WASHINGTON, June 21 (Xinhua) -- Dinosaurs may not have been as monstrously heavy as previously thought, because of flaws in the statistical model to calculate their weight, researchers reported on Sunday.

    Widely cited estimates for the mass of Apatosaurus louisae, one of the largest of the dinosaurs, may be double that of its actual mass, the researcher said in the Zoological Society of London's Journal of Zoology.

This artist's illustration shows a male of the medium-sized predatory dinosaur Troodon, which lived in North America in the late Cretaceous Period, brooding over a clutch of eggs.(Xinhua/Reuters Photo) Photo Gallery>>>

    Apatosaurus was said to have weighted 38 tons but its actual mass may be only 18 tons, they claimed.

    "Paleontologists have for 25 years used a published statistical model to estimate body weight of giant dinosaurs and other extraordinarily large animals in extinct lineages," lead researcher Gary Packard from Colorado State University said in a statement.

    "By re-examining data in the original reference sample, we show that the statistical model is seriously flawed and that the giant dinosaurs probably were only about half as heavy as is generally believed."

    The new predictions have implications for numerous theories about the biology of dinosaurs, ranging from their energy metabolism to their food requirements and to their modes of locomotion, the researchers said.