Therizinosaur

Therizinosaurus (meaning "scythe lizard") was a genus of exceptionally big therizinosaurids that existed in Asia roughly 70 million years ago during the Late Cretaceous period in what is now the Nemegt Formation. It is home to Therizinosaurus cheloniformis, a single type species. Therizinosaurus was discovered in 1948 by a Mongolian field trip in the Gobi Desert, and Evgeny Maleev described it in 1954. Only a few bones have been identified in the genus, including large manual unguals (claw bones), from which it derives its name, and other fore and hindlimb parts discos massive therizinosaur that grew up to 9–10 m (30–33 ft) in length and weighed up to 3 t. (3,000 kg). 

It would have been a slow-moving, long-necked high browser with a rhamphotheca (horny beak) and a large torso for food processing, similar to other therizinosaurs. The forelimbs were unusually robust, with three fingers that bore unguals that were rigid, lengthened, and only had major curvatures at the tips, unlike other relatives. Therizinosaurus had the world's longest manual unguals, measuring more than 50 cm (500 mm) in length. It had four functionally weight-bearing toes, unlike other theropod families in which the first toe was reduced to a dewclaw, and it resembled the unrelated sauropodomorphs.

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Therizinosaurus Scientific Classification

Kingdom: Animalia

Phylum: Chordata

Clade: Dinosauria

Clade: Saurischia

Clade: Theropoda

Superfamily: †Therizinosauroidea

Family: †Therizinosauridae

Genus:    †Therizinosaurus

Therizinosaurus Physical Description

Therizinosaurus was large by maniraptoran standards, with estimated lengths of 9 to 10 m (30 to 33 ft) and massive weights ranging from 3 t (3,000 kg) to probably over 5 t. (5,000 kg). Therizinosaurus is the largest therizinosaur and the largest maniraptoran ever discovered. It was the largest maniraptoriform, together with the contemporaneous ornithomimosaur Deinocheirus. Despite the fact that Therizinosaurus' body remains are rather incomplete, generalizations regarding its physical traits can be drawn from more complete and related therizinosaurids. 

Therizinosaurus had a proportionately tiny skull with a rhamphotheca (horny beak) atop its long neck, bipedal gaits, a huge belly for vegetation processing, and scant feathering, similar to other members of its family. A strongly pneumatized (air-filled) vertebral column and a robustly constructed, ophistopubic (backward orientated) pelvis were also likely to be present in Therizinosaurus.

Senter and James employed hindlimb length equations to forecast the total length of Therizinosaurus and Deinocheirus hindlimbs in 2010. They came to the conclusion that an average Therizinosaurus had 3 m (9.8 ft) long legs. Based on comparisons with the cervical vertebrae series of Nanshiungosaurus, Mike Taylor and Matt Wedel proposed that the entire neck would be 2.9 times the size of the humerus, which was 76 cm (760 mm), resulting in a 2.2 m (7.2 ft) long neck.

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Therizinosaurus Hindlimb

Therizinosaurus had a stocky, robust tibia that was somewhat wide at the bottom. The metatarsus was consisted of five metatarsals and was robust and short (nearly sauropodomorph-like). The first four were functional and ended in weight-bearing digits, giving them the name tetradactyl (four-toed). The last metatarsal, also known as the fifth metatarsal, was a significantly reduced bone on the lateral side of the metatarsus with no functional significance. Unlike most other theropods, the first pedal digit was functional and weight-bearing, despite being shorter than the others.

The second and third were both around the same length, while the fourth was a little shorter and thinner. The pedal unguals were flattened on one side and likely acute on the other. Therizinosaurus and other therizinosaurids have distinctive foot morphology, while the general theropod formula comprises tridactyl (three-toed) feet with a decreased first toe that was held off the ground by a dewclaw.

Therizinosaurus Forelimb

Therizinosaurus' arm measured 2.4 metres (7.9 feet) in length (humerus, radius, and second metacarpal with phalanges lengths). With a stocky and flattened dorsal blade, large acromial process (bony extension), and a greatly expanded ventral surface, the scapula measured 67 cm (670 mm) long. A foramen was discovered near the anterior margin of the scapular broadening and the scapulocoracoid suture (bone joint); it presumably served as a route for blood vessels and nerves while the animal was alive. The scapula's posterior edge was thick, and the acromion was thin, indicating that it had been fused into a cartilaginous system with its peripheral in life.

