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128-574: Therizinosaurs ( ; once called segnosaurs ) are an extinct group of large herbivorous theropod dinosaurs whose fossils have been mainly discovered from Cretaceous deposits in Asia and North America . Potential fragmentary remains have also been found in Jurassic deposits of Asia and Europe . Various features of the forelimbs, skull and pelvis unite these finds as both theropods and maniraptorans , making them relatives of birds . The name of
256-695: A Compsognathus longipes fossil was found with a lizard in its stomach, and a Velociraptor mongoliensis specimen was found locked in combat with a Protoceratops andrewsi (a type of ornithischian dinosaur). The first confirmed non-carnivorous fossil theropods found were the therizinosaurs , originally known as "segnosaurs". First thought to be prosauropods , these enigmatic dinosaurs were later proven to be highly specialized, herbivorous theropods. Therizinosaurs possessed large abdomens for processing plant food, and small heads with beaks and leaf-shaped teeth. Further study of maniraptoran theropods and their relationships showed that therizinosaurs were not
384-477: A family to the exclusion of Deinocheiridae (today, Deinocheirus is recognized as an ornithomimosaur ). Barsbold retained Segnosaurus and Erlikosaurus in the family Segnosauridae in 1983, and named the new genus Enigmosaurus based on the previously undetermined segnosaurian pelvis, which he placed in its own family, Enigmosauridae, within Segnosauria. Though the structure of the pelvis of Erlikosaurus
512-595: A phylogenetic analysis of coelurosauria. In 1999, paleontologist Xing Xu and colleagues described a small, basal therizinosauroid from China, Beipiaosaurus , which confirmed that the group belonged among the coelurosaurian theropods, and that similarities with prosauropods had evolved independently. They published the first ever cladogram showing the evolutionary relationships of Therizinosauria, and demonstrated that Beipiaosaurus had features of more basal theropods, coelurosaurs, and therizinosaurs. Sereno found Therizinosaurs to be basal Ornithomimosaurian theropods during
640-438: A tibial shaft; some ribs ; distal end of a humerus ; a tentative radius and the proximal end of an ulna . The femur however, was not found in association with the holotype individual, therefore it should be assigned to Therizinosauria incertae sedis ; the other remains might pertain to the holotype. A very large left femur, measuring 105 cm (1,050 mm) long, was labelled with the same specimen number too, however, it
768-514: A 1989 conference abstract about sauropodomorph interrelationships, paleontologist Paul Sereno also considered segnosaurs as prosauropods, based on skull features. In a 1990 review article , Barsbold and paleontologist Teresa Maryańska found Segnosauria to be a rare and aberrant group of saurischians, in an unresolved position among sauropodomorphs and theropods, probably closer to the former. They therefore listed them as Saurischia sedis mutabilis ("position subject to change"). Though they agreed
896-461: A 1999 paper by Paul Sereno suggests that theropods are characterized by traits such as an ectopterygoid fossa (a depression around the ectopterygoid bone), an intramandibular joint located within the lower jaw, and extreme internal cavitation within the bones. However, since taxa like Herrerasaurus may not be theropods, these traits may have been more widely distributed among early saurischians rather than being unique to theropods. Instead, taxa with
1024-537: A computed tomography scan and 3D reconstruction software. These finds are of evolutionary significance because they help document the emergence of the neurology of modern birds from that of earlier reptiles. An increase in the proportion of the brain occupied by the cerebrum seems to have occurred with the advent of the Coelurosauria and "continued throughout the evolution of maniraptorans and early birds." Studies show that theropods had very sensitive snouts. It
