Halszkaraptor escuilliei

This is a reconstruction of Halszkaraptor escuilliei. The small dinosaur was a close relative of Velociraptor, but in both body shape and inferred lifestyle, it more closely recalls some water birds like modern swans. (Lukas Panzarin, with scientific supervision from Andrea Cau)

A newly discovered dinosaur is so strange that scientists initially thought the fossil was fake after it was found in a dealer's shop in France.

The turkey-sized cousin of Velociraptor has paddle-like front limbs and other features that suggest it spent a large part of its time in the water — making it unique among its known relatives.

"It's a real enigma," said Philip Currie, a University of Alberta paleontologist who was part of the international team that described the new species in a study published Wednesday in Nature.

The fossil appears to have been stolen by poachers from the Ukhaa Tolgod fossil bed in Mongolia sometime in the last 15 years, said Currie, who has spent decades studying the fossils of carnivorous dinosaurs from Mongolia.

It was illegally exported and probably spent time in private fossil collections around the world before it was found in a dealer's shop in France by another fossil dealer named François Escuillié.

fossil synchrotron

(Left to right) Pascal Godefroit, Andrea Cau, and Paul Tafforeau set up the Halszkaraptor escuilliei fossil for 3D scanning at the European Synchrotron Radiation Facility. (P.Jayet/ESRF)

Currie describes Escuillié as a responsible fossil dealer who always keeps his eyes open for specimens that he knows will be of interest to science. He had previously found the missing skull and feet of a dinosaur called Deinocheirus mirificus, allowing paleontologists to finally solve a decades-old mystery of what the dinosaur looked like and where it fit in the dinosaur family tree.

Then in 2015, Escuillié spotted another unusual and interesting fossil and reported it to Pascal Godefroit, a paleontologist at the Royal Belgian Institute of Natural Science in Brussels. It's the only European institution authorized by the Mongolian government to legally acquire Mongolian fossils exported to Europe.

Godefroit invited Andrea Cau, then a PhD student at the University of Bologna, to collaborate on a study of the fossil. When Cau, lead author of the study, first saw it, he was "shocked and excited at the same time," he recalled in an email to CBC News. "It was such a beautiful and unexpected fossil, completely different from all known predatory dinosaurs."

It was so strange that the first time he examined it, he questioned whether it was a genuine fossil, especially given its history.

"It is known that many fossils in private collections are, at least partially, restored to be more appealing and good-looking," Cau wrote.  

Real or fake?

Because the researchers suspected it might be something poachers assembled from a bunch of different specimens of different species, they decided to do a careful check. They took 3D-scans of the fossil, which was still embedded in the rock, using x-ray beams from the European Synchrotron Radiation Facility.

Halszkaraptor escuilliei

The Halszkaraptor escuilliei fossil is scanned during a synchrotron tomography experiment at the ESRF. The scan confirmed the fossil was genuine. (P. Jayet/ESRF)

Not only did the scans confirm the fossil was real, but they showed some bizarre features that couldn't be seen directly, such as the needle-like teeth inside its snout – many more than are typically found in related carnivorous dinosaurs. The snout also contains structures similar to those found in crocodiles' snouts. In crocodiles, they house pressure sensors to detect water movement while hunting.

Heron-like paddler

One of the dinosaur's other unusual features include an extremely long neck – "it's almost half the distance between the back of the skull and back of the hips," Currie says.

"Then we've got real weird things with the front arms."

Its arm bones are flattened, and longest finger is on the outside, making the limbs paddle-like, and suggesting it was a swimmer. Its hind limbs look more typically for a land-dwelling bird.

"In that way it looks more like a heron," said Currie, who suggests the dinosaur may have spent a lot of time wading at the water's edge, waiting for fish or amphibians to swim by, and dove when it needed to.

Snout scan Halszkaraptor

Vincent Fernandez and Vincent Beyrand of ESRF, two of the paper's co-authors, study the unusual snout of Halszkaraptor, which contains many more teeth than that of related dinosaurs and some features typically found in crocodiles. (P.Jayet/ESRF)

Now that scientists have a complete skeleton, they've realized that a partial skull and skeleton and some foot and leg bones from two other fossil beds belong to the same family of dinosaur.

The new species has been named Halszkaraptor escuilliei, after the late Polish paleontologist Halszka Osmolska, who studied Mongolian dinosaurs, and fossil dealer François Escuillié who found the fossil.

After being properly studied, the fossil will be repatriated to Mongolia.