Dinosaurs May Have Been Smaller Than We Thought: New Study

June 25, 2009

(PhysOrg.com) -- For millions of years, dinosaurs have been considered the largest creatures ever to walk on land. While they still maintain this status, a new study suggests that some dinosaurs may actually have weighed as little as half as much as previously thought.

In the study, published this week in the Journal of Zoology, Geoffrey Birchard, associate professor of environmental science and policy at George Mason University, was part of a team which uncovered a problem with the statistical model used by some scientists in the dinosaur community to estimate the mass of .

"The original equation used by scientists produces fairly accurate results when determining the mass of smaller animals, but when used on larger animals our research shows that many errors have occurred," says Birchard. "The new equation shows that dinosaurs are much smaller than we thought, but there is no mistaking that they were indeed huge animals."

Developed in 1985, the results of the original equation have been used by scientists to estimate or evaluate a variety of parameters, including and egg size. The problem occurs as a result of transforming the data, which changes the properties of the original data, and creates biases that can affect the predictive results obtained from the equation.

Birchard and his colleagues realized there was an error when they used the equation to determine the weight of living animals such as a hippopotamus and an elephant and discovered that the equation greatly overestimated the weight of these .

The researchers developed a new equation for calculating dinosaur mass based on bone dimensions. This equation doesn't require the transformation of data that the original equation uses.

"The best way to understand the new equation is to think about a building that is built on pillars,"
says Birchard. "The bigger the building, the larger the pillars must be to support the weight of the building. In the same way, the legs of an animal are the pillars supporting its body."

According to Birchard, this new research suggests that some dinosaurs were much more slender than had been thought. It also changes many of the factors scientists have already determined about dinosaurs such as the amount of muscle required to use their bodies and how much they ate and breathed.

More information: "Allometric equations for predicting body mass of dinosaurs" is published in the .

Source: George Mason University

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2 / 5 (4) Jun 25, 2009
Smaller dimensions, or lighter, i.e lower mass? The PR writer for GMU certainly doesn't have a clue. Should we take that as saying something about GMU? I hope not.
1.2 / 5 (6) Jun 25, 2009
Assuming constant density, smaller dimensions = smaller mass.
5 / 5 (4) Jun 25, 2009
"For millions of years, dinosaurs have been considered the largest creatures ever to walk on land."

Who was around 1 million years ago to give it such consideration?
1.4 / 5 (10) Jun 25, 2009
If the authors of this study have not considered the possibility of a lower surface gravity during the Age of Dinosaurs,compared to current values, then I would question the validity of the study.
1 / 5 (1) Jun 26, 2009
But global warming is REAL!
1 / 5 (1) Jul 01, 2009
I heard that the dinosaurs that used to hang around Hollywood and Vine were a lot skinnier than most.
2 / 5 (4) Aug 11, 2009
Well the Hollywood dinosaurs have to fit into costumes so they blend into the human population. You might be amazed as to how many people in the entertainment industry are dinosaurs.

2 / 5 (4) Aug 11, 2009
Smaller dimensions, or lighter, i.e lower mass?

Like many computer problems that question shows the difficulty was between the monitor and chair. Sometimes I do it too.

when they used the equation to determine the weight of living animals such as a hippopotamus and an elephant and discovered that the equation greatly overestimated the weight of these animals.

Mass is the answer to your question. This is why I often read the article a second time before posting since I often skim over them the first time. Tend to miss important stuff that way.


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