For a long time, it was thought that only the hard bones and structures of dinosaurs could become preserved and fossilized for millions of years, as the soft tissue rotted away. Now, however, with better and more precise technology, paleontologists are slowly realizing that this isn’t always the case. From skin to blood cells, dinosaur fossils can actually preserve a whole range of soft tissues, if only you know where to look.
New research, published in the Journal of Proteome Research, has added blood vessels to the list of soft tissue that can be preserved in fossils. The specimen in question is from a hadrosaur, or “duck-billed” dinosaur, that lived around 80 million years ago in what is now Montana. While it had been suggested earlier that the structures found in the dinosaur's leg bone were blood vessels, there was some debate as to whether they actually represented fossilized blood vessels or were merely microbial contaminants. Now, the researchers claim to have settled it: They are indeed dinosaur in origin.
Blood vessels from the demineralized hadrosaur bone. M. Schweitzer/NC State University
“This study is the first direct analysis of blood vessels from an extinct organism, and provides us with an opportunity to understand what kinds of proteins and tissues can persist and how they change during fossilization,” explains Tim Cleland, who co-authored the study, in a statement. “This will provide new avenues for pursuing questions regarding the evolutionary relationships of extinct organisms, and will identify significant protein modifications and when they might have arisen in these lineages.”
The blood vessel-like structures were identified by demineralizing a piece of leg bone from the hadrosaur (Brachylophosaurus canadensis), which resulted in structures that were not only transparent, but also flexible. To test whether or not these were genuinely derived from blood vessels, or were actually the result of bacteria or fungi that had invaded the bone once the original structures had decomposed, the researchers turned to the modern descendants of dinosaurs: chickens and ostriches.
They took the leg bones from the modern birds and subjected them to the same demineralization process they conducted on the dinosaur bones, then used a technique called mass spectroscopy on the samples to determine the signatures of proteins from the structures that were left over. They compared these signatures to those from the dinosaur samples, and found that they both matched protein sequences found in blood vessels, confirming their origin. One of the protein signatures found was from myosin, which is usually found in the smooth muscle that surrounds blood vessels.
By knowing the signature of proteins from millions of years ago, it could open up new ways for scientists to study how they have changed between then and modern day, allowing a deeper understanding of how these animals were adapted to their environment.