But some birds live in ways we haven't observed in the dinosaur kingdom. Ducks, for example, alternate between water and land habitats, able to take advantage of both.

Until now, that hadn't been seen in dinosaurs, but the discovery of a duck-like dinosaur from Mongolia may change that.

The new dinosaur, Halszkaraptor escuilliei, was announced on Wednesday in the journal Nature. The remarkably complete fossil skeleton that paleontologists analyzed indicates it was likely a semiaquatic dinosaur, able to both swim and move about on land.

"This is the first dinosaur with a lifestyle similar to aquatic birds — this indicates that these dinosaurs were able to exploit an environment that was not considered in our previous interpretation of dinosaur history," Andrea Cau, a paleontologist at the Giovanni Capellini Geological Museum of the University of Bologna, said in an email.

This finding helps establish a new subfamily of similar dinosaurs, according to the paper. Several other fossil specimens from the same region fit into this family, indicating they're part of the same small branch on the evolutionary tree.

The discovery "illustrates how much of the diversity of Dinosauria remains undiscovered, even in intensely studied regions such as Mongolia," the authors wrote.

Researchers used a scanning method that Cau, the lead author of the study, described as "the most advanced scanning technology ever done on a fossil" to collect about 6,000 GB of data on the fossil while it was still partially embedded in rock. The dinosaur lived between 71 million and 75 million years ago.

It's hard to prove that this was, in fact, a semiaquatic creature, but the specimen has several features that match those of semiaquatic and fully aquatic reptiles and birds. Its arms had structures similar to those that birds like penguins use to swim. And it had a neck like a goose's, with rows of teeth in its mouth.

But instead of webbed feet, it had claws and toes like those of theropod family, which includes velociraptors and Tyrannosaurus rex.

The dinosaur most likely fed on fish, crustaceans, and small reptiles and mammals, Cau said. The other members of this subfamily would have been a similar size.

The finding shows that there's still plenty of new history to be revealed as paleontologists scour the Earth for remains of the past.