Dinosaur fossils may have more to share with us than originally thought. By analyzing poorly preserved dinosaur bone fragments, scientists have found structures that closely resemble red blood cells and collagen fibers, proteins found in various types of tissues. The finding is exciting because it contradicts a widely held belief that only exceptionally well-preserved fossils harbor soft tissues. And the fact that 75 million-year-old fossils hold these kinds of cells means that we may find similar tissues in other not-so-well-preserved bone fragments — a finding that could drastically increase our knowledge of dinosaur biology, behavior, and evolution.

"We were not expecting to find what we found at all."

"We have several indications that the structures we found are consistent with red blood cells and collagen," explains Sergio Bertazzo, a physical chemist at Imperial College London and co-author of the study published in Nature Communications today. "We were not expecting to find what we found at all. So for us, every single discovery was quite exciting."

Scanning electron micrographs of samples extracted from ribs of an indeterminate dinosaur displaying mineralized fibres. Credit: Sergio Bertazzo

They compared the red blood cells to emu blood cells

In the study, researchers analyzed eight fossil fragments from two major dinosaur types, Ornithischia and Saurischia. To do this, they used a microscope called a "focused ion beam," which is equipped with a beam of atoms that can make tiny, nanometric cuts into a bone sample. The microscope also had a robotic arm with a micro needle that could be used to pick up and move things inside the microscope, Bertazzo explains."So, [by] combining the beam and the needle, we could cut small bits of the fossils and perform an analysis to check for any fragment of amino acids" — protein building blocks.

Thanks to this technique, the researchers were able to identify tiny structures that are probably red blood cells and collagen fibers belonging to the dinosaurs — something they never expected to find. The researchers confirmed the finding by comparing the red blood cell-like structures in the dinosaur bones to emu blood cells; birds and dinosaurs are distant relatives after all.

If other researchers can find similar results, scientists might be able to use these collagen structures to better understand relationships between different species. And because red blood cell size is known to correlate with metabolic rate, it's possible that these organic structures could help scientists find out more about how dinosaurs evolved in warm-blooded creatures.

Before this, the oldest un-degraded collagen was 4 million years old

This isn't the first such discovery; researchers have been able to find soft tissues like this in other fossils. What sets this study apart is the fact that the researchers were able to find these materials despite the fact that the fossils weren't exceptionally well preserved. And before this finding, the researchers note in the study, the oldest un-degraded collagen ever recorded was about 4 million years old.

There's one important limitation that's worth noting, however. It's possible that the red blood cells don't belong to the dinosaurs at all, Bertazzo says; contamination from other animals can't be ruled out. "Even if it is quite unlikely that someone or some bird cut themselves and bled on the fossil at any point in time and right on the spot we took the smaller bit off, this is always a possibility."

Credit: Sergio Bertazzo

And being able to identify structures like red blood cells and collagen in "unexceptional" fossils isn't going to lead to dinosaur de-extinctions — at least not any time soon. "At the moment we have no evidence for any DNA," says Susie Maidment, a paleontologist at Imperial College London and a co-author of the study. DNA is much smaller than collagen fibers and red blood cells, which means that it degrades more easily. "However, who knows what we might find in the future," she says.

"Unlikely that someone or some bird cut themselves and bled on the fossil."

Now that the study has been published, the scientists want to understand this type of preservation better. "How far back in time does it extend? Is it restricted to a particular type of burial environment?" Maidment asks. They also hope to find out how this type of preservation occurs.

The discovery could have a big impact on fossilization science. "Before this discovery, as a palaeontologist, I ‘knew’ that it was not possible for soft tissues to be preserved over geologic timescales, except in exceptionally rare circumstances," Maidment explains. "What is most exciting for me is the potential this opens up: if we are able to find these tissues in other specimens, and replicate the results, it indicates this type of preservation might even be the ‘norm.'"