Therizinosaurus

{{italictitle}}
{{italictitle}}{{Taxobox
| name = Therizinosaurus
| image = Therizinosaurus clawcast aus.jpg
| image_width = 250px
| image_caption = Cast of a Therizinosaurus cheloniformis claw at the Australian Museum

Australian Museum

The Australian Museum is the oldest museum in Australia, with an international reputation in the fields of natural history and anthropology. It features collections of vertebrate and invertebrate zoology, as well as mineralogy, palaeontology, and anthropology...

, Sydney

Sydney

Sydney is the largest city in Australia, and the state capital of New South Wales. Sydney has a metropolitan area population of approximately 4.34 million and an area of approximately 12,000 square kilometres. Its inhabitants are called Sydneysiders, and Sydney is often called "the Harbour City"...

| fossil_range = Late Cretaceous

Late Cretaceous

The Late Cretaceous is the youngest of two epochs in which the Cretaceous period is divided in the geologic timescale. Rock strata from this epoch form the Upper Cretaceous series...

, {{fossil range|72|68}}
| regnum = Animal

Animal

Animals are a major group of mostly multicellular, eukaryotic organisms of the kingdom Animalia or Metazoa. Their body plan eventually becomes fixed as they develop, although some undergo a process of metamorphosis later on in their life. Most animals are motile, meaning they can move spontaneously...

ia
| phylum = Chordata

Chordate

Chordates are animals which are either vertebrates or one of several closely related invertebrates. They are united by having, for at least some period of their life cycle, a notochord, a hollow dorsal nerve cord, pharyngeal slits, an endostyle, and a post-anal tail...

| classis = Reptilia

Reptile

Reptiles, or members of the class Reptilia, are air-breathing, generally "cold-blooded" amniotes that generally have skin covered in scales or scutes. They are tetrapods and lay amniote eggs, whose embryos are surrounded by the amnion membrane...

| superordo = Dinosaur

Dinosaur

{{Otheruses}}{{pp-semi-protected|small=yes}}{{Otheruses}}{{pp-semi-protected|small=yes}}{{Taxobox|name = Dinosaurs|fossil_range = {{Fossil range|230|65|earliest=230|latest=0|PS=
Descendant taxon Aves survives to present.}}|image = field_dinos_2.jpg...

ia
| ordo = Saurischia

Saurischia

Saurischia is one of the two orders, or basic divisions, of dinosaurs. In 1888, Harry Seeley classified dinosaurs into two orders, based on their hip structure...

| subordo = Theropoda

Theropoda

Theropods are a group of bipedal saurischian dinosaurs. Although they were primarily carnivorous, a number of theropod families evolved herbivory during the Cretaceous Period...

| familia = Therizinosauridae

Therizinosauridae

Therizinosauridae is a family of advanced herbivorous or omnivorous theropod dinosaurs. Therizinosaurid fossil remains have been recovered from mid-late Cretaceous Period deposits from Mongolia, China, and the United States.-Classification:...

| genus = Therizinosaurus
| genus_authority = Maleev

Evgeny Maleev

Evgeny Aleksandrovich Maleev was a Russian paleontologist who named the armoured dinosaur Talarurus, the fearsome Tarbosaurus, and the enigmatic Therizinosaurus....

, 1954
| subdivision_ranks = Species

Species

In biology, a species is:* a taxonomic rank or* a unit at that rank ....

| subdivision =
T. cheloniformis Maleev, 1954 (type

Type species

In taxonomy, a type species is a technical phrase, involved in the application of formal names...

)
}}

Therizinosaurus ({{pron-en|θɛˌrɪzɨnɵˈsɔrəs}} 'scythe lizard', from the Greek

Ancient Greek

Ancient Greek is the historical stage in the development of the Greek language spanning across the Archaic , Classical , and Hellenistic periods of ancient Greece and the ancient world. It is predated in the 2nd millennium BC by Mycenaean Greek...

 therizo meaning 'to reap' or 'to cut off' and sauros meaning 'lizard') is a genus

Genus

In biology, a genus is a taxonomic unit used in the classification of living and fossil organisms. The term comes from Latin genus "descent, family, type, gender" , cognate with – genos, "race, stock, kin" ..In addition, genus is a taxonomic rank in the hierarchy In biology, a genus (plural:...

 of very large theropod dinosaur

Dinosaur

{{Otheruses}}{{pp-semi-protected|small=yes}}{{Otheruses}}{{pp-semi-protected|small=yes}}{{Taxobox|name = Dinosaurs|fossil_range = {{Fossil range|230|65|earliest=230|latest=0|PS=
Descendant taxon Aves survives to present.}}|image = field_dinos_2.jpg...

