Soft tissues are among the first components to perish during the fossilization process, in contrast to bones and teeth, which can last for hundreds of millions of years. However, scientists have previously discovered undamaged soft tissue in dinosaur bones. The most well-known instance occurred in 2005 when Mary Schweitzer of North Carolina State University discovered collagen strands in a Tyrannosaurus rex's petrified leg bone.

However, such finds are uncommon and have only previously been made with fossils that were incredibly well preserved. The latest discovery, which Imperial College London researchers announced this week in the journal Nature Communications, is especially remarkable because the fossils they looked at are, to put it mildly, in rather bad shape.

“It's really challenging to convince curators to let you take pieces of their fossils”, as Susannah Maidment, an Imperial paleontologist and one of the study's principal investigators, said in an interview with the Guardian. “The specimens we analyzed are poor quality, quite fragmentary, and not the kinds of fossils you would anticipate to include soft tissue.”

The fossils to which Maidment is alluding were discovered in Canada over a century ago and eventually found their way to the Natural History Museum in London. A claw from a carnivorous theropod (perhaps a Gorgosaurus), a toe bone that resembles a Triceratops, and several limb and ankle bones from a duck-billed dinosaur are among them. Scientists chipped microscopic bits off the fractured fossils in order to locate clean, uncontaminated surfaces of the bones to analyze. Using an electron microscope, Maidment's co-lead researcher Sergio Bertazzo examined the specimens and was astounded by what he discovered. Bertazzo is a materials scientist at Imperial College London.

“It looked like blood when I turned on the microscope and increased the magnification one morning.” Bertazzo described his examination of the theropod claw in his statement to the Guardian. After discovering what appeared to be red blood cells in two of the fossils, the researchers investigated the idea that the blood may have been contaminated historically, such as if a curator or collector had a cut while handling the item.

However, they were certain the blood was not human when they cut up one of the red blood cells and discovered what appeared to be a nucleus. Human red blood cells, like those of other mammals, are unique among vertebrates in that they do not include a cell nucleus.

However, it wasn't all. The scientists discovered bands of fibers while studying a cross-section of a preserved rib bone. Collagen, which serves as the primary structural protein in skin and other soft tissues, was discovered to contain the same amino acids in the fibers after they underwent testing. The materials the Imperial scientists discovered still need to be put through more tests to determine whether they are real red blood cells and collagen fibers, but if they are, the implications of the new discoveries are profound. Similar materials could be kept on any of the innumerable dinosaur bones housed in museums throughout the world if such poor fossils could contain soft tissue.

Soft tissue research could open up a whole new world of knowledge on the physiology, behavior, and evolution of dinosaurs. Such recent discoveries may shed light on long-standing questions regarding the links between various dinosaur species as well as the hotly contested issue of whether dinosaurs had warm or cold blood, or whether they were a combination of the two (like their living descendants, birds).

Finally, the latest discoveries suggest an intriguing possibility: Why couldn't dinosaur DNA, even in pieces, have persisted for 75 million years if collagen and red blood cells could? Could the genetic code be used to recreate the dinosaurs in the way of “Jurassic World”? Although Bertazzo acknowledges the prospect of discovering genetic information in historical specimens, he is dubious about its likelihood. “Even if you find DNA, it won't be complete, which is the problem. You might discover pieces, but to discover more than that? No one knows.”