"Scientists have discovered that the original statistical model used to calculate dinosaur mass is flawed, suggesting dinosaurs have been oversized.
Widely cited estimates for the mass of Apatosaurus louisae, one of the largest of the dinosaurs, may be double that of its actual mass (38 tonnes vs. 18 tonnes)."
Dinosaurs May Have Been Smaller Than Previously Thought:
http://www.sciencedaily.com/releases/2009/06/090621195620.htm
How big was the Ophrasaurus?
Yup. More svelte.
What's a tonne?