A new study has found evidence that at least one species of dinosaur may have been an expert swimmer, diving into the water like a duck to hunt its prey.
to study, published in Communications Biology on December 1, describes a newly discovered species, Natovenator polydontus. The theropod, or hollow-bodied dinosaur with three fingers and claws on each limb, lived in Mongolia during the Late Cretaceous, between 145 and 66 million years ago.
Scientists from Seoul National University, the University of Alberta and the Mongolian Academy of Sciences collaborated on the paper.
The researchers noted that Natovenator had streamlined ribs, like those of diving birds.
“Its body shape suggests that Natovenator was a potentially capable swimming predator, and the streamlined body evolved independently in separate lineages of theropod dinosaurs,” the authors wrote.
The Natovenator specimen is very similar to Halszkaraptor, another dinosaur discovered in Mongolia, which scientists believe was likely semi-aquatic. But the Natovenator specimen is more complete than the Halszkaraptor, making it easier for scientists to see the streamlined shape of its body.
Both Natovenator and Halszkaraptor probably used their forearms to propel themselves through the water, the researchers explained.
David Hone, a paleontologist and professor at Queen Mary University of London, told CNN that it’s hard to say exactly where Natovenator falls on the spectrum from fully terrestrial to fully aquatic. But the specimen’s arms “look like they would be pretty good at moving water,” he said. Hone participated in the peer review of the Communications Biology study.
In addition, Natovenator had dense bones, which are essential for animals that dive below the surface of the water.
As the authors wrote, it had a “relatively hydrodynamic body.”
The next step, Hone said, would be to model the shape of the dinosaur’s body to help scientists understand exactly how it might have moved. “Is he paddling with his feet, a bit like a puppy? How fast could it go?
Further research should also look at the environment in which Natovenator lived. The specimen was discovered in Mongolia’s Gobi Desert, but there is evidence that there have been lakes and other bodies of water in the desert in the past.
“There is a real question of, OK, you have a dinosaur swimming in the desert, what is it swimming in?” he said. “Finding the fossil record for those lakes will be difficult, but sooner or later, we may find one. And when we do, we may find many more of these things.”
Nizar Ibrahim, a senior professor of paleontology at the University of Portsmouth, whose research has included findings indicating that Spinosaurus was likely semi-aquatic, told CNN that he is still not fully convinced by the study’s findings. He would argue that a more rigorous quantitative analysis would have made the findings more convincing.
“I would have liked to see, for example, a really robust depiction of bone density, the osteohistology of the animal, within a larger data set,” he said. “Even the anatomy of the ribs, if they had put that into a bigger picture, the large data set would have been useful.”
The “anatomical evidence is less clear” for a swimming Natovenator than for a swimming Spinosaurus, he said.
And like Hone, he’s also curious as to exactly what waters the Natovenator might have been swimming in. “The environment this animal was found in in Mongolia is the exact opposite of what you would expect for a water-loving animal,” he said.
But he hopes the study can help open the door to broader ideas about dinosaur behavior. Dinosaurs were previously thought to be strictly terrestrial, but increasingly, evidence has emerged to suggest that at least some species spent as much time in the water as they did on land.
“I’m sure there will be many, many more surprises,” Ibrahim said. “And we’ll find that dinosaurs were not only around for a long time, but also, you know, really diverse and very good at invading new environments.”
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