Ankylosaurids

Ankylosaurids are a family of armored herbivorous dinosaurs within the larger clade Ankylosauria. They are the club-tailed, more derived members of the group, distinguished from nodosaurids primarily by the presence of a large tail club and by skull and armor features. They were quadrupedal, low-slung animals with extensive dermal armor.

They were built for defense, with the body covered in osteoderms embedded in the skin and arranged in rows over the back and sides. The tail bore a large, bony club formed by thickened terminal vertebrae and expanded osteoderms. The skull was boxy, with a beak and tooth plates arranged in dental batteries; the cheeks were heavily armored.

They lived during the Cretaceous period, roughly 125 to 66 million years ago, with fossils found in North America, Europe, and Asia. Ankylosaurids were herbivores that fed on low-lying vegetation. Their extensive armor and tail club provided defense against predators such as tyrannosaurs. The tail club may have been used in defense, deterrence, or display, and some evidence suggests possible intraspecific combat.

Notable members include Ankylosaurus magniventris from North America; Euoplocephalus, Pinacosaurus, Saichania, and Tarchia from Asia; and others in Europe and North America. Within Ankylosauria, ankylosaurids constitute the family characterized by the tail club, as opposed to nodosaurids, which lack such a feature.