1152-557: A dinosaur. Both of these measures can only be calculated through fossilized bone and tissue , so regression analysis and extant animal growth rates as proxies are used to make predictions. Fossilized bones exhibit growth rings that appear as a result of growth or seasonal changes, which can be used to approximate age at the time of death. However, the amount of rings in a skeleton can vary from bone to bone, and old rings can also be lost at advanced age, so scientists need to properly control these two possibly confounding variables. Body mass
1280-533: A direct comparison between specimens is difficult to near impossible because there is no overlapping material (besides dorsal vertebrae) and the holotype of N. bohlini is apparently lost. Li and team disagree in that this species belong to Nanshiungosaurus and listed it as "Nanshiungosaurus" bohlini . Zanno in 2010 indicated that the anatomical traits that were originally used to characterize "N." bohlini are now known to be present in other therizinosaur taxa. Hartman with colleagues in 2019 recovered "N." bohlini as
1408-416: A group including the relatively derived theropod subgroups Ceratosauria and Tetanurae , and excluding coelophysoids . However, most later researchers have used it to denote a broader group. Neotheropoda was first defined as a clade by Paul Sereno in 1998 as Coelophysis plus modern birds , which includes almost all theropods except the most primitive species. Dilophosauridae was formerly considered
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#17327828640061536-457: A higher probability of being within the Theropoda may share more specific traits, such as a prominent promaxillary fenestra, cervical vertebrae with pleurocoels in the anterior part of the centrum leading to a more pneumatic neck, five or more sacral vertebrae, enlargement of the carpal bone, and a distally concave portion of the tibia, among a few other traits found throughout the skeleton. Like
1664-438: A manner similar to large mammals that lived later on, such as chalicotheres , ground sloths , great apes , and giant pandas . Skin impressions from Beipiaosaurus indicate that therizinosaurs were covered with a coat of primitive, down -like feathers similar to those seen in the compsognathid Sinosauropteryx , as well as longer, simpler, quill-like feathers that may have been used in display. Barsbold and Perle named
1792-464: A new infraorder, they did show similarities with them. Since the Erlikosaurus specimen lacked a pelvis, the authors were unsure if that of the undetermined segnosaurian could belong to it, in which case they would consider it part of a separate family. Though Erlikosaurus was difficult to compare directly to Segnosaurus due to the incompleteness of their remains, Perle stated in 1981 that there
1920-633: A partial lower jaw with teeth (IVPP V11579) from the Early Jurassic -aged Lufeng Formation in Yunnan , and concluded that this specimen represented the oldest known record of a coelurosaurian theropod. Based mainly on teeth morphology, they indicated therizinosaur affinities. The specimen was later described in depth in 2001 and used as the holotype specimen for the new genus and species Eshanosaurus deguchiianus , named by Xing and colleagues. The team reinforced therizinosaur relationships, arguing that
2048-480: A partial tibia and partial right pes (foot) largely lacking metatarsals. Dong referred it to the genus mainly based on similarities between the unguals of this specimen and those of C. tashuikouensis . Barsbold and Maryanska in 1990 considered C. zheziangensis as a tentative segnosaur (later known as therizinosaurs) based on its relatively short and robust pedal phalanges and enlarged, strongly curved unguals, mostly similar to Segnosaurus . As this taxon may lie outside
2176-476: A period of 50 million years, from an average of 163 kilograms (359 lb) down to 0.8 kilograms (1.8 lb), eventually evolving into over 11,000 species of modern birds . This was based on evidence that theropods were the only dinosaurs to get continuously smaller, and that their skeletons changed four times as fast as those of other dinosaur species. In order to estimate the growth rates of theropods, scientists need to calculate both age and body mass of
