It had a graceful, swan-like neck but bizarre "killer claws" that could tear prey to shreds: The fossil of a new, 75-million-year-old species of "duck dinosaur" has been discovered in Mongolia, paleontologists reported Wednesday.

The fossil represents a new species of amphibious dinosaur, one that walked on two legs on land like ducks, but also used its flipper-like forelimbs to maneuver in water like penguins. It also relied on its long neck for foraging and ambush hunting.

The scientific name of the creature is Halszkaraptor escuillie (nicknamed "Halszka"), which honors Polish paleontologist Halszka Osmólska, who was known for her study of Mongolian dinosaurs.

The dinosaur is a strange combination that hasn't been seen before. "The first time I examined the specimen, I even questioned whether it was a genuine fossil," says Andrea Cau of the Geological Museum Capellini in Bologna and lead author of the study, which appeared in the British journal Nature.

"It is so unusual and bizarre compared to most of the known dinosaurs," he said. "It combines a duck-like head with a swan-like neck, short arms with bizarre hands and a velociraptor-like body."

Noting that it's the first bird-like, semi-aquatic dinosaur, Cau said: "Halszka represents a new ecological niche for dinosaurs."

Although it could run and swim, the dinosaur was not able to fly.

The critter was about the size of a goose, making it one of the smallest-known dinosaurs. Its diet consisted mainly of fish and crustaceans, but it also ate lizards and insects, he said.

And since it lived at the same time as the ferocious velociraptor, Halszka was likely a frequent dinner entree for that infamous dinosaur.

The fossil was found at Ukhaa Tolgod in southern Mongolia, which has been known by paleontologists for decades and is often targeted by poachers. Illegally exported from Mongolia, it resided in private collections around the world before it was acquired in 2015 and offered to paleontologists for study and to prepare its return to Mongolia.

"Illicit fossil trade presents a great challenge to modern paleontology and accounts for a dramatic loss of Mongolian scientific heritage," said study co-author Pascal Godefroit of the Royal Belgian Institute of Natural Sciences in Brussels.

Paleontologists used multi-resolution, X-ray microtomography to study the fossil. "This technique is currently the most powerful and sensitive method to image internal details without damaging invaluable fossils," said Paul Tafforeau of the European Synchrotron Radiation Facility, another study co-author.

Thanks to this state-of-the-art technique, Cau said "we now demonstrate that raptorial dinosaurs not only ran and flew, but also swam."