Unlike bones and teeth, which can survive for hundreds of millions of years, soft tissues are among the first materials to disappear during the fossilization process. Even so, scientists have found intact soft tissue in dinosaur bones before. The most famous case dates to 2005, when Mary Schweitzer of North Carolina State University found collagen fibers in the fossilized leg bone of a Tyrannosaurus rex. But such discoveries are rare, and have previously occurred only with extremely well preserved fossils. The most extraordinary thing about the new find, which scientists from Imperial College London reported this week in the journal Nature Communications, is that the fossils they examined are of relatively poor condition (to put it kindly).
As Susannah Maidment, an Imperial paleontologist and one of the lead researchers on the new study, told the Guardian: “It’s really difficult to get curators to allow you to snap bits off their fossils. The ones we tested are crap, very fragmentary, and they are not the sorts of fossils you’d expect to have soft tissue.”
The fossils Maidment is referring to were uncovered in Canada a century ago, and eventually ended up in London’s Natural History Museum. They include a claw from a carnivorous theropod (possibly a Gorgosaurus), a toe bone resembling that of a Triceratops and several limb and ankle bones of a duck-billed dinosaur. In order to find fresh, uncontaminated surfaces of the bones to examine, scientists broke tiny pieces off the fragmented fossils. When Sergio Bertazzo, a materials scientist at Imperial and Maidment’s co-lead researcher on the study, looked at the specimens using an electron microscope, he was shocked at what he saw.
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“One morning, I turned on the microscope, increased the magnification, and thought ‘wait – that looks like blood!’” Bertazzo told the Guardian, recounting his examination of the theropod claw. After finding what looked like red blood cells in two of the fossils, the researchers explored the possibility that the blood might be the result of historical contamination; for example, a curator or collector might have had a cut when they handled the specimen. But when they sliced through one of the red blood cells and saw what looked like a nucleus, they felt confident the blood was not human. Red blood cells of humans, like other mammals, are unusual among vertebrates because they lack a cell nucleus.
And that wasn’t all. While examining a cross-section of a fossilized rib bone, the researchers spotted bands of fibers. When tested, the fibers were found to contain the same amino acids that make up collagen, the main structural protein found in skin and other soft tissues. More tests remain to confirm that the materials the Imperial scientists found are in fact genuine red blood cells and collagen fibers, but if confirmed, the implications of the new findings are huge. If such sub-par fossils could contain soft tissue, similar materials could be preserved on any of the numerous dinosaur bones housed in museums around the world.
By studying soft tissue material, scientists could gain access to a whole new realm of information about dinosaur evolution, physiology and behavior. Such new information might provide clues to longstanding mysteries about the relationships between different species of dinosaurs, as well as the much-debated question of whether dinosaurs were cold-blooded, warm-blooded (like their modern-day descendants, birds) or somewhere in between.
Finally, the new findings raise a tantalizing possibility: If collagen and red blood cells can survive for 75 million years, couldn’t dinosaur DNA—even in fragments—also have survived? Could scientists use that genetic code to resurrect the dinosaurs, “Jurassic World”-style? Bertazzo admits that finding genetic information in ancient specimens is a possibility, but is cautious about its likelihood. “The problem with DNA is that even if you find it, it won’t be intact. It’s possible you could find fragments, but to find more than that? Who knows?”