2304-658: A phylogenetic analysis and recovered it within Therizinosauroidea in a polytomy with Alxasaurus , Enigmosaurus and therizinosaurids. In 1997 Dong Zhiming and You Hailu named and described a supposed second species of Nanshiungosaurus , N. bohlini , based on specimen IVPP V 11116 found in 1992 at Early Cretaceous strata from the Zhonggou Formation , Xinminbao Group . It consists of 11 cervical and 5 dorsal vertebrae with some ribs . In order to contain both N. brevispinus and N. bohlini they coined
2432-416: A relationships between tooth size and skull length and also a comparison of the degree of wear of the teeth of non-avian theropods and modern lepidosaurs , it is concluded that theropods had lips that protected their teeth from the outside. Visually, the snouts of such theropods as Daspletosaurus had more similarities with lizards than crocodilians, which lack lips. Tyrannosaurus was for many decades
2560-554: A segnosaurian identity for Therizinosaurus . He also placed segnosauria within Phytodinosauria , a superorder that paleontologist Robert Bakker had created in 1985 to retain all plant-eating dinosaurs. In a 1986 study of the interrelationships of saurischian dinosaurs, paleontologist Jacques Gauthier concluded that segnosaurs were prosauropods. While he conceded they had similarities with ornithischians and theropods, he proposed these featured had evolved independently. In
2688-629: A segnosaurid, and reported a partial pelvis of an undetermined segnosaurian, both from the same formation as Segnosaurus . Combined, the specimens provided relatively complete data on this group; they were united by their opisthopubic pelvis, slender mandible, and the toothless front of their jaws. Barsbold and Perle stated that though some of their features resembled those of ornithischians and sauropods, these similarities were superficial, and were distinct when examined in detail. While they were essentially different from other theropods (perhaps due to diverging from them relatively early), and therefore warranted
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#17327828640062816-410: A shift in the use of the forearm, with greater flexibility at the shoulder allowing the arm to be raised towards the horizontal plane, and to even greater degrees in flying birds. However, in coelurosaurs, such as ornithomimosaurs and especially dromaeosaurids, the hand itself had lost most flexibility, with highly inflexible fingers. Dromaeosaurids and other maniraptorans also showed increased mobility at
2944-478: A side-branch of more advanced theropods, they may have been ancestral to all other theropods (which would make them a paraphyletic group). Neotheropoda (meaning "new theropods") is a clade that includes coelophysoids and more advanced theropod dinosaurs , and is the only group of theropods that survived the Triassic–Jurassic extinction event . Neotheropoda was named by R.T. Bakker in 1986 as
3072-425: A single unit with little flexibility. In theropods and prosauropods, the only way for the palm to face the ground would have been by lateral splaying of the entire forelimb, as in a bird raising its wing. In carnosaurs like Acrocanthosaurus , the hand itself retained a relatively high degree of flexibility, with mobile fingers. This was also true of more basal theropods, such as herrerasaurs . Coelurosaurs showed
3200-475: A small clade within Neotheropoda, but was later considered to be paraphyletic . By the Early Jurassic , all non-averostran neotheropods had gone extinct. Averostra (or "bird snouts") is a clade within Neotheropoda that includes most theropod dinosaurs , namely Ceratosauria and Tetanurae . It represents the only group of post-Early Jurassic theropods. One important diagnostic feature of Averostra
3328-400: A tetraradiate process. The holotype pelvis is in relatively good preservation, compromising the sacral vertebrae, partial ilium , right and left pubis and the left ischium . The pelvis is somewhat large as a whole and opisthopubic . The ilium is widely positioned and turned externally; it preserves a large cubic process in the posterodorsal area. Elongated pubic peduncles are present in
3456-562: A therizinosaurid in a clade joined by Segnosaurus and Nothronychus . Around 2005 partial therizinosaur material was collected from the Laijia Formation and later used to represent "Tiantaiosaurus sifengensis" (alternatively "Tiantaisaurus"), which is a currently unpuslihed and informal therizinosaur taxon. Qian and team in 2012 noted that a whole manuscript describing the taxon was written in 2007 but never officially published. In 1998 Zhao Xijin and Xu Xing briefly discovered
