Therizinosaurus cheloniformis

"Freddy"
Therizinosaurus cheloniformis

-bloodypencil- schetch

Fossil range: Late Cretaceous, 72–68 Ma


Kingdom: Animalia
Phylum: Chordata
Class: Reptilia
Superorder: Dinosauria
Order: Saurischia
Suborder: Theropoda
Family: †Therizinosauridae
Genus: †Therizinosaurus
Maleev, 1954
Species
T. cheloniformis Maleev, 1954


Therizinosaurus (pronounced /θɛˌrɪzɨnɵˈsɔrəs/ 'scythe lizard', from the Greek therizo meaning 'to reap' or 'to cut off' and sauros meaning 'lizard') is a genus of very large theropod dinosaur. Therizinosaurus lived in the late Cretaceous Period (late Campanian-early Maastrichtian stages, around 70 million years ago), and was one of the last and largest representatives of its unique group, the Therizinosauria. Its fossils were first discovered in Mongolia and they 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.
The first fossil remains of Therizinosaurus were discovered in the late 1940s by a joint Soviet-Mongolian fossil expedition, in the Nemegt Formation of southwestern Mongolia.
The expedition unearthed several giant claws that measured up to a meter in length. These were described by Russian paleontologist Evgeny Maleev in 1954, who thought they belonged to a large, turtle-like reptile.
However, it was not known what creature these belonged to until the early 1950s, when further expeditions unearthed more fossils: several more sets of claws and parts of the fore and hind limbs. Subsequent finds in northern China allowed paleontologists to assemble the general skeletal structure of the animal, which was determined to be a dinosaur and not a turtle.
The discovery that the enigmatic segnosaurs (including Erlikosaurus and Segnosaurus) were actually theropods helped clarify the relationships of Therizinosaurus. Various theories had been proposed to explain the ancestry of the "segnosaurids," with some scientists even suggesting they were descendants of the sauropodomorphs - but new, well-preserved finds such as Alxasaurus in 1993 and Beipiaosaurus in 1996 provided details about the bird-like pelvis, feet and skulls of primitive members, and helped confirm that segnosaurids belonged to the same group of theropod dinosaurs as Therizinosaurus (and were therefore re-named therizinosaurids), and that therizinosaurs were, more specifically, advanced, herbivorous maniraptoran theropods.
Though the fossil remains of Therizinosaurus are incomplete, inferences can be made about its physical characteristics based on related therizinosaurids. Like other members of its family, Therizinosaurus probably had a small skull atop a long neck, with a bipedal gait and a heavy, deep body (as evidenced by the wide pelvis of other therizinosaurids). Its forelimbs may have reached a length of 2.5 meters (8 ft) long. Its hind limbs ended in four weight-bearing toes, unlike other theropod groups, in which the first toe was reduced to a dewclaw.
The most distinctive feature of Therizinosaurus was the presence of three gigantic claws on each digit of its front limbs. These were especially large in Therizinosaurus, and while the largest claw specimens are incomplete, they probably reached just under 1 meter (3.28 feet) in length.