a very delicate but important ecological role," he added. "Their demise may have terrible consequences for the health and stability of whole marine food-webs. They are also remarkable creatures that capture the public imagination, though they are sadly misunderstood."

The findings were published in Current Biology