3584-665: A tooth from the Bathonian -aged Chipping Norton Limestone in England , to the Therizinosauroidea, making this the oldest record of Therizinosauroidea and also the first record of Therizinosauroidea in Europe . In 1979 Dong Zhiming named a new species of the megalosaurid Chilantaisaurus , C. zheziangensis , based on specimen ZhM V.001. This specimen was recovered in 1972 from the Tangshang Formation and consists of
3712-409: A well preserved pelvic girdle with other postcrania. The generic name , Enigmosaurus , was stated to be derived from Greek αίνιγμα ( aínigma , meaning enigma) and σαῦρος ( sauros , meaning lizard), in reference to the aberratic and unusual shape of its pelvis. The specific name , mongoliensis , refers to the country of its discovery, Mongolia. Some therizinosaur fossil findings at
3840-406: A wide variety of tasks (see below). In modern birds, the body is typically held in a somewhat upright position, with the upper leg (femur) held parallel to the spine and with the forward force of locomotion generated at the knee. Scientists are not certain how far back in the theropod family tree this type of posture and locomotion extends. Non-avian theropods were first recognized as bipedal during
3968-639: Is a therizinosaur. In 2012 the Mongolian Academy of Sciences recovered a partial theropod specimen from the Bayan Shireh Formation at the Urlibe Khudak (also Ulribe Khuduk) locality. The specimen was in a 2015 abstract by Yoshitsugu Kobayashi and team briefly described and identified as a new therizinosaur taxon distinct from the concurring Enigmosaurus , Erlikosaurus and Segnosaurus . The Urlibe Khudak therizinosaur
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4096-468: Is also believed to have also been different among different families. The spinosaurids could have used their powerful forelimbs to hold fish. Some small maniraptorans such as scansoriopterygids are believed to have used their forelimbs to climb in trees . The wings of modern birds are used primarily for flight, though they are adapted for other purposes in certain groups. For example, aquatic birds such as penguins use their wings as flippers. Contrary to
4224-487: Is an extant dinosaur clade that is characterized by hollow bones and three toes and claws on each limb. Theropods are generally classed as a group of saurischian dinosaurs. They were ancestrally carnivorous , although a number of theropod groups evolved to become herbivores and omnivores . Theropods first appeared during the Carnian age of the late Triassic period 231.4 million years ago ( Ma ) and included
4352-410: Is defined as Alxasaurus , Enigmosaurus , Erlikosaurus , Nanshiungosaurus , Segnosaurus , Therizinosaurus , and all taxa closer to them than to oviraptorosaurs , ornithomimids , and troodontids . Paul Sereno , in 2005, modified this definition to the most inclusive clade containing Therizinosaurus but not Ornithomimus , Oviraptor , Shuvuuia , Tyrannosaurus , or Troodon . When it
4480-525: Is harder to determine as bone mass only represents a small proportion of the total body mass of animals. One method is to measure the circumference of the femur, which in non-avian theropod dinosaurs has been shown to be a relatively proportional to quadrupedal mammals, and use this measurement as a function of body weight, as the proportions of long bones like the femur grow proportionately with body mass. The method of using extant animal bone proportion to body mass ratios to make predictions about extinct animals
4608-470: Is known as the extant-scaling (ES) approach. A second method, known as the volumetric-density (VD) approach, uses full-scale models of skeletons to make inferences about potential mass. The ES approach is better for wide-range studies including many specimens and doesn't require as much of a complete skeleton as the VD approach, but the VD approach allows scientists to better answer more physiological questions about
4736-491: Is most notably for its manual morphology which consist of only two fingers ( didactyly ), in a similar manner to tyrannosaurids . Such trait makes it the only known two-fingered therizinosaur. Therizinosaurs spanned a large range of sizes, from the smaller Beipiaosaurus (2.2 m (7.2 ft) long) and Jianchangosaurus (2 m (6.6 ft) long) to the large-sized 6–7 m (20–23 ft) long Segnosaurus and Suzhousaurus . Therizinosaurus itself, obtained
