| Diet | Herbivore |
| Height | 1.2m |
| Length | 4m |
| Weight | 1.5 tonnes |
| Environment | Land |
| Era | Cretaceous |
| Period | Late Cretaceous |
| Type | Ankylosaur |
| Location | North America |
Hierosaurus was an ankylosaur that lived during the Late Cretaceous period, between 87 and 82 million years ago. Unlike many of its dinosaur contemporaries that roamed ancient forests and plains, Hierosaurus lived in a unique environment - near the shores of the Western Interior Sea that once covered much of central North America. Its fossils were discovered in marine chalk deposits in Kansas, suggesting this armoured herbivore lived close to ancient coastlines.
As an ankylosaur, Hierosaurus was a heavily armoured, plant-eating dinosaur that walked on four sturdy legs. It belonged to the nodosaurid group of ankylosaurs, which means it lacked the distinctive club-shaped tail weapon that other ankylosaurs possessed. Instead, Hierosaurus relied on its body armour and possibly shoulder spikes for protection against predators. Its low-slung body would have been covered in bony plates called osteoderms that formed a protective shell.
This dinosaur would have spent its days browsing on low-growing plants, using its beak-like mouth to crop vegetation. Its teeth were small and leaf-shaped, perfect for processing tough plant material. The coastal environment where Hierosaurus lived would have provided abundant ferns, cycads, and early flowering plants to sustain this herbivorous dinosaur.
Unfortunately, Hierosaurus is known from only fragmentary remains, including some armour plates and vertebrae. This makes it difficult for palaeontologists to determine its exact size and appearance, leading to its classification as a nomen dubium - a name of doubtful validity due to insufficient fossil evidence.
Hierosaurus possessed the typical nodosaurid body plan with heavy armour plating but no tail club. Its armour plates were likely arranged in rows across its back and sides, providing excellent protection from predators.
Hierosaurus likely lived in small groups near coastal areas, feeding on low-growing vegetation throughout the day. When threatened, it would have crouched down to protect its unarmoured belly whilst presenting its heavily armoured back to predators.
Hierosaurus was first described by Samuel Wendell Williston in 1898. The original fossils were discovered at Smoky Hill Chalk Member, Niobrara Formation, Kansas, USA.
