Therizinosaurus

Therizinosaurus (/ˌθɛrɪˌzɪnoʊˈsɔːrəs/; 'scythe lizard', from Ancient Greek θερίζω, meaning 'to reap', and σαῦρος, meaning 'lizard') 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.

Therizinosaurus
Therizinosaurus reconstruction by Mario Lanzas 2018
Therizinosaurus
Temporal range: Late Cretaceous, 70–66 Ma
Therizinosaurus arms
Fossil forelimbs
Scientific classification
Kingdom: Animalia
Phylum: Chordata
Clade: Dinosauria
Order: Saurischia
Suborder: Theropoda
Family: Therizinosauridae
Genus: Therizinosaurus
Maleev, 1954
Species:
T. cheloniformis
Binomial name
Therizinosaurus cheloniformis
Maleev, 1954

Description

Therizinosaurus scale
Size comparison

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)[1] or even 3.5 metres (11.5 feet) in the largest known specimen.[2] 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 tonnes in weight.[2] They are the largest therizinosaurs known, and the largest known maniraptorans.[2]

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 therizinosaurs 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.[3] The claws were relatively straight, only gradually tapering into a point, as well as extremely narrow and transversely flattened.[2][4][5][6]

The feeding habits of Therizinosaurus are unknown since no skull material has ever been found that could indicate their diet. However, like other therizinosaurs, they were most likely herbivorous.[7]

History

Therizinosaurus claw
Cast of a hand

The first fossil remains of Therizinosaurus were discovered in 1948 by a joint Soviet-Mongolian fossil expedition, in the Nemegt Formation of southwestern Mongolia.[4] The expedition unearthed several giant claws that measured, including presumed horn sheaths, up to a metre in length. These were named and described by the Russian paleontologist Evgeny Maleev in 1954, who thought they belonged to a large diving turtle-like reptile, 4.5 metres long, that used the claws to harvest seaweed. The holotype specimen, PIN no. 551-483, consisted of the claws.[3] However, it was not understood what general kind of creature these belonged to until 1970, when Anatoly Konstantinovich Rozhdestvensky determined it to be a theropod dinosaur and not a turtle.[5] Nevertheless, the precise kind of dinosaur it was remained a controversial issue. Some reconstructed it with a head and body like a carnosaur and a killing claw on the foot like a deinonychosaur.

Therizinosaurus known material
Skeletal reconstruction showing known elements

Further expeditions unearthed more fossils. The first were specimens IGM 100/15-17: several more sets of claws and parts of the forelimbs, described by Rinchen Barsbold in 1976.[1] Another find was specimen IGM 100/45, consisting of hindlimbs, described by Altangerel Perle in 1982.[8] Subsequently, finds in northern China of related species allowed paleontologists to assemble the general skeletal structure of the animal. The discovery that these enigmatic segnosaurs (including Erlikosaurus and Segnosaurus) were actually theropods helped clarify the relationships of Therizinosaurus. Various theories were proposed to explain the ancestry of the "segnosaurids", with some scientists suggesting they were descendants of the sauropodomorphs or even that they were neither saurischians nor ornithischians. However, 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 renamed therizinosaurids), and that therizinosaurs were, more specifically, advanced, herbivorous maniraptoran theropods.

Phylogeny

Therizinosaurus NT
Restoration

In 1954, Therizinosaurus was assigned by Maleev to the Therizinosauridae.[3] Later, the Therizinosauridae were identified with the Segnosauridae, the former name having priority. Relationships within the Therizinosauridae are difficult to determine, due to the paucity of remains known from Therizinosaurus itself.[9]

The cladogram presented here follows a 2007 phylogenetic analysis by Phil Senter.[10]

