麻豆淫院

A pair of researchers, Guillaume Guinot and Fabien Condamine, both with Universit茅 de Montpellier, in France, has looked at the impact of the Cretaceous鈥揚aleogene (K-Pg) extinction event on elasmobranch species to learn more about survival of marine creatures during extinction events. In their study, published in the journal Science, the marine biologists collected and analyzed data for thousands of fossil species that were living during the Late Cretaceous鈥揚aleocene era.

Scientists have learned a lot about what happened after the Chicxulub impactor crashed into the Earth approximately 66 million years ago. The violent impact and its aftermath led to widespread extinction of approximately 55% to 76% of all the planet's creatures鈥攊ncluding all of the non-bird dinosaurs. But most findings involve the impact on land-based ecosystems鈥攎uch less is known about what happened to the sea life. In this new effort, the researchers focused their effort on just one subclass of cartilaginous fish鈥攖he elasmobranch鈥攁nd how it fared in the aftermath of the K-Pg event.

Elasmobranch species include sharks, rays, skates and sawfish. To learn about what happened to them after the massive asteroid strike, Guinot and Condamine scoured information in datasets around the world describing elasmobranch fossil specimens that have been found and studied over the years. In particular, they were looking at survival rates to find patterns that might shed light on how they endured.

They found that the number of species of elasmobranch overall declined by over 62% following the asteroid strike, and some species of elasmobranch had higher survival rates than others. They found that rays did better than sharks鈥攐verall, 72% of ray species survived, while only 59% of sharks did.

More specific results included the discovery that rays that fed on shellfish did not fare well; neither did older species of sharks. Combined, they had an extinction rate of 72%. On the other hand, species that lived in the higher latitudes and lived over large geographic ranges not only had higher initial survival rates, but also recovered more quickly than other species.

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