November 27, 2020

Dinosaurs could have crossed the ocean



The first fossils of a duck-billed dinosaur have been discovered in Africa, which suggests that dinosaurs crossed hundreds of miles of waters open to get there.

The study, published in Cretaceous Research, reports on the new dinosaur, Ajnabia odysseus, from rocks in Morocco dating from the late Cretaceous, 66 million years ago. Ajnabia was a member of the duck-billed dinosaurs, various herbivorous dinosaurs that grew up to 15 meters in length. But the new dinosaur was small compared to its relatives– At only 10 feet long, it was as big as a pony.

Duckbills evolved in North America and eventually spread to South America, Asia, and Europe. Because Africa was an island continent in the Upper Cretaceous, isolated by deep sea lanes, it seemed impossible for duckbills to get there.

The discovery of the new fossil in a mine a few hours from Casablanca was “almost the last thing one would expect in the world”said Dr. Nicholas Longrich of the Milner Center for Evolution at the University of Bath, who led the study. “It was completely out of line, like finding a kangaroo in Scotland. Africa was completely cut off by water, so how did they get there? ”

Study of Ajnabia’s distinctive teeth and jaws shows that it belonged to Lambeosaurinae, a subfamily of duckbill with elaborate bony ridges on the head. Lambeosaurs evolved in North America before spreading to Asia and Europe, but had never been found in Africa before.

By reconstructing the evolution of the duckbill, they found that lambeosaurs evolved in North America and then spread over a land bridge to Asia. From there, they colonized Europe and finally Africa.

Because Africa was isolated by deep oceans at the time, duckbills must have crossed hundreds of miles of open water, debris rafting, floating or swimming, to colonize the continent. Duckbills were likely powerful swimmers – they had large tails and powerful legs, and are often found in river deposits and ocean rocks, so they may have simply swam the distance.

“Sherlock Holmes said, once you eliminate the impossible, whatever remains, no matter how unlikely, must be the truth,” Longrich said in a statement. “It was impossible to walk to Africa. These dinosaurs evolved long after continental drift divided the continents, and we have no evidence of land bridges.. Geology tells us that Africa was isolated by oceans. If so, the only way to get there is by water. ”

In reference to this feat, the dinosaur is named “Ajnabia odysseus”. Ajnabi is Arabic for “foreigner”, and Ulysses refers to the Greek sailor.

Ocean crossings are rare and unlikely events, but they have been observed in historical times. In one case, green iguanas traveled between the Caribbean islands during a debris-washed hurricane. In another, a Seychelles tortoise floated hundreds of kilometers across the Indian Ocean to reach Africa.

“Over millions of years,” Longrich said, “events of once in a century are likely to happen many times. Ocean crosses needed to explain how lemurs and hippos got to Madagascar, or how monkeys and rodents crossed from Africa to South America. ”

But the fact that duckbills and other groups of dinosaurs are spread across continents, even at high sea levels, suggests that dinosaurs also traveled the oceans. “As far as I know, we are the first to suggest that dinosaurs cross the ocean,” Longrich said.

The international team of scientists was led by the University of Bath with researchers from the University of the Basque Country UVP / EHU (Spain), George Washington University (USA) and the Natural History Museum of the Sorbonne University ( France) / Universite Cadi Ayyad (Morocco).

Dr. Nour-Eddine Jalil, from the Sorbonne University Museum of Natural History (France) said: “The succession of improbable events (crossing an ocean by a dinosaur, fossilization of a land animal in a marine environment) highlights the rarity of our find and therefore its importance.

“Ajnabia shows us that hadrosaurs have set foot in Africa and tells us that ocean barriers are not always an insurmountable obstacle.”

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