In 2013, London's Natural History Museum acquired a rare Stegosaurus skeleton. What made it so special is that only a few bones were missing -- the left forelimb, part of the tail and a few other small bones -- making it the most complete skeleton of a single Stegosaurus ever found, and an exceptional one at that, opening up broad new avenues for research.
"Although Stegosaurus has been known about for more than 130 years, not much is known about its biology. Because the new skeleton is almost complete, and three-dimensional, we can do a lot of things that have not been possible until now, such as looking at how the leg muscles work or how the skull functions during biting," explained Natural History Museum dinosaur researcher Professor Paul Barrett.
"Thanks to this fossil, we can begin to uncover the secrets behind the evolution and behaviour of this iconic but poorly understood dinosaur species."
The bones, however, are extremely valuable, and need to be handled with care. Excavation of the skeleton from its grave in Red Canyon Ranch, Wyoming took 18 months, from discovery in 2003 to its final uncovering in 2005. Performing experiments that could cause wear and tear on the fragile bones is not a good idea.
For this reason, the team has digitised the skeleton, which measures three metres tall and six metres long, creating a 3D model from images of the actual bones.
"The technique I use to create a 3D computer model of an animal's skeleton is known as photogrammetry, which involves taking dozens of photographs of each bone from every possible angle. I apply a matching algorithm to find areas where the photographs overlap and use this to generate a 3D model of each bone. I can then build a virtual model of the entire skeleton," explained the Museum's Dr Charlotte Brassey.
"The big advantage of photogrammetry is that it doesn't require much equipment, just a digital camera and a tripod, and the software is freely available. Thanks to this technique, we can generate 3D models of fossils without expensive scanning equipment. We can even make reasonable 3D models in the field using just a smartphone."
The resultant 3D model can then be used to make calculations and share information about the skeleton. For example, the model can be sent to other museums that have partial Stegosaurus skeletons for comparison, and they can use it to make their own observations.
Dr Brassey used it to calculate the mass, and from there the weight of the Stegosaurus in question -- a number she is unable to reveal at this time, since it is an important part of a paper soon to be published in a peer review journal. The weight of the Stegosaurus, though, is an important thing to know, since it can help calculate how fast it can move, how much it needs to eat and how it interacts with other species.
What she found was that the weight she calculated was a very different number from estimates of dinosaur weight based solely on the leg bones. This matters a great deal: the weight of many specimens is calculated solely on the leg bones, since the leg bones are often all that researchers have available. This research highlights the importance of using a complete skeleton, and may be able to offer insight into how to calculate dinosaur weight in the future.
You can read more about this extraordinary skeleton on the National History Museum website.