"Bones upon bones, we couldn't believe our eyes," Oliver Wings, a paleontologist with the Museum fur Naturkunde in Berlin, said.
Wings and fossil turtle specialist Walter Joyce of the University of Tubingen has been working with Chinese paleontologists at the site since 2008.
"This site has probably more than doubled the known number of individual turtles from the Jurassic [era]," Joyce said.
"Some of the shells were stacked up on top of one another in the rock," he said, describing the find as what paleontologists refer to as a "bone bed."
Although Xinjiang is one of the world's driest regions, 160 million years ago it was a green place of lakes and rivers, the researchers said.
But it was still subject to seasonal drought, and one such drought likely caused the remarkable fossil find, they said.
The turtles probably had gathered in one of the remaining waterholes during a very dry period, awaiting rain that never came, the researchers said.