4864-463: Is recovered as a derived therizinosauroid. Falcarius [REDACTED] Jianchangosaurus [REDACTED] Beipiaosaurus [REDACTED] " Chilantaisaurus " zheziangensis Enigmosaurus [REDACTED] Alxasaurus Therizinosauridae [REDACTED] The remains of Enigmosaurus were found in sediments that were deposited during the Late Cretaceous period on
4992-512: Is suggested they might have been used for temperature detection, feeding behavior, and wave detection. Shortened forelimbs in relation to hind legs was a common trait among theropods, most notably in the abelisaurids (such as Carnotaurus ) and the tyrannosaurids (such as Tyrannosaurus ). This trait was, however, not universal: spinosaurids had well developed forelimbs, as did many coelurosaurs. The relatively robust forelimbs of one genus, Xuanhanosaurus , led D. Zhiming to suggest that
5120-507: Is the common ostrich , up to 2.74 m (9 ft) tall and weighing between 90 and 130 kg (200 - 290 lb). The smallest non-avialan theropod known from adult specimens is the troodontid Anchiornis huxleyi , at 110 grams in weight and 34 centimeters (1 ft) in length. When modern birds are included, the bee hummingbird ( Mellisuga helenae ) is smallest at 1.9 g and 5.5 cm (2.2 in) long. Recent theories propose that theropod body size shrank continuously over
5248-584: Is the absence of the fifth metacarpal. Other saurischians retained this bone, albeit in a significantly reduced form. The somewhat more advanced ceratosaurs (including Ceratosaurus and Carnotaurus ) appeared during the Early Jurassic and continued through to the Late Jurassic in Laurasia . They competed alongside their more anatomically advanced tetanuran relatives and—in the form of
Therizinosauria - Misplaced Pages Continue
5376-860: Is the recently performed phylogenetic analysis performed by Hartman et al. 2019 using the data provided by Zanno in 2010: Falcarius [REDACTED] Jianchangosaurus [REDACTED] Beipiaosaurus [REDACTED] "Chilantaisaurus" zheziangensis Enigmosaurus [REDACTED] Alxasaurus Suzhousaurus [REDACTED] Neimongosaurus [REDACTED] Therizinosaurus [REDACTED] Erliansaurus [REDACTED] Nanchao embryos [REDACTED] Nanshiungosaurus [REDACTED] Segnosaurus [REDACTED] AMNH 6368 [REDACTED] Theropoda Theropoda ( / θ ɪəˈr ɒ p ə d ə / ; from ancient Greek θηρίο- ποδός [ θηρίον , ( therion ) "wild beast"; πούς , ποδός ( pous, podos ) "foot"]) whose members are known as theropods ,
5504-542: Is unknown and distinguishing traits between them were absent; if proven, this would make Enigmosaurus a junior synonym of Erlikosaurus . However, the Enigmosaurus pelvis doesn't resemble that of Segnosaurus as would be expected for the connection with Erlikosaurus , and there is a huge size difference. In addition, both genera are known from different strata (lower and upper), and they are considered to be distinct animals by most authors. Enigmosaurus
5632-449: Is used to signify groups with no living members. The following family tree illustrates a synthesis of the relationships of the major theropod groups based on various studies conducted in the 2010s. † Herrerasauridae [REDACTED] † Eoraptor † Eodromaeus † Daemonosaurus Enigmosaurus Enigmosaurus (meaning "Enigma lizard" or "Enigmatic lizard") is a genus of therizinosauroid that lived in Asia during
5760-416: Is very particular compared to other therizinosaur relatives, featuring areas of bone resorption and bone remodeling on the ilium. These specific traits may indicate the advanced age of the individual, if true, the fusion of the obturator process and pubic body could be discarded as an authentic autapomorphy for the species. Zanno noted that more analyses are required to settle this enigma. Enigmosaurus
5888-605: The Allosauroidea (the diverse carcharodontosaurs ) and the Coelurosauria (a very large and diverse dinosaur group including the birds). Thus, during the late Jurassic, there were no fewer than four distinct lineages of theropods—ceratosaurs, megalosaurs, allosaurs, and coelurosaurs—preying on the abundance of small and large herbivorous dinosaurs. All four groups survived into the Cretaceous, and three of those—the ceratosaurs, coelurosaurs, and allosaurs—survived to end of
