Scientists have discovered a new species of dinosaur that they believe originated in Mongolia 75 million years ago.
The strange turkey-sized, bird-like creature boasted a swan's neck, arms resembling flippers, long legs and lived in on rivers and lakes.
Study leader Andrea Cau, a paleontologist at the Capellini Geological Museum in Bologna, Italy, said the dinosaur, named Halszkaraptor escuilliei, walked on two legs on land in an upright ostrich-like posture.
He said it also spent a lot of time floating on top of the water, using its long neck to catch small fish, insects, molluscs and crustaceans.
"It combines different features from different groups of dinosaurs in an unexpected and bizarre mix," said Cau.
"It looks like a mixture between a Velociraptor and a goose."
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The dinosaur's semi-aquatic lifestyle is almost unheard of.
A fossil was poached from a site in southern Mongolia and sold to private collectors before being spotted by French dealer Francois Escuillie, who acquired it and provided it to researchers.
Scientists used a sophisticated scanning device called a synchrotron to peer inside solid rock to make out anatomical details of the well-preserved, nearly complete fossil skeleton.
The researchers believe Halszkaraptor, a close cousin of the dinosaur lineage that led to birds, was covered in feathers, although no feathers were found.
University of Alberta paleontologist Philip Currie, another of the researchers, added: "In water, it probably was a slow-moving swimmer, perhaps similar to a swan.
"Halszkaraptor was able to run like all dinosaurs, and probably hunted its prey using an ambush strategy that used the long neck to quickly catch small animals."
Its snout was low and slender, contributing to its bird-like appearance.
"I would guess that it had a lifestyle similar to a shorebird or heron," Currie said.
Its name honours Escuillie and late Polish dinosaur expert Halszka Osmolska.
The research was published in the journal Nature.