The coracoid had a broad and convex lateral surface that formed a slightly inclined concavity near the scapulocoracoid suture and was 36 cm (360 mm) in length. This concavity curved down towards the broadening of the scapula. This border, like the scapular edge, became very thin towards the scapulocoracoid suture and potentially cartilage along with the coracoid's periphery throughout life. On the coracoid, there was also a huge foramen. The glenoid was large and deep, pointing to the lateral side on the outside. It featured crest-like margins that were thick and convex. The supraglenoid thickness was separated over the top of the scapulocoracoid suture in a convex crest-shaped pattern. A big tubercle with a stocky top developed prominently as the biceps muscle attachment, signifying robust muscles throughout life.

The humerus was large, measuring 76 cm (760 mm) in length. It had a wide upper limit. The deltopectoral crest (deltoid muscle attachment) was especially long and thick, with the top about a third of the way up. The crest was at least two-thirds the length of the entire bone piece. The humerus's lower end was highly flared and enlarged. The condyles were developed on the anterior side of the lower expansion, whereas the epicondyles were quite broad and extended beyond the articular areas' limits. The ulna measured 62.02 cm (620.2 mm), with the straight shaft taking up the majority of its length. The ulnar process was extremely broad.

In a top view, the depression for the upper articulation of the radius limited the lateral side, which had a triangular-shaped border and was slightly concave. The lunar-shaped condyle of the humerus was covered by a semilunar-shaped depression on the inner side. The radius was somewhat S-curved and measured 55.04 cm (550.4 mm). It had a very large upper end that was flattened in a lateral orientation and a very robust distal end.

The first lower carpal bone featured two articulation surfaces on its lowermost end and measured 8.23 cm (82.3 mm) tall and 8.53 cm (85.3 mm) wide. The articulation of the carpus was formed by a large depression on the upper surface of this carpal. It featured a triangular-shaped outline on the inner side that joined to the upper surface of metacarpal I, taking up somewhat less space than the lateral side, which articulates to metacarpal II. An oblique bony protrusion separated these sites. The second lower carpal was smaller than the first, with a height of 5.6 cm (56 mm) and a width of 5.93 cm (59.3 mm).

The metacarpal I measured 14.55 cm (145.5 mm) in length and was stockier than the others. It had a large lateral side, especially at the top, and a thin and narrow inner border. There were three sections to the upper articulation. With a wide and deep hole, the lower articular surface was asymmetric and bent to the inner side from the left one. This metacarpal's overall length was more than 2/3 that of metacarpal III, which may have been a unique feature of Therizinosaurus. Metacarpal II was the most extended and robust metacarpal, measuring 28.68 cm (286.8 mm) in length. It featured an upper articulation that was sloped, square-shaped, and flattened.

In Therizinosaurus, only the second digit of the manus is known. There were two phalanges and a huge ungual on it. The first and second phalanges were similar in size and shape (14.17 cm (141.7 mm) and 14.38 cm (143.8 mm), respectively), and had a robust and stocky structure. The crest on the top articular facets was fairly symmetrical and taller in the first phalanx. The upper border of this crest was quite pointed and thick, and it was most likely where the extensor tendons were attached in life. The lower heads were nearly symmetrical, but the central depression in the first phalanx was much wider and deeper.

Therizinosaurus Habitat

Therizinosaurus fossils have been discovered in the Gobi Desert's well-known Nemegt Formation. Because of the discontinuity of exposures and the lack of datable volcanic rock facies, this formation has never been radiometrically dated. However, the vertebrate fossil assemblage supports an early Maastrichtian stage, possibly between 70 million and 68 million years ago. There are three informal members of the Nemegt Formation. Fluvial sediments make up the lowest member, whereas alluvial plain, paludal, lacustrine, and fluvial sedimentation make up the middle and higher members.

Therizinosaurus lived in a variety of settings, which were determined by the formation's sedimentation, the δ13C level retained on the tooth enamel of many herbivorous dinosaurs, and the abundance of petrified wood. They were characterised by vast meandering and braided rivers, as well as extensive woodlands made up of large, enclosed, canopy-like forests of Araucarias, which provided habitat for herbivorous dinosaurs such as Therizinosaurus. The formation's climate was moderately mild (mean annual temperatures between 7.6 and 8.7 °C), with monsoons bringing cold, dry winters and hot, rainy summers, as well as mean annual precipitations ranging between 775 and 835 mm, with significant seasonal changes.

As demonstrated by the presence of Nemegtomaia in both regions, the moist habitats of the Nemegt Formation may have operated as an oasis-like place that drew oviraptorids from desert neighbouring localities like the Barun Goyot Formation. The Nemegt Formation was formerly thought to be identical to the modern-day Okavango Delta, which is also made up of mesic (well-watered) surroundings.