6016-551: The Bayan Shireh Formation , Khara Khutul locality, about 95.9 ± 6.0 million to 89.6 ± 4.0 million years ago, Cenomanian - Santonian ages. Being a therizinosaur, it was likely a slow herbivore and/or omnivore , as suggested by most authors all over the time. The biodiversity across the formation was characterized by therizinosaurs, as seen on the remains of Enigmosaurus , Erlikosaurus and Segnosaurus . The holotype location, Khara Khutul, has also yielded
6144-671: The Coelophysoidea . The coelophysoids were a group of widely distributed, lightly built and potentially gregarious animals. They included small hunters like Coelophysis and Camposaurus . These successful animals continued from the Late Carnian (early Late Triassic) through to the Toarcian (late Early Jurassic ). Although in the early cladistic classifications they were included under the Ceratosauria and considered
6272-496: The Iren Dabasu Formation were first thought to be referable to Enigmosaurus . Although it is commonly known from the pelvis, several remains not mentioned in the original description of the holotype were labelled under the same specimen number (IGM 100/84). These elements are in poor condition compared to the pelvis, and they were not measured and illustrated: proximal end of a femur ; large femoral shaft, might be
6400-412: The Late Cretaceous period . It was a medium-sized, ground-dwelling, bipedal herbivore that represents the third therizinosaur taxon from the Bayan Shireh Formation , although it is known from the lower part. The genus is monotypic , including only the type species E. mongoliensis , known from a well preserved pelvis and other tentative body remains. The holotype , IGM 100/84 , was discovered at
6528-589: The abelisaur lineage—lasted to the end of the Cretaceous in Gondwana . The Tetanurae are more specialised again than the ceratosaurs. They are subdivided into the basal Megalosauroidea (alternately Spinosauroidea ) and the more derived Avetheropoda . Megalosauridae were primarily Middle Jurassic to Early Cretaceous predators, and their spinosaurid relatives' remains are mostly from Early and Middle Cretaceous rocks. Avetheropoda, as their name indicates, were more closely related to birds and are again divided into
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#17327828640066656-481: The clade Tetanurae for one branch of a basic theropod split with another group, the Ceratosauria. As more information about the link between dinosaurs and birds came to light, the more bird-like theropods were grouped in the clade Maniraptora (also named by Gauthier in 1986 ). These new developments also came with a recognition among most scientists that birds arose directly from maniraptoran theropods and, on
6784-742: The coelurosaurs , feathers may have been confined to the young, smaller species, or limited parts of the animal. Many larger theropods had skin covered in small, bumpy scales. In some species, these were interspersed with larger scales with bony cores, or osteoderms . This type of skin is best known in the ceratosaur Carnotaurus , which has been preserved with extensive skin impressions. The coelurosaur lineages most distant from birds had feathers that were relatively short and composed of simple, possibly branching filaments. Simple filaments are also seen in therizinosaurs, which also possessed large, stiffened "quill"-like feathers. More fully feathered theropods, such as dromaeosaurids , usually retain scales only on
6912-524: The cranium and forelimb, with injuries occurring in about equal frequency at each site. Most pathologies preserved in theropod fossils are the remains of injuries like fractures, pits, and punctures, often likely originating with bites. Some theropod paleopathologies seem to be evidence of infections , which tended to be confined only to small regions of the animal's body. Evidence for congenital malformities have also been found in theropod remains. Such discoveries can provide information useful for understanding
