‘Sea monster’ fossils provide evidence of ichthyosaur migration 230 million years ago

'Sea monster' fossils provide evidence of ichthyosaur migration 230 million years ago
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Fossil experts believe they have solved a decades-long mystery: Did at least 37 school-bus-sized marine reptiles die and become buried in rock about 230 million years ago in what is now central Nevada? If scientists Smithsonian National Museum of Natural History and other institutions are true, the fossil cemetery near the old silver mine represents the first example of the most fundamental and deeply rooted migration of all animal behavior.

The bones found at the Nevada site come from a giant ichthyosaur Shonisaurusit looked like a huge, shapeless dolphin. Shonisaurus According to a new study in Current Biology, they glided barge-like thousands of miles across the ocean known as Panthalassa, an ancient version of today’s Pacific Ocean, to breed and deliver their offspring.

The find provides a rare window into the behavior of prehistoric animals, something not always captured by individual fossils. This raises the possibility that additional clues buried in sediment and soil may offer a deeper understanding of the marine reptiles that inhabited the planet long before humans.

The earliest known evidence of migration dates back more than 300 million years Bandringa shark long spoons with spoon-shaped snouts and prehistoric fish with armored plates. Today, billions of animals migrate, including species as diverse as hummingbirds and humpback whales, monarch butterflies, and blue herons.

Climate change may play a role in reports of larger-than-normal fish in unexpected areas. (Video: John Farrell, Brian Monroe/The Washington Post)

Clues from similar fossils found in other regions suggest this Shonisaurus moved from parts of present-day California, Alaska, and New Mexico to central Nevada.

If so, this behavior can relate to prehistory Shonisaurus, the largest creature to roam the oceans during the Triassic period, along with modern giants – blue whales seen with their calves in the Gulf of California today. Whales tend to migrate to warmer waters to give birth, then to colder waters that are rich in nutrients.

“Even though humans have been around for more than 200 million years, you have to think that the same ecological rules are at work. [whales and Shonisauruses]“, said Nicholas D. Pyenson, one of the authors of the new paper, who works in the paleobiology department at the National Museum of Natural History.

Not all experts in the field believe that Pyenson and his colleagues have solved the mystery of the great abundance. Shonisaurus bones in place and the absolute absence of any other ichthyosaurs.

“This study is probably not the last word, but it is a good step forward,” he cautioned Martin SanderProfessor of Paleontology at the University of Bonn, Germany, and Research Fellow at the Natural History Museum of Los Angeles County.

Sander, who was not involved in the study, added: “I’m not entirely sure. It’s a good idea, but it’s very difficult to prove.”

Skeletons Berlin-Ichthyosaurus State Park It shows that it is in West Union Canyon Shonisaurus It grew up to 50 feet, five times the length of a modern dolphin, and three large elephants weighed about 22 tons. Their offspring were only a few feet long.

Charles L. CampA paleontologist at the University of California, Berkeley, first excavated alternating layers of limestone and mudstone at the site in the 1950s. He He immediately wondered what could be the cause of the large cluster Shonisaurus skeletons

“He thought it could be a massive stranding,” said Neil P. Kelley, an associate professor in Vanderbilt University’s Department of Earth and Environmental Sciences, one of the paper’s other authors, as with whales.

However, fossil evidence refutes this hypothesis, showing the presence of skeletons settled underwater far from the coast.

An effort to explain why Shonisaurus The bones were the only ichthyosaur remains discovered at the Nevada site to date, and the scientific detective became the hero of the case. The researchers combined 3D scanning and geochemistry with more traditional tools such as museum collections, field notes, photographs and archival materials.

After eliminating other possibilities, they began to look at migration as the most likely scenario. Testing of the sediment revealed no levels of mercury indicating volcanic activity, which is believed to be the cause. the greatest mass destruction 252 million years ago.

The researchers were also able to eliminate the possibility that the deadly algae poisoned the marine reptiles.

In the end, only the migration scenario seemed logical.

“Shonisaurus definitely occurs elsewhere, so the genus had a wide geographic range, and it’s very plausible that these large individuals traveled long distances, like most large marine vertebrates today,” Kelley said. “In the future, it should be possible to collect additional data that could test the hypotheses we present in the paper, including migration.”

At least two other mysteries remain about the ancient marine reptiles called ichthyosaurs.

Sander of the University of Bonn said that, like sea turtles, ichthyosaurs were originally a kind of land animal, “but in the fossil record they appear as fully blown open ocean animals. We don’t have the right rocks to show how ichthyosaurs got to the sea.”

And time Shonisaurus Extinct around 200 million years ago at the end of the Triassic period, Kelley said, “while smaller ichthyosaurs survived into the Jurassic and beyond, the entire group died out in the Cretaceous period around 88 million years ago.” It is unclear why small ichthyosaurs survived and giants did not.

Pyenson cannot help but think that he has his final destiny Shonisaurus teaching modern blue whales and other cetaceans, many of which are now classified as endangered.

“We should want a world with these big ocean giants,” he said.

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