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What defensive structures did stegosaurs and ankylosaurs have?

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Illustration showing various dinosaur species drawn to scale and grouped by geologic era: Late Cretaceous, Early Cretaceous, Jurassic, and Triassic. Dinosaurs range from large species like Brachiosaurus and Tyrannosaurus to smaller ones like Velociraptor and Compsognathus, with a human silhouette included for size comparison. Measurement bars at the bottom indicate 1 meter and 3 feet for scale reference. — dinosaur A selection of dinosaurs grouped by the geologic interval in which they lived.

Stegosaurs and ankylosaurs were both heavily armored ornithischian dinosaurs that relied on specialized structures for defense.12

Stegosaurs

Stegosaurs are characterized by a double row of bony plates along their backs. While these plates may have served other functions, such as thermoregulation or display, the primary defensive weapons for many species were the pairs of long, pointed bony spikes located at the end of the tail.34

Ankylosaurs

Ankylosaurs, often called armored dinosaurs, possessed a more extensive defensive system. Their bodies were encased in a mosaic of thick, interlocking bony plates that protected their back and flanks. These were supplemented by:21
* Bony spikes: Rows of spikes often projected from the flanks.1
* Armored skull: The head was heavily protected by thick bone and spikes, with some species even developing bony coverings for their eyelids.12
* Tail club: Advanced ankylosaurs featured a massive, heavy club at the end of the tail, formed by fused vertebrae and bony plates, which they likely swung at predators.12