The museum, which is a part of Montana State University, has a laboratory that specializes in cellular and molecular paleontology (the study of prehistoric life through fossil remains).
The study authors also looked at several other dinosaur fossils to see whether there was something unique about this particular T. rex fossil.
"There's nothing unique about the specimen other than the fact that it's the first that's been examined really well," Horner concluded. Other dinosaurs, in other words, are probably similarly preserved.
Schweitzer's background is in biology, and she performed a number of tests on the fossils that are common medical practices today.
The paleontologist and her colleagues removed mineral fragments from the interior of the femur by soaking it in a weak acid. The fossil dissolved, exposing a flexible, stretchy material and transparent vessels.
The vessels resemble blood vessels, cells, and the protein matrix that bodies generate when bones are being formed.
"Bone is living tissue, is very active tissue, and has its own metabolism and has to have a very good blood supply," Schweitzer said.
"So bone is infiltrated with lots and lots of blood vessels in its basic structure. When bone is formed, it's formed by cells that are specific for bone, that secrete proteins like collagen and form a matrix."
Further chemical analysis might enable the scientists to answer long-standing questions about the physiology of dinosaurs. For instance, were they warm-blooded, cold-blooded, or somewhere in between?
If protein sequences can be identified, they can be compared to those of living animals. This might allow a better understanding of how different groups of animals are related.
The find may potentially change field practices, perhaps by encouraging more scientists to reserve parts of fossils for cellular and molecular testing.
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