The asteroid that killed the dinosaurs also helped the sharks to evolve
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In the oceans of our planet are home to more than 500 species of sharks, from tiny to huge sharks-goblins and other monsters. And, the current balance of species of sharks that we see today originated after the mass extinction the Cretaceous-Paleogene period 66 million years ago, according to a new study. In the Cretaceous period (which was between 142 million and 66 million years ago) over seas commanded a detachment lunoobraznye sharks Lamniformes. Modern lunoobraznye sharks include great white, Mako and hammerheads.
However, studying the various shapes of hundreds of ancient fossil shark teeth, the researchers found that a variety margarinefabrik sharks Carcharhiniformes is the largest group of sharks today, including tiger sharks and others began to develop rapidly, while lunoobraznye sharks extinct. This balance has been preserved to our times.
theWhat is left of the sharks?
"the Study of fossil sharks is a curse and a blessing," says Neil Eshleman, an evolutionary biologist from the University of St. Ambrose, who did not participate in the study. "Complete copies is extremely rare, because the cartilaginous skeletons of these animals are poorly fossilized. Sharks continually produce and lose teeth throughout their life. Actually, because of this treasure with the teeth we have a clear understanding of when in the geological record appearance and disappearance of different groups of sharks".
After Analyzing the various forms 597 ancient sharks teeth from around the world, Dating back to 56 — 72 million years ago, scientists came to the conclusion that the extinction of one group of sharks and the prosperity of the other was associated with a change in diet and food sources. Lunoobraznye ate a lot of squid, and marine reptiles, but many of them died. Small bony fish, on the other hand, began to flood the sea and become food for margarinefabrik shark that was hunting them.
The Study of the evolution of sharks is helping scientists find ways conservation of modern species that are under threat of destruction.
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