Scientists Calculate the Body Mass of a Stegosaurus

A team of scientists based at the Natural History Museum (London), have calculated the weight of “Sophie”, the beautifully preserved and nearly complete Stegosaurus fossil skeleton that has been on display at the museum since last November.  This is the first set of data to be released about this, most iconic dinosaur, famous for its tiny brain and those remarkable plates running along its back.  The research team headed by Dr. Paul Barrett hope to release more findings throughout the year.  The weight of the 5.6 metre long animal, has been calculated at 1.6 Tonnes, not a bad size for a dinosaur that was not yet fully grown when she died.

“Sophie” The Stegosaurus Weighs 1,600 Kilogrammes

The preserved skeleton of "Sophie" the Stegosaurus.

The preserved skeleton of “Sophie” the Stegosaurus.

Picture Credit: Natural History Museum (London)

Team members at Everything Dinosaur predicted at the beginning of the year that much more information would be known about Stegosaurs over the course of 2015 thanks to the palaeontologists and other scientists based at the museum.  It was one of the company’s “palaeontology predictions” for this year.  Ironically, despite this dinosaur’s popularity (it came in at number four in Everything Dinosaur’s most popular prehistoric animals survey), very little academic work has been carried out on Stegosaurus for more than eighty years.

Palaeontologists like Dr. Charlotte Brassey, the lead author of a paper about “Sophie” and her body weight are changing all that, the doctor and her colleagues will be embarking on a series of research projects aimed at helping us to learn more about this Late Jurassic herbivore.  The first research paper has just been published in the journal “Biology Letters”.  Knowing the body mass of an animal is very important as it allows researchers to answer a lot more questions once this data has been established.

Dr. Brassey explained:

“If we want to estimate how fast an animal runs, you need body mass; if you want to say something about their metabolism, you need to know their body mass.  So, yes, we’re really glad that we’ve been able to get hold of this very early on, and now what I’m looking to do is begin to strap muscles on to our computer models so that we can get her walking to say something about locomotion.”

The specimen, originally from Wyoming, consists of over 360 individual bones, about 80% of this material is actually fossil, the rest of the skeleton has been built up using casts of other specimens and reconstructions of missing pieces.  Prior to the skeleton being put on display, each one of these objects was scanned and mapped onto a computer programme using a Computer Aided Design (CAD) package.  It was from this modelling data that an estimated body mass of 1.6 Tonnes was calculated.  Although not fully grown, “Sophie” still weighed more than the fifteen players in England’s rugby team combined.

More traditional methods of calculating body weight involve measuring the circumference of the femur (thigh bone) and the humerus (upper arm bone).  The ratios between these two bones and body weight in extant animals is well established, the bigger the circumference the heavier the animal is the simple rule.  The new CAD modelling technique agrees with the figure for body mass calculated using the measurements from the major limb bones.  The scientists are confident that their data is correct and “Sophie” weighed in at around 1.6 Tonnes.  This suggests that a fully grown Stegosaurus stenops probably weighed more than three thousand kilogrammes.

A Fully Grown Stegosaurus Probably Weighed More Than Three Tonnes

A remarkable dinosaur.

A remarkable dinosaur.

Picture Credit: Everything Dinosaur

We look forward to learning more about Stegosaurs, one question that does need answering for example, is this, should we refer to this Stegosaurus as “Sophie”?  Will the scientists be able to confirm that this individual was a female?

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