Pulling apart limbs, sawing through ribs and separating skull bones are activities usually associated with surgeons rather than museum staff. However, that is exactly what is going on at the Smithsonian's National Museum of Natural History in Washington DC, USA. Renovations to the museum's dinosaur hall, which started recently, have necessitated the dismantling and removal of its collection of dinosaur and extinct mammal skeletons, some of which weigh as much as five tons.

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One particular specimen which curator Matthew Carrano can't wait to get hold of is a meat-eating Jurassic dinosaur called Allosaurus, which has been on display for 30 years. 'Scientifically, this particular Allosaurus is well known, he explains, because 'for a long time, it was one of the only Allosaurus specimens that represented a single individual animal,'

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The Smithsonian's five-meter-long Allosaurus, however, is definitely one, unique individual. So once the crystallized glue holding it together is removed, researchers and conservators can get a better sense of how the creature's joints actually fitted together in life.

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Another modification the museum plans to make to its Allosaurus is removing a couple of centimeters from its tail, which is not original fossil but casts of vertebrae. 'The tail on the Smithsonian's specimen is too long, says Peter May, owner and president of the company in charge of dismantling, conserving, and remounting the 58 specimens in the museum's

dinosaur hall. He explains that the skeleton on display has over 50 vertebrae, when it should have something closer to 45.

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Slicing a thin cross-section out of a leg or rib bone can help with that. By placing a slice under a microscope, researchers will be able to count growth rings on the bone, the number of which would have increased throughout the creature's life, very much like the rings on a cross-section of a tree trunk.

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One example which Carrano wishes to investigate further is an apparent blow to the Allosaurus's left side. The shoulder blade looks like it has healed improperly, he explains. If the damaged shoulder blade can be fitted together with the ribs which are held in storage, paleontologists might be able to determine the severity and cause of the damage.

Finally, Carrano hopes to be able to compare the Allosaurus with another dinosaur in the collection called Labrosaurus. Labrosaurus is known only from a single bone - a lower jaw with a distortion which is believed to have been caused by disease or injury. "The two front teeth are missing and there's an abscess there, Carrano explains.

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But in order to confirm their suspicion, Carrano and his colleagues will have to wait a while. A lot of what we hope to learn won't be accessible to us until the exhibits have been taken down and we can have a good look at them, he says. So he won't be able to get his hands on the Allosaurus quite yet.

A Dismantling the Allosaurus and removing the plaster and glue covering it can also reveal whether the animal suffered any injuries when alive.

B The Smithsonian's team should be able to take it apart in large chunks in a single day, but even once they've dismantled it they'll still have hours of work ahead of them, breaking the skeleton down further into individual bones and cleaning them.

C These endeavors will modernize a space which has never seen a major overhaul. It will also give researchers a chance to make detailed studies of the exhibits - some of which haven't been touched in decades.

D There are also plans to slim it down a little. When the museum first displayed the Allosaurus, preparators decided to use plaster casts of the ribs instead of the actual specimens, which resulted in a heavier-looking skeleton. Curators hope that the final, remounted skeleton will more closely resemble the dinosaur's natural shape.

E However, this dinosaur, previously classified as a separate species is now thought to be a type of Allosaurus. Both of the specimens come from the same quarry, and what's more the Allosaurus is missing the exact same bone, so it's entirely possible that it actually belongs to the Smithsonian Allosaurus.

F In addition to correcting mistakes such as this, made when the specimens were first displayed, Carrano would also like to determine the age of the Allosaurus.

G There are Allosaurus skeletons in museum collections across the world, but most consist of bones from a number of different examples of the species. This has made it difficult for scientists to work out how the entire skeleton fits together.