Scientists discover ancient oceanic reptile that evolved extremely quickly

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Scientists have unearthed a skull from a fossil-rich region of northern Nevada that reveals striking answers about ocean life – past and present.

What’s up – In a study published Thursday in the newspaper Science, researchers identified a new species of ichthyosaur – a huge fish-shaped marine reptile that emerged 250 million years ago shortly after the Permian mass extinction wiped out most of the life on Earth.

The new species is nicknamed Cymbospondylus youngorum – a massive creature comparable in size to the largest animal on Earth today: the blue whale.

The researchers’ findings provide fascinating insight into the rapid evolution of the huge bodies of ichthyosaurs from similarly sized cetaceans, a class of marine animals that includes whales.

“We discovered that ichthyosaurs and whales, two iconic groups of giant ocean predators that both evolved from terrestrial ancestors, evolved into gigantism in very different ways,” he added. Lars schmitz, study co-author and associate professor of biology at Claremont McKenna, recounts Reverse.

Massif skull C. Youngorum alongside one of the researchers for the scale. Martin sander

How they made the discovery – Researchers identified the new species of ichthyosaur from bones found in an area of ​​northern Nevada known as the Fossil Hill Fauna.

The fossil is a very large skull, found with a few other specimens of C. youngorum.

After analyzing the old bones, the researchers both estimated the animal’s body size and built a phylogenetic tree to determine how quickly their bodies evolved compared to whales.

Finally, they used mathematical models to try to trace how food webs might have supported large animals like C. youngorum so early in the Mesozoic period.

What they found – Scientists say this C. youngorum Clocked at a massive weight of over 80,000 pounds and had a body length of over 59 feet. His skull alone is 6.2 feet long, the size of an adult man.

“No other group of vertebrates seems to have developed gigantism so rapidly” Nicolas pyenson recount Reverse. Pyenson is Curator of Fossil Marine Mammals at the Smithsonian and co-author of a related article regarding the study.

The massive creature lived about 246 million years ago. Other large land animals would not appear until 40 million years later, with the arrival of the sauropod dinosaurs in the Jurassic Period.

The body shape of the new ichthyosaur was remarkably similar to that of modern whales, although whales evolved nearly 200 million years after the ancient marine reptile.

But what was even more impressive was the fast nature of ichthyosaur evolution. In just three million years after their origin – or the first percent of its evolutionary history – some species of ichthyosaurs had evolved to over 55 feet in length.

A study graph showing the rapid changes in body size of a) ichthyosaur compared to b) cetaceansCourtesy of the researchers

Compare that with the whale, which also evolved into gigantism much later in its evolutionary life.

“When we look at the evolutionary history of whales, it took most of their 50 million year history to grow to the gigantic body sizes of fin whales, blue whales, sperm whales and right whales,” says Schmitz .

“The big surprise here is that the ichthyosaurs are the ones who reached gigantism quickly.”

This development is also remarkable because it occurred shortly after the Permian mass extinction or the “Great Death” that killed most animals on Earth.

“We believe that the terrestrial ancestors of the ichthyosaurs became seafarers [animals] after this extinction, and reaching the large size this rapid is impressive ”, Lene delsett, a paleontologist working at the Smithsonian and co-author of a related article on the study, says Reverse.

Given that the ichthyosaur would dominate Earth’s oceans for another 150 million years before going extinct, its gigantism was clearly an evolutionary advantage.

The massive skull of C. Youngorum – a creature that quickly evolved into one of the dominant ocean animals during the Mesozoic period. Natalja Kent

Why is this important – Researchers have long argued that the size of ocean creatures during the Mesozoic Period (66-252 million years ago) was limited by the lack of primary producers like plankton, which provide energy and, for example, therefore, from food to creatures higher in the food chain. .

This study blows this theory out of the water, suggesting that Mesozoic ocean ecosystems were more than capable of supporting large animals like the ichthyosaur. The results provide unprecedented insight into these early ocean ecosystems.

“We infer that early Middle Triassic pelagic ecosystems (244 million years ago) could surprisingly support several large oceanic tetrapod consumers,” the researchers write.

But the results are also important for a larger, non-scientific audience. Since the study finds analogies between now extinct ichthyosaurs and modern marine life, we would do well to pay attention to the implications of these similarities, lest we also want today’s ocean giants to disappear.

Pyenson writes:

“The evolution of ichthyosaurs tells us that ocean giants are not guaranteed features of ocean ecosystems, and that we need to understand the threats and solutions to keep the giants today by our side.”

Failure to learn from the ancient marine past could doom the ocean ecosystems of the present.

“We should be concerned about the plight of the ocean giants, as many of today’s largest whales are ecosystem engineers and contribute to the health and productivity of the oceans that we need for ourselves,” adds Pyenson.

And after – The findings, in turn, could prompt further research on not only ichthyosaurs and whales, but “also other vertebrate animals that have come back to life at sea such as mosasaurs and the like,” says Schmitz.

Further studies could help explain the ecological conditions behind the evolution of oceanic gigantism that paleontologists see in the fossil record.

“The only thing the fossil record tells us over and over again is that if the environmental conditions aren’t quite right, we sometimes see a dramatic loss of species,” says Schmitz. But there is a big caveat.

“On the other hand, if the environment allows it [it], life is becoming more diverse, not only in the number of species but also in terms of anatomical and ecological diversity, ”adds Schmitz.

Thus, environmental clues shedding light on the evolution of various modern marine ecosystems – and the giants that inhabit them – may still be hidden in the earth’s crust.

Summary: The body sizes of marine amniotes span six orders of magnitude, but the factors that have governed the evolution of this diversity are largely unknown. The high primary production of modern oceans is considered a prerequisite for the emergence of giant cetaceans, but this condition cannot explain the gigantism in Triassic ichthyosaurs. We describe the new giant ichthyosaur Cymbospondyus youngorum sp. nov. with a 2-meter-long skull from the Middle Triassic Fossil Hill fauna of Nevada, USA, highlighting the rapidly changing size despite the absence of many modern primary producers. Surprisingly, the fossil hill fauna rivaled the composition of modern marine mammal faunas in terms of size range, and energy flow models suggest that Middle Triassic marine food webs were able to support several large ichthyosaurs at large. high trophic levels shortly after the origins of the ichthyosaurs. .

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