Therizinosauridae

Erliansaurus

Nothronychus

unnamed

Neimongosaurus

unnamed

Segnosaurus

unnamed

Erlikosaurus

Therizinosaurus

See also

References

  1. ^ a b Barsbold, R. (1976c). "New data on Therizinosaurus (Therizinosauridae, Theropoda) [in Russian]." In Devâtkin, E.V. and N.M. Ânovskaâ (eds.), Paleontologiâ i biostratigrafiâ Mongolii. Trudy, Sovmestnaâ Sovetsko−Mongol’skaâ paleontologičeskaâ kspediciâ, 3: 76–92.
  2. ^ a b c d Paul, G.S., 2010, The Princeton Field Guide to Dinosaurs, Princeton University Press p. 160
  3. ^ a b c Maleev, E.A. (1954). "New turtle−like reptile in Mongolia [in Russian]." Priroda, 1954(3): 106–108.
  4. ^ a b Barsbold, R. (1983). "Carnivorous dinosaurs from the Cretaceous of Mongolia [in Russian]." Trudy, Sovmestnaâ Sovetsko−Mongol’skaâ paleontologičeskaâ èkspediciâ, 19: 1–120.
  5. ^ a b Rozhdestvensky, A.K. (1970). "On the gigantic claws of mysterious Mesozoic reptiles." Paleontologischeskii Zhurnal, 1970(1): 131-141.
  6. ^ Rozhdestvensky, A.K. (1970). "Giant claws of Enigmatic Mesozoic Reptiles." Paleontology Journal, 4(1): 117-125.
  7. ^ Svarney, T.E. and Svarney, P.B. (2003). "The Handy Dinosaur Answer Book", 1st ed. Canton, MI: Visible Ink Press.
  8. ^ Perle, A., 1982, "On a new finding of the hindlimb of Therizinosaurus sp. from the Late Cretaceous of Mongolia", Problems on the Geology of Mongolia, 5: 94–98
  9. ^ Lindsay E. Zanno (2010). "A taxonomic and phylogenetic re-evaluation of Therizinosauria (Dinosauria: Maniraptora)". Journal of Systematic Palaeontology. 8 (4): 503–543. doi:10.1080/14772019.2010.488045.
  10. ^ Senter, P. (2007). "A new look at the phylogeny of Coelurosauria (Dinosauria: Theropoda)." Journal of Systematic Palaeontology, (doi:10.1017/S1477201907002143).
1948 in archaeology

The year 1948 in archaeology involved some significant events.

1954 in paleontology

Paleontology or palaeontology (from Greek: paleo, "ancient"; ontos, "being"; and logos, "knowledge") is the study of prehistoric life forms on Earth through the examination of plant and animal fossils. This includes the study of body fossils, tracks (ichnites), burrows, cast-off parts, fossilised feces (coprolites), palynomorphs and chemical residues. Because humans have encountered fossils for millennia, paleontology has a long history both before and after becoming formalized as a science. This article records significant discoveries and events related to paleontology that occurred or were published in the year 1954.

Alxasaurus

Alxasaurus (; "Alxa Desert lizard") is a genus of therizinosauroid alxasaurid theropod dinosaur from the Early Cretaceous (Albian) Bayin-Gobi Formation in Inner Mongolia. It is one of the earliest known members of the superfamily Therizinosauroidea, but it already possessed the body shape - including the long neck, short tail, and long hand claws - of later therizinosauroids. Like other members of this group, it was a bipedal herbivore with a large gut to process plant material. Several specimens are known and the largest was a little over 3.8 metres (12 feet) long. According to Gregory S. Paul, it was 4 metres (13 feet) long and its weight was about 400 kilograms (880 pounds).

Chased by Dinosaurs

Chased by Dinosaurs is a two-episode spin-off of the BBC program Walking with Dinosaurs which originally aired on BBC One during Christmas 2002 and November 2003. In a departure from the series usual format, these specials feature zoologist Nigel Marven as a time traveller who investigates and encounters dinosaurs in the wild. The specials are known only by their individual titles (with the subtitle 'A Walking With Dinosaurs Special/Trilogy') on-screen; The umbrella title 'Chased by Dinosaurs' was used to market the series in the United States.

The production company Impossible Pictures and producer Jasper James would produce the ITV series Prehistoric Park in 2006. This docu-fiction series would also feature Marven traveling through prehistory in search of extinct animals.

Claw

A claw is a curved, pointed appendage, found at the end of a toe or finger in most amniotes (mammals, reptiles, birds).

