Tearing apart limbs, sawing through ribs, and separating skull bones are activities usually relegated to summer slasher movies, not the Smithsonian's National Museum of Natural History. However, renovations to the museum's dinosaur hall—which started this spring—necessitate the removal of dinosaur and extinct mammal skeletons that can weigh nearly five tons.
The renovations will modernize a hall that has never seen a major overhaul. They will also give researchers a chance to study the specimens on display—some of which haven't been touched in decades—in more detail.
Only by dismantling the skeletons and removing the plaster and glue covering the actual fossils can paleontologists answer questions such as the specimens' age, how their bones articulate, and whether the animals suffered injuries while alive.
Matthew Carrano, curator of dinosauria at the Smithsonian's National Museum of Natural History in Washington, D.C., can't wait to get his hands on a meat-eating Jurassic dinosaur called Allosaurus that has been on display for 30 years. "Scientifically, it's well known," he says, because "for a long time, it was one of the only Allosaurus specimens that represented a single individual."
All in One
There are a lot of Allosaurus specimens out there, Carrano said, but they consist of bones from many different individuals. It has been difficult for scientists to figure out how an Allosaurus skeleton fits together, because often the limbs are cobbled together from several animals.
The bones in the Smithsonian's 17-foot-long (5 meters) Allosaurus come from one individual. So once the crystallized glue holding the skeleton together is removed, researchers and conservators can get a better sense of how the joints articulate.
Carrano would also like to determine this particular individual's age. Slicing a thin cross-section out of a leg or rib bone can help with that. Placing that slice under a microscope, researchers will be able to count growth rings on the bone, very much like counting tree rings.
There's also evidence that this particular Allosaurus suffered a major injury to its left side. In preparation for the Allosaurus overhaul, researchers pulled out some ribs and a shoulder blade that have been sitting in storage and saw something interesting.
"The left shoulder blade looked like it was broken and then healed improperly," Carrano said. If paleontologists can fit the wonky shoulder blade together with the ribs, they might be able to tell the severity of the injury.
"It looked like [the Allosaurus] was whacked with a boulder or a sauropod tail," said Steve Jabo, a fossil preparator at the museum.
There are also plans to slim down their specimen. "Our Allosaurus has more of a barrel chest, and we need to make it a little [slimmer]," Jabo said.
When the museum first displayed the Allosaurus 30 years ago, researchers and preparators decided to use casts of the ribs instead of the actual specimens. Modifications to the rib shapes resulted in a heftier-looking finished product. Jabo says the final, remounted skeleton will look much more natural.
Researchers also plan to lop off a couple of inches from the Allosaurus's tail, which is not original fossil but made of casts of vertebrae. "The tail that's on that specimen is a little bit too big," said Peter May, owner and president of Research Casting International (RCI), a Canada-based company that is handling the dismantling, conservation, and remounting of 58 specimens in the museum's dinosaur hall.
"It's got over 50 vertebrae," May said, when it should have something closer to 45.
Finally, Carrano hopes to be able to compare the Allosaurus with another dinosaur in the collections called Labrosaurus. Labrosaurus is known only from a single bone, Carrano said. The bone is half of a lower jaw with a puffy front end. "It's [the result of] some sort of disease or injury where the two front teeth are missing and there's an abscess there," Carrano said.
However, Labrosaurus is now thought to be a type of Allosaurus, and both of the Smithsonian specimens come from the same quarry. Plus, the Allosaurus is missing the exact bone that's currently labeled Labrosaurus. "So it's entirely possible that this bone belongs to our [Allosaurus]," Carrano said.
"Frankly, a lot of the stuff we'll learn from these things won't happen until they come down and we have a good look at it," Carrano said. May and his crew were able to take the Allosaurus apart in big chunks in one day, but they still have hours ahead of them in the lab, where they'll break the skeleton down further into individual bones and clean them.
So Carrano and Jabo will have to wait.
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