Oldest fossils of remarkable marine reptiles found in Arctic
WASHINGTON: Ichthyosaurs were a successful group of marine reptiles that flourished during the time of the dinosaurs, some reaching lengths of nearly 70 feet (21 meters) – the largest in the history of Earth’s oceans among only whales. Their size was huge.
But their origins have been somewhat mysterious. Fossils Discovered from a harsh and remote location dating back nearly 250 million years—the Norwegian Arctic island of Spitsbergen—now provides surprising insights into the rise of ichthyosaurs.
Researchers said they found the remains of the oldest known ichthyosaur, which lived nearly 2 million years after Earth’s worst mass extinction that ended the Permian period, which swept the globe between massive Siberian volcanoes. Wiped out about 90% of the species on Earth.
The 11 tail vertebrae discovered indicate that the animal was about 10 feet (3 m) long, making it an apex predator.
Like whales, which are mammals, and various reptiles that live in Earth’s oceans, ichthyosaurs evolved from ancestors that walked on land and migrated from land to sea.
Researchers thought that any ichthyosaur that lived 250 million years ago would be a primitive form, not far removed from its land-dwelling predecessors. Fossils show it, which has not yet been given a scientific name, was physically quite advanced.
“The real surprise was that, after geochemical, computerized microtomographic and microstructural analyzes of the bones, the vertebrate emerged from a highly developed, fast-growing, probably warm-blooded, large body at about 3 meters in height. long, and a completely marine ichthyosaur,” said Benjamin Kerr, curator of vertebrate pocket science at Uppsala University’s Museum of Evolution in Sweden and lead author of the study published in the journal Current biology.
“The implications of this discovery are manifold, but most importantly it suggests that the long-anticipated transitional ichthyosaur ancestor may have appeared much earlier than previously suspected,” Keir added.
In light of this discovery, it is possible that ichthyosaurs may have originated as early as 20 million years before the mass extinction event, Kear said. The Triassic period followed by the mass extinction was its inaugural event. Age of the DinosaursAlthough the earliest dinosaurs did not appear until about 230 million years ago.
The site where the fossils were found is a classic arctic landscape with high snow-capped mountains along the shores of a deep fjord. These fossils were exposed by melting ice along river channels that cut through layers of rock that were once mud on the ocean floor. While there are polar bears and beluga whales in Spitsbergen today, 250 million years ago the sea there would have been full of fish, sharks, shelled squid-like ammonoids and crocodile-like marine amphibians called temnospondyls.
Mass extinctions shake up terrestrial and marine ecosystems and open opportunities for new species to fill ecological roles vacated by extinct species. Ichthyosaurs quickly became dominant and persisted until about 90 million years ago.
Many ichthyosaurs looked like dolphins, except with vertical rather than horizontal tail flukes. Others resembled large whales. The largest include Shastasaurus, at about 70 feet (21 m). They ate fish and squid. Fossils show ichthyosaurs giving birth to their young.
Until now, the oldest member of the ichthyosaur lineage was a 16-inch-long (40-cm-long) creature called Cartorhynchus that lived 248 million years ago in China.
In recent decades researchers have identified early forms of whales, including an ambulocetus, dubbed the “walking whale” because of its intact limbs that allowed it to still roam on land. Is.
“Most interestingly, the mysterious ‘walking’ ichthyosaur ancestor is undoubtedly still waiting to be uncovered,” Kerr said. “Only now we have to start looking at even older rocks, which is exactly what we’ll be doing on our next fossil-hunting trip to Spitsbergen this summer.”