The Ankylosaurus, a massive armored dinosaur of the Late Cretaceous period, is instantly recognizable by its heavy dermal armor and the formidable bony club at the end of its tail. This “fused lizard,” weighing up to four tons and stretching over 20 feet long, was built like a living tank, an adaptation primarily for defense against large predators like Tyrannosaurus rex. Despite its fearsome appearance, the Ankylosaurus was a dedicated herbivore, its entire anatomy geared toward processing immense quantities of plant matter.
The Definitive Diet
The diet of Ankylosaurus consisted almost exclusively of low-growing vegetation, making it a ground-level browser. Its wide muzzle and short stature restricted its feeding height to plants growing close to the ground. To sustain its massive body, the dinosaur needed to consume a large volume of food daily, estimated to be around 130 pounds, comparable to a modern elephant’s intake.
The primary sources of nutrition were soft, leafy plants, abundant ferns, and low-lying shrubs. The Ankylosaurus likely favored non-fibrous materials like pulpy fruits and cycads over tough, woody plants. This preference suggests a non-selective, bulk-feeding approach, where the dinosaur cropped large mouthfuls of whatever was available in its immediate vicinity.
Anatomical Evidence Supporting Herbivory
The physical structure of the Ankylosaurus skull provides clear evidence of its herbivorous lifestyle. The front of the jaws was covered by a broad, horny beak (rhamphotheca), adapted for efficiently clipping or cropping bundles of vegetation rather than precise biting. Behind this beak, the dinosaur possessed small, leaf-shaped, peg-like teeth.
These teeth lacked the complex grinding surfaces necessary for thorough mastication, functioning mainly to hold and process plants before swallowing. The jaw mechanics suggest a relatively low mechanical advantage, limiting the force of the bite and supporting the idea of feeding on softer plants. Further evidence is the massive width of its rib cage, which indicates an extremely large gut cavity required to break down vast quantities of fibrous plant material through fermentation.
Low-Lying Feeding Strategy
The daily life of Ankylosaurus was characterized by slow, deliberate movement as it grazed across its territory. Its wide muzzle facilitated a non-selective cropping habit, allowing it to sweep the ground and ingest large amounts of vegetation quickly. Since advanced chewing mechanisms were absent, the primary work of digestion occurred in the specialized gut.
The large gut cavity functioned as a fermentation vat, where microorganisms broke down cellulose and other plant fibers. This reliance on internal fermentation meant the Ankylosaurus spent less time chewing and more time foraging to meet its high caloric needs. Its low-slung body, heavy armor, and slow, grazing pace defined its ecological niche, allowing it to feed safely and continuously on the abundant ground cover.