The Therizinosaurus cheloniformis stands as one of the most perplexing creatures from the Late Cretaceous period, primarily due to its combination of enormous size and bizarre anatomy. This dinosaur was a hulking bipedal animal, estimated to have reached lengths of 30 to 33 feet and weighed between 3 and 5 tons. It possessed a long neck topped with a relatively small head, giving it an appearance unlike its predatory relatives. This unusual set of features establishes the Therizinosaurus as a fascinating biological puzzle.
The Great Claws and the Dietary Mystery
The most striking feature of the Therizinosaurus is the set of massive, scythe-like claws on its forelimbs, which created the initial confusion about its diet. These claws were among the longest of any known animal, with the largest specimen measuring up to 3.3 feet in length. The name Therizinosaurus itself translates to “scythe lizard,” a direct reference to these formidable appendages. When the first fossilized claws were discovered in 1948, scientists initially believed they belonged to a large, turtle-like reptile.
The visual evidence of such immense, hooked claws strongly suggests a formidable predator, similar to carnivorous theropods. However, this impression is highly misleading regarding its actual feeding habits. Biomechanical studies indicate the claws were surprisingly delicate and not structured to withstand the high impact forces required for stabbing or wrestling prey. Instead of a weapon, the claws were more likely specialized tools.
The Definitive Herbivorous Diet
Despite its lineage within the Theropoda group, which includes most carnivorous dinosaurs, the Therizinosaurus was definitively an herbivore. This conclusion is reached by analyzing the broader suite of its physical characteristics, which override the visual paradox of the claws. The dinosaur likely used its long, powerful arms and claws primarily for foraging, employing a “hook-and-pull” technique. This method involved grasping high branches and pulling the foliage down to its mouth for consumption.
Its diet consisted of soft plant matter, such as leaves, twigs, and fruits, rather than tough, fibrous vegetation. This feeding strategy is comparable to that of modern high browsers like giraffes or the extinct ground sloths. The claws may also have served secondary purposes, such as a visual display for mating rituals or a defensive posture to intimidate large predators like Tarbosaurus.
Anatomical Evidence for Plant Consumption
The scientific justification for the herbivorous diet lies in several specific anatomical features that are ill-suited for a predator.
Skull and Jaw Structure
One telling indicator is the structure of its head, which, based on related species, was small relative to its body size and likely ended in a beak. This small skull housed relatively weak jaw muscles, which are insufficient for gripping and tearing meat, but perfectly adequate for clipping soft plant material. The teeth of its close relatives are small and leaf-shaped, or lanceolate, designed for nipping off vegetation rather than tearing like a carnivore’s.
Torso and Pelvis
The overall body shape, indicated by the pelvis, suggests a wide, barrel-like torso necessary to house a large digestive tract. A greatly enlarged gut is a characteristic adaptation in large herbivores, as it provides the space required for fermentation chambers where microbes can break down tough plant cellulose. The Therizinosaurus also possessed a uniquely structured pelvis, with its hip bones pointing backward, a feature seen in “bird-hipped” plant-eaters, but unusual for its theropod lineage. The long neck, which was supported by powerful musculature, allowed the dinosaur to reach high-growing foliage, confirming its adaptation as a browsing herbivore. This collection of specialized features confirms a dramatic case of dietary reversal within a group of otherwise meat-eating dinosaurs.