Dinosaurs Smaller than Thought

Giant Reptiles Probably Lighter and Sleeker than Assumed

Jun 25, 2009 Rupert Taylor

Scientists have found a glitch in equations used to calculate the weight of gigantic dinosaurs such as Diplodocus.

According to statistician Gary Packard of Colorado State University, “Paleontologists have for 25 years used a statistical model to estimate the body weight of giant dinosaurs and other extraordinarily large extinct animals.” In a paper published June 21, 2009 in the Zoological Society of London’s Journal of Zoology, he reveals there are problems with this technique. A mistaken use of logarithms has led to weight estimates that are much too high.

“We have found that the statistical model is seriously flawed and the giant dinosaurs probably were only about half as heavy as is generally believed.”

Packard is quoted in the U.K.’s Daily Mail (June 23, 2009) as saying: “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.”

In the article “Tiny-rannosaurus Rex: Why Dinosaurs may not have been as Big as Hollywood Films Suggest,” The Daily Mail points out that, “The ‘reference sample’ consisted of 33 species of quadruped mammals, ranging in size from a rodent weighing 47 grams to an elephant weighing almost 4,000 kilograms.”

Tyrannosaurus rex Smaller and Faster

Probably the best-known predatory species, Tyrannosaurus rex, may have been far more lithe than imagined; it’s likely it was able to turn and move a high speed.

T. rex’s prey may not have been the lumbering herbivores the public has become familiar with. EurekAlert.com (June 21, 2009) reports on the research: “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).

Other dinosaurs have also lost weight dramatically because of the new calculations. Styracosaurus has been dropped from 4,200 kilograms to 3,300 kg, and Diplodocus probably weighed about 4,000 kg rather than the previously estimated 5,500 kg.

Dinosaurs Were Still Huge Animals

Paleontologists have reconstructed many of the large dinosaurs from fossilized bones discovered on many sites. From these they have been able to fairly accurately establish the length and height of the animals. The girth is a different matter.

According to the article “Dinosaurs Shed a few Tons in Science Makeover” Times of London science editor Jonathan Leake, Packard’s research changes a lot. “Until now,” Leake wrote in his June 21, 2009 article, “(large dinosaurs) have been shown as well-rounded, powerful animals, when they are more likely to have been skinny and muscular.

“Such findings would affect more than just appearance. It would suggest that these animals were leaner and faster, needed less food and had significant differences in lifestyle from what was previously thought.”

Eurekalert.com adds that, “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 copyright of the article Dinosaurs Smaller than Thought in Paleontology is owned by Rupert Taylor. Permission to republish Dinosaurs Smaller than Thought in print or online must be granted by the author in writing.

Apatosaurus, Still Huge but Slimmer