Tiny tyrannosaur fossil revealed

At only 2.7m (9 feet) in length, Raptorex already had the powerful jaws, puny arms and quick legs of its much larger and more famous descendant. This artist's impression is based on the fossil skeleton discovered in Inner Mongolia, China Photograph: Todd Marshall/University of Chicago

Weighing as little as a thousandth as much as T-rex, 125 million-year-old Raptorex nevertheless has the same distinctive body plan Photograph: Todd Marshall/University of Chicago

The skull of Raptorex is dwarfed by the skull of 'Sue', the famous adult T-rex who now lives at the Field Museum in Chicago Photograph: Paul Sereno/University of Chicago

The two-fingered forelimb of an adult T-rex and the very similar 20cm (8 inch) forelimb of Raptorex Photograph: Mike Hettwer/University of Chicago

Sculptors have added skin, scales and rudimentary feathers to a cast of the nearly complete skull of Raptorex Photograph: Mike Hettwer/University of Chicago

Entombed in the sediment of an ancient lake in northern China 125 million years ago, the bones of the long-legged predator Raptorex are remarkably well preserved Photograph: Mike Hettwer/University of Chicago

University of Chicago palaeontologist Paul Sereno adds the toe claw to the skeleton of Raptorex kriegsteini Photograph: Mike Hettwer/University of Chicago

Raptorex and friend, University of Chicago palaeontologist Paul Sereno – who has studied the 125-million-year-old tyrannosaur Photograph: Mike Hettwer/University of Chicago