Dinosaurs do not cease to amaze us no longer than since the Cretaceous-Paleogene mass extinction. Now, a team of scientists from the Milner Center for Evolution at the University of Bath has discovered the fossils of a new dinosaur, Ajnabia odysseus, a duck-billed dinosaur whose remains date back 66 million years. Ajnabia was found in Moroccan rocks from the late Cretaceous, specifically in the Office Chérifien des Phosphates mines in Sidi Chennane, in the Moroccan province of Khouribga.
Ajnabia odysseus (Ajnabi means foreigner in Arabic, while Odysseus – or Ulysses – comes for the famous classic character and his convoluted journey home from Troy), was a member of the group of duck-billed dinosaurs, herbivorous reptiles that grew up to 15 meters High; but Ajnabia odysseus was only 10 feet long. Like a prehistoric pony. However, its teeth and jaws clearly mark it as a member of the hadrosaurid subfamily Lambeosaurinae, and not as a different line of dinosaurs that developed a beak through convergent evolution.
The fossils show that it belonged to Lambeosaurinae, a subfamily of hadrosaurs with elaborate bony ridges on their heads. These dinosaurs evolved in North America before spreading to Asia and Europe, but had never been found in Africa before.
Did they cross the ocean?
But how is it possible that a duck-billed dinosaur that evolved in North America ended up in Africa, which at that time in history was an insular continent isolated from deep sea lanes? It seemed completely impossible.
“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? “asked Nicholas Longrich, leader of the work that publishes Cretaceous Research magazine.” Sherlock Holmes said, once you eliminate the impossible, whatever remains, no matter how improbable, must be the truth. 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 . “
This small hadrosaur has therefore forced us to reflect on how dinosaurs dispersed between continents. Based on this finding, scientists suggest that these dinosaurs must have crossed hundreds of kilometers of open water – rafting on rubble, floating or swimming – to colonize the continent.
Just swimming
Considering it was impossible to walk to Africa, hadrosaurs were probably excellent swimmers – they had large tails and powerful legs, and their remains are often found in river deposits and marine rocks, so it is possible that they simply swam the entire length of distance that separated both locations.
“As far as I know, we are the first to suggest that dinosaurs cross the ocean,” says Longrich.
Is it an unheard of case?
Ocean crossings involving animals are clearly rare events, but have been previously observed . Thus, a turtle from the Seychelles islands also floated hundreds of kilometers across the Indian Ocean to reach Africa, even green iguanas used debris to travel between the Caribbean islands during a hurricane. Ocean crossings are also needed to explain how lemurs and hippos came to Madagascar, and there are many other examples.
“Over millions of years, events that occur once in a century are likely to happen many times,” concludes the expert.
Be that as it may, it is a succession of improbable events which “highlights the rarity of our find and, therefore, its importance”, says Nour-Eddine Jalil, of the Museum of Natural History of the Sorbonne University and also co-author of the work.
Referencia: Nicholas R. Longrich et al, The first duckbill dinosaur (Hadrosauridae: Lambeosaurinae) from Africa and the role of oceanic dispersal in dinosaur biogeography, Cretaceous Research (2020). DOI: 10.1016/j.cretres.2020.104678