. Therizinosaurus lived in the late Cretaceous

Cretaceous

The Cretaceous , Latin language for "chalky", usually abbreviated K for its German translation Kreide , is a geologic period and system from circa to million years ago . In the geologic timescale, the Cretaceous follows on the Jurassic period and is followed by the Paleogene period of the...

 Period (late Campanian

Campanian

The Campanian is, in the ICS' geologic timescale, the fifth of six ages of the Late Cretaceous epoch . The Campanian spans the time from 83.5 ± 0.7 Ma to 70.6 ± 0.6 Ma ...

-early Maastrichtian

Maastrichtian

The Maastrichtian is, in the ICS' geologic timescale, the latest age or upper stage of the Late Cretaceous epoch or Upper Cretaceous series, the Cretaceous period or system, and of the Mesozoic era or erathem. It spanned from 70.6 ± 0.6 Ma to 65.5 ± 0.3 Ma...

 stages, around 70 million years ago), and was one of the last and largest representatives of its unique group, the Therizinosaur

Therizinosaur

Therizinosaurs are theropod dinosaurs belonging to the clade Therizinosauroidea. Therizinosaur fossils have been found in Early through Late Cretaceous deposits in Mongolia, the People's Republic of China and Western North America...

ia. Its fossil

Fossil

Fossils are the preserved remains or traces of animals, plants, and other organisms from the remote past. The totality of fossils, both discovered and undiscovered, and their placement in fossiliferous rock formations and sedimentary layers is known as the fossil record...

s were first discovered in Mongolia

Mongolia

Mongolia is a landlocked country in East and Central Asia. It borders Russia to the north and the People's Republic of China to the south, east and west. Although Mongolia does not share a border with Kazakhstan, its western-most point is only 24 miles from Kazakhstan's eastern tip. Ulan Bator,...

 and they were originally thought to belong to a turtle

Turtle

Turtles are reptiles of the order Testudines , characterised by a special bony or cartilaginous shell developed from their ribs that acts as a shield...

-like reptile (hence the species

Species

In biology, a species is:* a taxonomic rank or* a unit at that rank ....

 name, T. cheloniformis — "turtle-formed"). It is known only from a few bones, including gigantic hand claws, from which it gets its name.

Discovery and species

The first fossil

Fossil

Fossils are the preserved remains or traces of animals, plants, and other organisms from the remote past. The totality of fossils, both discovered and undiscovered, and their placement in fossiliferous rock formations and sedimentary layers is known as the fossil record...

 remains of Therizinosaurus were discovered in the late 1940s by a joint Soviet-Mongolian fossil

Fossil

Fossils are the preserved remains or traces of animals, plants, and other organisms from the remote past. The totality of fossils, both discovered and undiscovered, and their placement in fossiliferous rock formations and sedimentary layers is known as the fossil record...

 expedition, in the Nemegt Formation

Nemegt Formation

The Nemegt Formation is a geological formation dating from the Late Cretaceous sedimentary from the Gobi Desert of Mongolia. It overlies and sometimes forms folds with the Barun Goyot Formation. It consists of river channel sediments and contains fossils of fish, turtles, crocodilians, birds and a...

 of southwestern Mongolia

Mongolia

Mongolia is a landlocked country in East and Central Asia. It borders Russia to the north and the People's Republic of China to the south, east and west. Although Mongolia does not share a border with Kazakhstan, its western-most point is only 24 miles from Kazakhstan's eastern tip. Ulan Bator,...

. The expedition unearthed several giant claw

Claw

A claw is a curved, pointed appendage, found at the end of a toe or finger in most mammals, birds, and some reptiles. However, the word "claw" is also often used in reference to an invertebrate. Somewhat similar fine hooked structures are found in arthropods such as beetles and spiders, at the end...

s that measured up to a meter in length. These were described by Russian paleontologist Evgeny Maleev

Evgeny Maleev

Evgeny Aleksandrovich Maleev was a Russian paleontologist who named the armoured dinosaur Talarurus, the fearsome Tarbosaurus, and the enigmatic Therizinosaurus....

 in 1954, who thought they belonged to a large, turtle

Turtle

Turtles are reptiles of the order Testudines , characterised by a special bony or cartilaginous shell developed from their ribs that acts as a shield...

-like reptile

Reptile

Reptiles, or members of the class Reptilia, are air-breathing, generally "cold-blooded" amniotes that generally have skin covered in scales or scutes. They are tetrapods and lay amniote eggs, whose embryos are surrounded by the amnion membrane...

