Was Stegosaurus’ spiky tail was simply ornamental or used for self-defense? Recent evidence seems to point to the quadruped’s ability to fend off predators with its formidable spiny weapon. Among known Stegosaurus fossils, roughly 10 percent have damaged tail spikes that started to heal and regrow while they were still alive, indicating that their tails often sustained injuries, potentially in self-defense.
A bone injury found on an Allosaurus fossil matches the size and scale of a Stegosaurus tail spike, and one study suggests that a piece of the Stegosaurus’ bone remained lodged in the Allosaurus’ vertebra. Fun fact: Many paleontologists informally refer to the dinosaur tail spikes as “thagomizer,” a term originally coined as a joke, for a Far Side cartoon.