Footprints of the 15-metre (49ft)-long Mamenchisaurus sinocanadorum, which weighs roughly 14,000kg, were found near the city of Chongqing in south-west China.
These bipedal tracks suggest the dinosaur spent more time on two legs than previously thought, and was well adapted to fast walking and running.
Dr Xing Lida of the China University of Geosciences, who led the study, said the trackways of this species have been found before - in Inner Mongolia and the Ningxia Hui Autonomous Region - but the new set are different.
"The footprints found at Chongqing are unique in that they were clearly left by a single individual, and also they record the turning behaviour of this individual," he said.
"This suggests that the speed of the individual that made the tracks was probably quite high, because we know that large animals run faster when making tight turns."
The findings are published in the journal Scientific Reports.