. 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

China

China is a cultural region, an ancient civilization, and, depending on perspective, a national or multinational entity extending over a large area in East Asia....

 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

Erlikosaurus

Erlikosaurus is a genus of dinosaur from the late Cretaceous Period, belonging to the family Therizinosauridae. Its fossils, a skull and some post-cranial fragments, were found in the Bayan Shireh Formation of Mongolia, dating to about 80 million years ago.The type species, E. andrewsi, was...

and Segnosaurus

Segnosaurus

Segnosaurus is a genus of theropod dinosaur belonging to the family Therizinosauridae. The type species, S. galinensis, was described in 1979 by Dr. A. Perle...

) 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

Sauropodomorpha

The Sauropodomorpha were a group of long-necked, herbivorous dinosaurs that eventually dropped down on all fours and became the largest animals that ever walked the earth.- Description :...

 - but new, well-preserved finds such as Alxasaurus

Alxasaurus

Alxasaurus is a genus of therizinosauroid theropod dinosaur from the Early Cretaceous Period of Inner Mongolia. It is one of the earliest known members of the superfamily Therizinosauroidea, but it still possessed the body shape - including the long neck, short tail, and long hand claws - of later...

in 1993 and Beipiaosaurus

Beipiaosaurus

Beipiaosaurus is a genus of therizinosauroid theropod dinosaur. The discovery of Beipiaosaurus , which translates as "Beipiao lizard" after a city in China near the location of its discovery, was announced in the May 27, 1999, issue of the journal Nature...

in 1996 provided details about the bird-like pelvis

Pelvis

In human anatomy, the pelvis is the part of the trunk inferioposterior to the abdomen in the transition area between the trunk and the lower limbs...

, 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 maniraptora

Maniraptora

Maniraptora is a clade of coelurosaurian dinosaurs which includes the birds and the dinosaurs that were more closely related to them than to Ornithomimus velox. It contains the major subgroups Avialae, Deinonychosauria, Oviraptorosauria and Therizinosauria. Ornitholestes and the Alvarezsauridae...

n theropods.

Characteristics

Though the fossil remains of Therizinosaurus are incomplete, inferences can be made about its physical characteristics based on related therizinosaurids

Therizinosauridae

Therizinosauridae is a family of advanced herbivorous or omnivorous theropod dinosaurs. Therizinosaurid fossil remains have been recovered from mid-late Cretaceous Period deposits from Mongolia, China, and the United States.-Classification:...

. Like other members of its family, Therizinosaurus probably had a small skull atop a long neck, with a biped

Biped

Bipedalism is a form of terrestrial locomotion where an organism moves by means of its two rear limbs, or legs. An animal or machine that usually moves in a bipedal manner is known as a biped , meaning "two feet"...

al gait and a heavy, deep body (as evidenced by the wide pelvis

Pelvis

In human anatomy, the pelvis is the part of the trunk inferioposterior to the abdomen in the transition area between the trunk and the lower limbs...

 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

Dewclaw

A dewclaw is a vestigial digit of the foot of many mammals, birds, and reptiles . It grows higher on the leg so that in digitigrade species, when the animal is standing, it does not make contact with the ground.-Dogs:Dogs almost always have dewclaws on the inside of the front legs and occasionally...

.

The most distinctive feature of Therizinosaurus was the presence of three gigantic claw

Claw

A claw is a curved, pointed appendage, found at the end of a toe or finger in most mammals, birds, and some reptiles. However, the word "claw" is also often used in reference to an invertebrate. Somewhat similar fine hooked structures are found in arthropods such as beetles and spiders, at the end...

s 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.

Paleobiology

The feeding habits of Therizinosaurus are unknown, since no skull material has ever been found that could indicate its diet. However, like other therizinosaurs, it was probably primarily herbivorous

Herbivore

A herbivore is an animal that is adapted to eat plants and not meat.Herbivory is a form of predation in which an organism consumes principally autotrophs such as plants, algae and photosynthesizing bacteria....

. There are other possible functions that could have been served by the claws of Therizinosaurus, such as defense against predators (e.g. the contemporary Tarbosaurus

Tarbosaurus

Tarbosaurus is a genus of tyrannosaurid theropod dinosaur that flourished in Asia between 70 and 65 million years ago, at the end of the Late Cretaceous Period. Fossils have been recovered in Mongolia with more fragmentary remains found further afield in parts of China...

) and in intraspecific fighting, such as fighting for territory or for mating, or to pull leafy tree branches towards its mouth. The claws may even have served all these functions.