The leg bones of a 30-foot-long duck-billed dinosaur found in Montana have been hiding an exciting secret for millions of years: they still contain blood vessels. 

A team of researchers led by molecular paleontologist Tim Cleland of the University of Texas at Austin reports in the Journal of Proteome Research that a piece of leg bone from a Brachylophosaurus canadensis, dating back 80 million years, contains the hadrosaur’s blood vessels. After demineralizing the bone (a process which removes minerals like calciumduring his work as a grad student at North Carolina State University, Cleland found proteins associated with the walls of blood vessels. 

But first, he had to prove that these tissues belonged to the dinosaur, and weren’t some kind of contaminant not original to the animal. He and his team used modern relatives of the dinosaurs, like chickens and ostriches, comparing the structures found within their demineralized bones to those found in the hadrosaur, and matching the peptide sequences in the prehistoric blood vessels. 

Scientists have recently found a number of soft tissue samples in ancient fossils, from 75-million-year-old blood cells to 161-million-year-old poop. Soft tissues like blood vessels are especially valuable to researchers because, unlike hardier body parts such as bones, it’s rare for those delicate tissues to withstand the ravages of time. 

"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," Cleland explains in a press release