Zuul

Zuul crurivastator was a heavily armored ankylosaurid dinosaur that roamed what is now Montana during the Late Cretaceous period, roughly 75 million years ago. Its species name, meaning "destroyer of shins," refers to the devastating tail club positioned at the perfect height to shatter the leg bones of attacking tyrannosaurs. This biological wrecking ball combined thick bony armor, rows of menacing spikes, and one of the most formidable defensive weapons in dinosaur history.

The holotype specimen, nicknamed "Zuul" after the demonic entity from the 1984 film Ghostbusters due to its fearsome horned skull, represents one of the most complete ankylosaurid fossils ever discovered in North America. Remarkably, the specimen preserved not only the complete skull and tail club, but also extensive soft tissue remains including skin impressions, keratin sheaths over the osteoderms, and the arrangement of armor in its original life position. This exceptional preservation has provided unprecedented insight into how ankylosaurs actually looked in life.

Discovered in the Judith River Formation and described in 2017 by Victoria Arbour and David Evans, Zuul has revolutionized our understanding of ankylosaurid anatomy and behavior. The specimen shows evidence of healed injuries on its flanks, possibly from combat with other Zuul individuals—suggesting these animals may have used their tail clubs not just for defense against predators, but also in battles with rivals over territory or mates.

As an herbivore, Zuul would have spent its days browsing on low-growing vegetation, its wide skull adapted for cropping plants while its fermentation-chamber gut processed tough plant material. Despite its formidable appearance, this was a peaceful plant-eater that relied on its impressive arsenal purely for defense—though any predator foolish enough to approach from behind would quickly learn why this dinosaur earned its fearsome name.