Therizinosaurus is a genus of very large theropod dinosaurs. Therizinosaurus comprises the single species T. cheloniformis, which lived in the late Cretaceous Period (early Maastrichtian stage, around 70 million years ago), and was one of the last and largest representatives of its unique group, the Therizinosauria. Fossils of this species were first discovered in Mongolia and were originally thought to belong to a turtle-like reptile (hence the species name, T. cheloniformis – "turtle-formed"). It is known only from a few bones, including gigantic hand claws, from which it gets its name.
Though the fossil remains of Therizinosaurus are incomplete, inferences can be made about their physical characteristics based on related therizinosaurids. Like other members of their family, Therizinosaurus probably had small skulls atop long necks, with bipedal gaits and heavy, deep, broad bodies (as evidenced by the wide pelvis of other therizinosaurids). Their forelimbs may have reached lengths of up to 2.5 metres (8.2 feet) or even 3.5 metres (11.5 feet) in the largest known specimen. Their hindlimbs ended in four weight-bearing toes, unlike other theropod groups, in which the first toe was reduced to a dewclaw. In 2010 Gregory S. Paul estimated the maximum size of Therizinosaurus at 10 metres (33 ft) in length and five tones in weight.
The most distinctive feature of Therizinosaurus was the presence of gigantic claws on each of the three digits of their front limbs. These were common among Therizinosaurus but especially large in Therizinosaurus, and while the largest claw specimens are incomplete, they probably reached 0.7–1 metres (2.3–3.3 ft) in length. The claws are the longest known from any animal. The claws were relatively straight, only gradually tapering into a point, as well as extremely narrow and transversely flattened.
The feeding habits of Therizinosaurus are unknown since no skull material has ever been found that could indicate their diet. However, like other Therizinosaurus, they were most likely herbivorous.
This specimen is a reconstruction of a front hand claw and nail sheath which begs the question; what did Therizinosaurus do with such huge claws.
35 inches long
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