The Apatosaurus, one of the most recognized long-necked dinosaurs, was definitively a herbivore, meaning its diet consisted solely of plants. This massive animal belonged to the sauropod group, all of which were plant-eaters throughout their existence. The fossil record and anatomical features provide clear evidence that this giant was physically incapable of hunting or consuming meat.
Defining the Apatosaurus
The Apatosaurus was a member of the Sauropoda group, specifically classified within the Diplodocidae family, which includes other long-necked giants. This sauropod lived in what is now North America during the Late Jurassic period, approximately 152 to 151 million years ago. Its name, meaning “deceptive lizard,” was given because some of its initial fossil bones were confusingly similar to those of marine reptiles.
This dinosaur was among the largest land animals to ever live, reaching an average length of up to 75 feet and weighing between 20 and 41 tonnes. Its immense size and structure, characterized by a long neck, small head, and a massive, barrel-shaped body, were adaptations for consuming vast quantities of vegetation.
Anatomical Proof of Herbivory
The primary evidence for the Apatosaurus’s plant-based diet is found in the morphology of its skull and teeth. The dinosaur possessed a small, elongated skull relative to its body size, a feature not seen in large predators. Its jaws were lined with small, slender teeth that are described as peg-like or spatulate.
These teeth were not suited for grinding or chewing tough plant fiber, nor were they designed for tearing flesh like a carnivore’s serrated blades. Instead, the pencil-shaped teeth were used primarily for stripping foliage, effectively raking leaves and needles off branches. The dinosaur’s feeding strategy was bulk-feeding, where vegetation was stripped and swallowed whole or in large chunks, with minimal processing in the mouth.
Since the Apatosaurus did not chew its food, the digestive process relied heavily on a specialized gut and the use of gastroliths, or stomach stones. These polished stones were intentionally swallowed to remain in the stomach, where muscular contractions would use them to grind and break down the tough plant matter. The massive size of the Apatosaurus’s torso suggests the presence of an enormous gut cavity needed for the fermentation of cellulose, a process common in modern large herbivores.
The Jurassic Diet
The Apatosaurus lived in a landscape dominated by specific plant life. The primary sources of food were gymnosperms, including conifers like Araucaria, as well as ferns and cycads.
Due to its immense size and the low nutritional value of the Jurassic flora, the Apatosaurus had a massive caloric requirement, forcing it to eat nearly constantly. It would have used its long neck to browse on high vegetation, but also to sweep wide swaths of ground-level plants without having to move its body. Estimates suggest the Apatosaurus may have consumed a ton or more of plant material daily to fuel its metabolism.