Some invertebrates such as beetles and spiders have somewhat similar fine hooked structures at the end of the leg or tarsus for gripping a surface as the creature walks. Crabs', lobsters' and scorpions' pincers, or more formally, their chelae, are sometimes called claws.

A true claw is made of hard protein called keratin. Claws are used to catch and hold prey in carnivorous mammals such as cats and dogs, but may also be used for such purposes as digging, climbing trees, self-defense, and grooming, in those and other species.

Similar appendages that are flat and do not come to a sharp point are called nails instead. Claw-like projections that do not form at the end of digits, but spring from other parts of the foot are properly named spurs.

Coelurosauria

Coelurosauria (; from Greek, meaning "hollow tailed lizards") is the clade containing all theropod dinosaurs more closely related to birds than to carnosaurs.

Coelurosauria is a subgroup of theropod dinosaurs that includes compsognathids, tyrannosaurs, ornithomimosaurs, and maniraptorans; Maniraptora includes birds, the only dinosaur group alive today.Most feathered dinosaurs discovered so far have been coelurosaurs. Philip J. Currie considers it probable that all coelurosaurs were feathered. In the past, Coelurosauria was used to refer to all small theropods, but this classification has since been abolished.

Deinocheirus

Deinocheirus ( DY-no-KY-rəs) is a genus of large ornithomimosaur that lived during the Late Cretaceous around 70 million years ago. In 1965, a pair of large arms, shoulder girdles, and a few other bones of a new dinosaur were first discovered in the Nemegt Formation of Mongolia. In 1970, this specimen became the holotype of the only species within the genus, Deinocheirus mirificus; the genus name is Greek for "horrible hand". No further remains were discovered for almost fifty years, and its nature remained a mystery. Two more complete specimens were described in 2014, which shed light on many aspects of the animal. Parts of these new specimens had been looted from Mongolia some years before, but were repatriated in 2014.

Deinocheirus was an unusual ornithomimosaur, the largest of the clade at 11 m (36 ft) long, and weighing 6.4 t (7.1 short tons). Though it was a bulky animal, it had many hollow bones which saved weight. The arms were among the largest of any bipedal dinosaur at 2.4 m (7.9 ft) long, with large, blunt claws on its three-fingered hands. The legs were relatively short, and bore blunt claws. Its vertebrae had tall neural spines that formed a "sail" along its back. The tail ended in pygostyle-like vertebrae, which indicate the presence of a fan of feathers. The skull was 1.024 m (3.36 ft) long, with a wide bill and a deep lower jaw, similar to those of hadrosaurs.

The classification of Deinocheirus was long uncertain, and it was initially placed in the theropod group Carnosauria, but similarities with ornithomimosaurians were soon noted. After more complete remains were found, Deinocheirus was shown to be a primitive ornithomimosaurian, most closely related to the smaller genera Garudimimus and Beishanlong, together forming the family Deinocheiridae. Members of this group were not adapted for speed, unlike other ornithomimosaurs. Deinocheirus is thought to have been omnivorous; its skull shape indicates a diet of plants, fish scales were found in association with one specimen and gastroliths were also present in the stomach region of the specimen. The large claws may have been used for digging and gathering plants. Bite marks on Deinocheirus bones have been attributed to the tyrannosaurid Tarbosaurus.

Evgeny Maleev

Evgeny/Evgenii Aleksandrovich Maleev [1] (Russian: Евгений Александрович Малеев, pronounced [jɪˈvɡenʲɪj ɐlʲɪˈksandrəvʲɪtɕ mɐˈlʲeɪf]; 25 February 1915 – 12 April 1966) was a Soviet paleontologist who named the ankylosaur Talarurus; the theropods Tarbosaurus and Therizinosaurus; and the family Therizinosauridae.

Maleev did research on Tarbosaurus brains by cutting open fossilized braincases with a diamond saw. Modern researchers use computer tomography scans and 3D reconstruction software to visualize the interior of dinosaur endocrania, thus eliminating the need to damage valuable specimens.Two dinosaurs — Maleevus and Maleevosaurus — have been named for Maleev.

