Therizinosaurus Maleev 1954

Therizinosaurus is Greek for 'scythe lizard', referring to the gigantic hand claws. This very large theropod dinosaur lived in the late Cretaceous (around 77-69 million years ago). It was one of the last and largest representatives of the Therizinosauria. When fossils were discovered in southwestern Mongolia in the late 1940s (1), Evgeny Maleev thought they belonged to a turtle-like reptile (2). The genus is only from a few bones, including the gigantic hand claws, measuring up to 1 metre long, and parts of the fore and hind limbs.Later finds in northern China allowed paleontologists to assemble the general skeletal structure of the animal, which was determined to be a dinosaur. Some scientists reconstructed it with a head and body like a carnosaur and a killing claw on the foot like a deinonychosaur. When scientists determined that the enigmatic segnosaurs were theropods, this helped clarify the relationships of Therizinosaurus. Some scientists thought that "segnosaurids" were descendants of sauropodomorphs or even were neither saurischians nor ornithischians. New, well-preserved finds showed the bird-like pelvis, feet and skulls of primitive members, helping confirm that segnosaurids belonged to the same group of theropod dinosaurs as Therizinosaurus (and were re-named therizinosaurids) and that therizinosaurs were advanced, herbivorous maniraptoran theropods. It was probably about 7 m (23 ft) long, 3 m (10 ft tall at the hips and weighed about 3 tons. Like other members of its family, Therizinosaurus probably had a small skull atop a long neck, a bipedal gait and a heavy, deep body (as evidenced by the wide pelvis of other therizinosaurids). Its forelimbs may have been 2.5 m (8 ft) long (3). Its hind limbs ended in four weight-bearing toes, unlike other theropod groups, where the first toe was reduced to a dewclaw. Therizinosaurus had three gigantic claws on each digit of its front limbs, with the largest claw probably reaching just under 1 m (3.28 feet) long (1,4,5), larger than any other animal in history. It may have used the claws to defend itself against predators, in intraspecific fighting for territory or mating or to pull leafy tree branches towards its mouth. Therizinosaurus was probably primarily herbivorous (6), but some paleontologists suggest that it used its giant claws to rip open giant termite nests to feed on insects.