Because Therizinosaurus remnants have been discovered in fluvial strata, it is thought that it preferred to feed in riparian habitats. Therizinosaurus was one of the tallest dinosaurs in the Nemegt Formation paleofauna due to its notable height and high-browsing habit. It was unlikely to face severe competition for the foliage from other herbivores, but niche partitioning with the formation's titanosaurs—also long-necked dinosaurs—could have happened.

Therizinosaurus Arms and Claws Function

Maleev thought the exceptionally huge claws were employed to pick seaweed when he initially described them in 1954. This, on the other hand, is based on the notion of a massive marine turtle. Rozhdestvensky reexamined the claws in 1970 and proposed a purpose specialised in opening termite mounds or a frugivore diet as a conceivable function. In 1976, Barsbold speculated that Therizinosaurus' unique claws may have been used to impale or dig up loose terrain, but he also noted the creature's infamous weakness when struck. Lev A. Nessov proposed in 1995 that the elongated claws were employed for predator defence and that juveniles may have used their claws for arboreal movement, akin to modern-day sloths or hoatzin chicks.

Lautenschlager used digital models to examine the function of various therizinosaur hand claws, including Therizinosaurus, in 2014. With a force of 400 N applied to each claw morphology, three different functional situations were simulated: scratch/digging, hook-and-pull, and piercing. Though Alxasaurus' stocky claws resulted in low-stress magnitudes, Falcarius, Nothronychus, and Therizinosaurus' claw curvature and elongation resulted in higher stress magnitudes.

Lautenschlager observed that several therizinosaurian taxa's claws were poorly functioning in a scratch/digging manner, indicating that this was the most unlikely function. Though some dinosaur species have been claimed to engage in fossorial (digging) activity, therizinosaurs' enormous bodies rule out the likelihood of burrowing. Instead of fossorial activity, Therizinosaurus' hands are more likely to be utilised in a hook-and-pull method to pull or hold vegetation within reach. Therizinosaurs would be most comparable to existing anteaters and extinct ground sloths because of their herbivorous behaviour.

Given the paucity of more specimens, Lautenschlager could neither confirm nor deny that the hand claws were used for defence, intraspecific rivalry, stabilisation by holding tree trunks during high browsing, sexual dimorphism, or clutching mates during mating. He noted that there is no proof that Therizinosaurus' long claws were used in active defence or assault; nonetheless, these appendages could have played a function in the face of a threat, such as intimidation.

Based on bending resistance studies of different dinosaur humeri, Scott A. Lee and Zachary Richards discovered that the humeri of carnosaur, therizinosaur, and tyrannosaur dinosaurs are relatively stress-resistant. Therizinosaurus and kindred therizinosaurians used their arms in a powerful manner that created considerable forces, as evidenced by their greater ability to tolerate stress. They also speculated that some members' prominent claws may have served as protection against predators as well as other uses. Unlike the lighter and more agile ornithomimosaurs, which used speed to dodge predators, Therizinosaurus and its cousins relied on their arms and claws to defend themselves. 

Therizinosaurus Feeding Habits

Dale A. Russell and Donald E. Russell studied Therizinosaurus and Chalicotherium (the species studied in this study is now known as Anisodon) in 1993 and found similarities in their body plans, despite the fact that they belong to separate genera. The pelvic girdle was substantial and adapted for a sitting activity in both taxa, while the hindlimb (especially the foot) anatomy was robust and shorter. They thought these adaptations between extinct mammal and dinosaur genera were an example of convergent evolution, which occurs when animals evolve similar traits without necessarily being related.

Furthermore, modern-day gorillas have a body layout similar to this. The authors proposed that Therizinosaurus lead a herbivorous lifestyle because animals with this body design are known to be herbivores. Russell and Russell rebuilt Therizinosaurus' feeding behaviour as being able to sit while eating huge plants and trees. The plant material would have been picked with its hands, and its lengthened neck would have aided this action by preventing the application of excessive force and effort.

Because its arms were long enough to touch the ground in some positions, they may have assisted the dinosaur in rising from a prone position. Therizinosaurus may have been able to reach even higher plants when browsing in a bipedal stance, thanks to its short and powerful feet. Because of its long claws, Therizinosaurus was better at pushing big clumps of leaves than Chalicotherium was at hooking branches. It's also likely that Therizinosaurus' movements were less precise than Chalicotherium's, owing to the latter's better-developed brain, dentition, and muscular capacities.