WASHINGTON (Reuters) - A strange turkey-sized, bird-like dinosaur that boasted a swan’s neck, arms resembling flippers, long legs and a mouth full of needle-like teeth staked out a unique amphibious lifestyle in rivers and lakes about 75 million years ago in Mongolia.

A dinosaur, named Halszkaraptor escuilliei, a turkey-sized, bird-like dinosaur that boasted a swan's neck, arms resembling flippers, long legs and a mouth full of needle-like teeth staked out a unique amphibious lifestyle in rivers and lakes about 75 million years ago in Mongolia is seen in this artist's reconstruction image released on December 5, 2017. Courtesy Lukas Panzarin/Handout via REUTERS

Scientists on Wednesday described the dinosaur, named Halszkaraptor escuilliei, which walked on two legs on land in an upright ostrich-like posture but spent a lot of time floating atop the water, using its long neck to catch small fish, insects, mollusks and crustaceans.

“It combines different features from different groups of dinosaurs in an unexpected and bizarre mix,” said study lead author Andrea Cau, a paleontologist at the Capellini Geological Museum in Bologna. “It looks like a mixture between a Velociraptor and a goose.”

Its semi-aquatic lifestyle is almost unheard of among dinosaurs.

The researchers believe Halszkaraptor, a close cousin of the dinosaur lineage that led to birds, was covered in feathers. But feathers are rarely preserved in fossils and none were found.

Compared to birds, its forelimbs were relatively small, and structurally were “decidedly not wing-like,” said University of Alberta paleontologist Philip Currie, another of the researchers.

“In water, it probably was a slow-moving swimmer, perhaps similar to a swan, and used its forelimbs to maneuver while swimming,” Cau said.

The 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.

“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. It was also able to swim and hunt in water, using again an ambush strategy thanks to its long and flexible neck,” Cau said.

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.

It is noteworthy not just for its weirdness but for the circuitous route it took before being examined by scientists.

The fossil was poached from a fossil site in southern Mongolia and sold to private collectors before being spotted by French fossil dealer François Escuillié, who verified its authenticity, acquired it and provided it to researchers. The fossil will enter the collection of a Mongolian scientific institution.

Its name honors Escuillié and late Polish dinosaur expert Halszka Osmolska.

The research was published in the journal Nature.