About 75 million years ago, in what is now Alberta, Canada, a dinosaur called Euoplocephalus took its final breath. That exhalation, like every other, was fleeting and insubstantial, but eons later, scientists can still reconstruct the path it took out of the dinosaur’s head. And that path, it turns out, was extraordinarily convoluted.
Euoplocephalus was one of the ankylosaurs—a group of tank-like species covered in bony plates. Their skulls and backs were armored. Their eyelids were occasionally armored. Even the nasal passages inside their skulls were lined with bone, preserving these delicate structures, usually lost to time.
More than a century ago, paleontologists first noticed that those passages included a weirdly complicated series of chambers and tubes. They interpreted these as a set of sinuses that branched from a simple central channel—a slightly more elaborate version of the setup that exists inside your nose. But in 2008, Lawrence Witmer and Ryan Ridgely from Ohio University worked out what was really going on when they put the skulls of several ankylosaurs in a medical CT scanner.
The scans revealed the unusual structure of the creatures’ nasal passages—not sinuses forking off a central channel, but a single airway that repeatedly twists and turns, like roller-coaster tracks or a Krazy Straw. These passages are more complex than the airways of other backboned animals, and they’re remarkably long. The skull of Euoplocephalus “is the length of your arm from the wrist and elbow, but its nasal passage, if stretched out, would run from your shoulder to your fingertip,” says Witmer. “I remember standing up at a paleontology meeting, holding up my hands, and saying, ‘I don’t believe it, but this is what we got.’”