The name Ankylosaurus translates to “fused lizard,” fitting its massive, bony armor. This heavily built creature, weighing up to eight tons and reaching 26 feet long, lived during the very end of the Cretaceous Period (68 to 66 million years ago). Its most recognizable features were the extensive armor plating and the enormous, bony tail club. Despite its formidable appearance, Ankylosaurus was a dedicated herbivore whose body plan was adapted for defense while it foraged. Examining its anatomy and environment reveals the specifics of its menu and eating mechanics.
The Diet of a Low-Grazer
The sheer size and low-slung posture of Ankylosaurus restricted it to eating plants that grew close to the ground. This armored giant was a non-selective, low-level browser, consuming vegetation readily available within its reach, likely no higher than one meter off the ground. Its diet consisted primarily of low-growing, non-flowering plants abundant in the Late Cretaceous environment, such as ferns, cycads, and low shrubs. The specific types of flora consumed were fibrous and relatively low in nutritional value, requiring the animal to consume vast quantities to sustain its massive body mass.
Ankylosaurus needed to consume around 60 kilograms of vegetation daily, a volume comparable to that eaten by a modern elephant. This bulk forage requirement suggests the animal spent a significant portion of its day grazing. The broad muzzle was particularly suited for non-selective cropping, allowing it to sweep up large amounts of ground-level plants at once. Some evidence suggests the diet may have occasionally included pulpy fruits, offering a slightly higher-calorie option when available.
Anatomical Evidence Supporting Herbivory
The physical structure of the Ankylosaurus skull and digestive system provides strong evidence for its plant-based diet. The front of the dinosaur’s jaws was covered by a broad, toothless beak used to clip or snip vegetation. Behind the beak were small, leaf-shaped teeth. These simple, peg-like structures could process soft plant material but were not capable of the complex chewing required for tough fibers or meat.
The jaw structure of Ankylosaurus was relatively weak, limiting its ability to chew tough or woody plants into a fine pulp. Consequently, the dinosaur swallowed large pieces of un-chewed plant matter, necessitating a specialized digestive process. Scientists hypothesize that the massive, broad body housed a large gut or fermentation chamber. This internal structure relied on microbial fermentation to break down the tough cellulose and fibrous material that the simple teeth could not process.
Placing Ankylosaurus in the Cretaceous Ecosystem
Ankylosaurus lived in western North America, thriving in warm, lush habitats like floodplains and coastal areas. This massive herbivore played a unique role in its ecosystem by specializing in low-level browsing, differentiating its food source from high-browsing long-necked dinosaurs. Its preference for ground-level vegetation meant it was a major consumer of ferns and low shrubs, significantly shaping the plant life near the soil.
The heavy armor and tail club provided a necessary defense against apex predators, most notably Tyrannosaurus rex, which co-existed with Ankylosaurus. Its heavily armored dorsal side and low profile made it nearly impossible for a predator to flip the animal over to attack its vulnerable underside. This reliance on defensive adaptations allowed it to survive in an environment shared with powerful carnivores.