List of Dino Dan episodes

Dino Dan is a Canadian television series that was created and is directed by J. J. Johnson. The series premiered on TVOKids in Canada on January 4, 2010 and on Nick Jr. in the United States on October 17, 2010. A third season of the series, Dino Dana, has been aired on TVOKids in Canada and instead of being aired on Nick Jr. in the United States, it is streamed on Amazon.com in the United States.

List of creatures by Impossible Pictures

The following is a complete list of prehistoric creatures from the universe of the Walking with... series documentary, science fiction and fantasy television programmes, companion books and also any spin-off merchandise. Most of the shows produced by Impossible Pictures with BBC Worldwide and Discovery Channel in association with ProSieben and France 3 and created by Tim Haines and Jasper James. They used visual effects teams such as Framestore, The Mill and Jellyfish Pictures to bring back extinct creatures to life.

Nemegt Formation

The Nemegt Formation (or Nemegtskaya Svita) is a geological formation in the Gobi Desert of Mongolia, dating to the Late Cretaceous. It overlies and sometimes interfingers with the Barun Goyot Formation. Interfingering has been noted at the stratotype (Red Walls) and Khermeen Tsav. It consists of river channel sediments and contains fossils of fish, turtles, crocodilians, and a diverse fauna of dinosaurs, including birds. The climate associated with it was wetter than when preceding formations were deposited; there seems to have existed at least some degree of forest cover. Fossilized trunks have been also found.

There has been no absolute dating of the Nemegt Formation. It is, however, almost certainly early Maastrichtian c 71-70 Ma. Gradzinski and others considered a Campanian age possible but more recent research indicates otherwise. A Campanian age no longer seems credible, because the Alagteegian (or lower Djadokhtan, at the locality "Chuluut Uul") has been radiometrically dated at about 73.5 Ma or even younger (a more recent K/Ar date is 71.6 +/- 1.6 Ma). The c 73.5 (or perhaps 72) Ma Alagteegian is separated from the Nemegt by the "classic" Djadokhtan (e.g. Bayan Dzag), later Djadohktan (represented by Ukhaa Tolgod) and Barungoyotian (Khulsan). All these intervening horizons almost certainly represent more than the 1.5 million years between the dated Alagteegian level and the onset of Maastrichtian time (72.1 million Ma according to current dating). Ergo the Nemegt is entirely Maastrichtian. See also Shuvalov, Sochava and Martinsson The Age of Dinosaurs in Russia and Mongolia. The presence of Saurolophus further supports an early Maastrichtian age as the same genus occurs in the early Maastrichtian Horseshoe Canyon formation.

Nemegtosaurus

Nemegtosaurus (meaning 'Reptile from the Nemegt') was a sauropod dinosaur from Late Cretaceous Period of what is now Mongolia. Nemegtosaurus was named after the Nemegt Basin in the Gobi Desert, where the remains — a single skull — were found. The skull resembles diplodocoids in being long and low, with pencil-shaped teeth. However, recent work has shown that Nemegtosaurus is in fact a titanosaur, closely related to animals such as Saltasaurus, Alamosaurus and Rapetosaurus.

Segnosaurus

Segnosaurus ('slow lizard') is a genus of herbivorous theropod dinosaur belonging to the Therizinosauridae from the Cretaceous of Mongolia.

Suzhousaurus

Suzhousaurus is a genus of herbivorous therizinosauroid theropod dinosaur from the Early Cretaceous-age Xinminpu Group of the Yujingzi Basin, Gansu, China.

Therizinosauria

Therizinosaurs (or segnosaurs) were theropod dinosaurs belonging to the clade Therizinosauria. Therizinosaur fossils have been found in Early through Late Cretaceous deposits in Mongolia, the People's Republic of China, western North America and possibly Australia . Various features of the forelimbs, skull and pelvis unite these finds as both theropods and as maniraptorans, close relatives to birds.

