The world's most complete Stegosaurus skeleton was unveiled at England's Natural History Museum on Thursday.

The 2.9-metre tall and 5.6-metre long skeleton is more than 90 per cent complete. Scientists are only missing the dinosaur's left arm and the base of its tail.

Adult Stegosaurus can be up to nine metres long, which leads scientists to believe this is neither an adult nor a baby dinosaur. But they aren't able to determine the dinosaur's exact age.

Stegosaurus Natural History Museum

Researchers at the museum used 3D scanning techniques to estimate what Sophie would have weighed while alive. The nearly-complete skeleton will likely offer insight into the many remaining mysteries of Stegosaurus biology. (Paul Hackett/Reuters)

Finding such a complete skeleton is exceptional and an amazing find, said Paul Barrett of the museum's earth sciences department in a question-and-answer piece posted on the museum's website.

The skeleton was discovered at Red Canyon Ranch in Wyoming in 2003. Paleontologists spent 18 months digging out the bones.

The museum acquired the skeleton 10 years later, and researchers have been working on it since the bones arrived in December 2013.

Scientists are using data from measurements, photographs and scans of the skeleton to better understand the dinosaur's evolution and behaviour. Although scientists have been aware of the Stegosaurus for more than 130 years, they lack in-depth knowledge about its biology.

Stegosaurus Natural History Museum

The 150-million-year-old Stegosaurus stenops is the first complete dinosaur skeleton to go on display at the Natural History Museum in nearly 100 years. (Paul Hackett/Reuters)

"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," said Barrett.

He is most interested in how the Stegosaurus, which was a herbivore, ate, saying its tiny teeth "look like they would be pretty useless for chewing."

He's also excited to find out the dinosaur's weight, which could lead to other interesting discoveries, like how much it needed to eat.

The Stegosaurus lived during the late Jurassic period between 144 and 156 million years ago in the U.S. Although it was large and slow, its powerful spiked tail helped it fight off predators.

The Stegosaurus will be on permanent public display at the London museum.

See how the Stegosaurus was assembled in the museum