Researchers at Imperial College London and the British Natural History Museum have used a variety of methods to calculate the body mass of a 150 million year old Stegosaurus (Stegosaurus stenops) specimen nicknamed Sophie.

According to the team, the dinosaur would have weighted about the same as a small rhino or roughly 3500 pounds.

“These findings identify just how important exceptionally complete specimens like this are for scientific research and collections. Now we know the weight, we can start to find out more about its metabolism, feeding requirements and the growth rates of Stegosaurus. We can also use the same techniques on other complete fossils to find out much more about the wider ecology of dinosaurs,” said professor Paul Barrett, lead dinosaur researcher at the Natural History Museum in a statement.

The research was conducted, not using the specimen itself but a 3D digital model of the animal according to Dr Charlotte Brassey. Brassey is a palaeontologist from the Museum and lead author of the study which is published in Biology Letters.

“Because this incredible specimen is so complete, we have been able to create a 3D digital model of the whole fossil and each of its 360 bones, which we can research in excellent detail without using any of the original bones. We also took the skeleton’s leg bone circumference and compared it to a modern animal of similar size, and came up with matching estimates for the dinosaur’s weight,” she said.

When the two different methods of analysis were compared, the results were roughly the same. This gave the researchers a pretty good indication that they were in the right ballpark. Had the two results disagreed with one another, it would have meant that they were missing something or that the methods themselves had failed.

“Calculating body mass in animals that have been dead for many millions of years is no easy task, and there are several different ways to do it. Often different methods come up with very different results. Our study is the first to attempt different methods on the same animal, and has highlighted how and why different body mass estimation methods come up with different results. The age of the animal when it died is very important,” said Dr Susannah Maidment, a researcher at Imperial College London.

After Sophie arrived at the museum and before she went on display in 2014, researchers conducted a detailed analysis of the remains. This included 3D modeling of the entire skeleton by scanning, photographing and measuring each of her 360 bones. In addition to this study, a number of future studies are being planned using the 3D analysis to study the habits and lifestyle of Stegosaurus.

Stegosaurus which means “roof lizard” or “covered lizard” is best known for the bony plates which ran along its back. The large herbivorous animals lived about 150 million years ago and appear to have been widely distributed in the Northern Hemisphere. Specimens have been found across North America and in Portugal which means that they lived in Europe as well.