The Therizinosaurus, a dinosaur that roamed Earth around 70 million years ago during the Late Cretaceous period, presents a striking and often perplexing image. Its most notable feature, massive claws, initially led to significant misconceptions about its lifestyle. These imposing appendages, combined with its large size—up to 10 meters (33 feet) long and weighing over 5 tons—made many early researchers assume it was a fearsome predator. However, this “scythe lizard,” as its name translates, holds a surprising secret regarding its diet, challenging initial assumptions based on its formidable appearance.
The Unexpected Herbivore
Despite its intimidating claws and classification within the theropod group, which primarily consists of carnivorous dinosaurs, the Therizinosaurus was a dedicated herbivore. Its diet likely included leaves, twigs, and possibly fruits and seeds from the abundant vegetation of the Late Cretaceous period.
During the Late Cretaceous, the environment in what is now the Gobi Desert of Mongolia, where Therizinosaurus fossils have been found, featured extensive woodlands and forests. These lush habitats provided a rich source of plant life, including conifers like Glyptostrobus and Metasequoia, as well as diverse flowering plants such as magnolias, sassafras, and willows. The Therizinosaurus would have browsed on this varied flora, consuming tough fibrous vegetation to sustain its large body.
Uncovering Its Diet
Paleontologists determined the herbivorous nature of Therizinosaurus through careful examination of fossil evidence, despite the lack of a complete skull. The dentition of its relatives within the therizinosaur group, like Erlikosaurus and Segnosaurus, provides key clues. These related species possessed leaf-shaped teeth with serrated edges, designed for processing plant material rather than tearing flesh.
The structure of the Therizinosaurus jaw, inferred from related species, also indicates an adaptation for grinding and shearing vegetation. Unlike carnivores with sharp, pointed teeth and powerful jaws for gripping prey, therizinosaurs generally had a small head and a beak-like mouth. The absence of features typical of predators, such as sharp, recurved teeth, further supports its plant-eating lifestyle. Gastroliths, or stomach stones, found in other large herbivores, may also have aided digestion.
Specialized Features for Foraging
The unique anatomical features of the Therizinosaurus were well-suited for its herbivorous diet. Its famously long manual claws, which could reach up to 1 meter (3.3 feet), were not primarily for attacking prey. Instead, these robust claws were likely used in a “hook-and-pull” fashion to bring branches and foliage within reach, allowing the dinosaur to strip leaves or pull down vegetation from trees. This adaptation allowed it to access a wider range of plant food, similar to how modern ground sloths or large mammals forage.
Therizinosaurus also possessed a long neck, which would have enabled it to reach higher foliage, making it a high browser. The front of its mouth likely featured a rhamphotheca, a horny, beak-like structure, for cropping vegetation efficiently. Its broad body structure suggests a large gut cavity, necessary for housing an extensive digestive system capable of fermenting and breaking down tough plant fibers. This combination of specialized traits allowed the Therizinosaurus to thrive as a unique herbivore in its ancient ecosystem.