The name therizinosaur is derived from the Greek θερίζω therízein, meaning 'to reap' or 'to cut off', and σαῦρος saûros meaning 'lizard'. The older name segnosaur is derived from Latin segnis meaning 'slow' or 'sluggish', and Greek σαυρος, sauros, meaning 'lizard'.

Therizinosauridae

Therizinosauridae ("reaper lizards") is a family of theropod dinosaurs whose fossil remains have been dated to the Mid-to-Late Cretaceous period (100 to 70 mya). Even though representative fossils have only been found throughout China, Mongolia, and the United States, the range of Therizinosauridae was believed to have spanned much of the supercontinent of Laurasia at its height.Therizinosauridae was named after the large, claw-bearing ungual found on the manus of members in the group. This feature has led to little insight about the ecology of the family, and the purpose of the claw remains unknown. Other notable aspects of the physiology of these animals include a modified pelvis, robust hind-limbs, and a highly derived, nearly avian inner-ear. Moreover, the larger superfamily of Therizinosauroidea is believed to be the earliest group in which simple feathers have been documented.Research into therizinosaurids has also focused on uncovering more about the unique ecology and paleobiology of the family. A fair portion of modern research has concentrated on the feeding-patterns of these reptiles, as they are considered to be the best regarded candidate for the emergence of herbivory within Theropoda. While many closely related taxa are carnivorous, it is thought that the members of Therizinosauroidea, including Therizinosauridae, diverged and adopted either an herbivorous or omnivorous lifestyle.The current scientific consensus is that therizinosaurids evolved from small, bird-like maniraptorans, and thus they fall within the coelurosaurian clade called Maniraptora. Most studies have concluded that within Maniraptora, Therizinosaurians were the first of five major groups to diverge.

Timeline of therizinosaur research

This timeline of therizinosaur research is a chronological listing of events in the history of paleontology focused on the therizinosaurs, unusually long-necked, pot-bellied, and large-clawed herbivorous theropod dinosaurs closely related to birds. The early history of therizinosaur research occurred in three phases. The first phase was the discovery of scanty and puzzling fossils in Asia by the Central Asiatic Expeditions of the 1920s and Soviet-backed research in the 1950s. This phase resulted in the discovery of the Therizinosaurus cheloniformis type specimen. Soviet paleontologist Evgeny Maleev interpreted these unusual remains as belonging to some kind of gigantic turtle.The second major phase of therizinosaur research followed the discovery of better preserved remains in the 1970s by collaborative research between the Soviets and Mongolians. These finds revealed the true nature of therizinosaurs as bizarre dinosaurs. However, the exact nature and classification of therizinosaurs within Dinosauria was controversial as was their paleobiology. When Rozhdestventsky first reinterpreted therizinosaurs as dinosaurs he argued that they were unusual theropods that may have used their clawed arms to break open termite mounds or collect fruit. Osmolska and Roniewicz also considered therizinosaurs to be theropods.In 1979, Altangerel Perle named the new species Segnosaurus galbinensis, which although he recognized was an unusual theropod, he did not recognize as a therizinosaur. Consequently, he named the new family Segnosauridae and, in 1980, Segnosauria. Two years later, Perle recognized commonalities between Therizinosaurus and segnosaurs, reclassifying the former as a member of the latter. From hereout therizinosaur research was considered "segnosaur" research. Perle himself thought that his "segnosaurs" were semi-aquatic fish-eaters. However, in the early 1990s, researchers like Rinchen Barsbold and Teresa Maryańska cast doubt on the connection between therizinosaurs and segnosaurs altogether.Nevertheless, the description Alxasaurus elsitaiensis provided more evidence for a close relationship between the therizinosaurs and "segnosaurs" and led to a revision of their classification. The discovery of this and other primitive therizinosaurs in China formed the beginnings of the third major wave of therizinosaur research. That same year Russell and Russell reinterpreted therizinosaurs as herbivorous foragers like mammalian chalicotherium. Other significant finds of the 1990s include therizinosaur eggs with embryos preserved inside and the first known therizinosaur with feathers, Beipiaosaurus, which was described from China in 1999.

Basal therizinosaurs
Therizinosauroidea

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