7040-630: The furcula (wishbone), pneumatized bones, brooding of the eggs , and (in coelurosaurs, at least) feathers . O. C. Marsh coined the name Theropoda (meaning "beast feet") in 1881. Marsh initially named Theropoda as a suborder to include the family Allosauridae , but later expanded its scope, re-ranking it as an order to include a wide array of "carnivorous" dinosaur families, including Megalosauridae , Compsognathidae , Ornithomimidae , Plateosauridae and Anchisauridae (now known to be herbivorous sauropodomorphs ) and Hallopodidae (subsequently revealed as relatives of crocodilians). Due to
7168-455: The spinosaurids ) appear to have specialized in catching fish. Diet is largely deduced by the tooth morphology , tooth marks on bones of the prey, and gut contents. Some theropods, such as Baryonyx , Lourinhanosaurus , ornithomimosaurs, and birds, are known to use gastroliths , or gizzard-stones. The majority of theropod teeth are blade-like, with serration on the edges, called ziphodont. Others are pachydont or folidont depending on
7296-567: The "bird-hipped" ornithischians . Among the most striking characteristics of therizinosaurs are the enormous claws on their hands, which reached lengths of around one meter in Therizinosaurus . The unusual range of motion in therizinosaur forelimbs, which allowed them to reach forward to a degree other theropods could not achieve, also supports the idea that they were mainly herbivorous. Therizinosaurs may have used their long reach and strongly curved claws to grasp and shear leafy branches, in
7424-480: The 19th century, before their relationship to birds was widely accepted. During this period, theropods such as carnosaurs and tyrannosaurids were thought to have walked with vertical femurs and spines in an upright, nearly erect posture, using their long, muscular tails as additional support in a kangaroo-like tripodal stance. Beginning in the 1970s, biomechanical studies of extinct giant theropods cast doubt on this interpretation. Studies of limb bone articulation and
7552-469: The Early Cretaceous. A few palaeontologists, such as Gregory S. Paul , have suggested that some or all of these advanced theropods were actually descended from flying dinosaurs or proto-birds like Archaeopteryx that lost the ability to fly and returned to a terrestrial habitat. The evolution of birds from other theropod dinosaurs has also been reported, with some of the linking features being
7680-539: The Khara Khutul locality in the Bayan Shireh Formation (sometimes called Baynshire Formation or the Baynshirenskaya Svita), southeastern Mongolia , dating from the Late Cretaceous period, and first reported in 1979 on a pelvic comparison with other theropod dinosaurs. At the time, little was known about therizinosaurs. In 1980, it was mentioned again, this time in the new infraorder created by
7808-458: The Mongolian paleontologists Rinchen Barsbold and Altangerel Perle : Segnosauria . Nicknamed as the "Dinosaur from Khara Khutul", it was shortly described and included into the Segnosauria. Three years later, the type species , Enigmosaurus mongoliensis , was named and described in 1983 by Barsbold. The preserved elements consist of a partial skeleton, lacking the skull, that includes
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#17327828640067936-527: The Nanshiungosauridae family. Dong and Yu presented no clear evidence regarding the assignment of this new species to Nanshiungosaurus . Li and colleagues in their 2007 description of Suzhousaurus pointed out that N. bohlini might be synonymous with the former, as both are found in the same geological group and also incompletely known. As per terms of taxonomic priority , the species name would be Suzhousaurus bohlini . However, they noted that
8064-681: The Order Saurischia into two suborders, Theropoda and Sauropoda. This basic division has survived into modern palaeontology, with the exception of, again, the Prosauropoda, which Romer included as an infraorder of theropods. Romer also maintained a division between Coelurosauria and Carnosauria (which he also ranked as infraorders). This dichotomy was upset by the discovery of Deinonychus and Deinocheirus in 1969, neither of which could be classified easily as "carnosaurs" or "coelurosaurs". In light of these and other discoveries, by
8192-466: The Tetanurae and Ceratosauria. While some used to consider coelophysoids and ceratosaurs to be within the same group due to features such as a fused hip, later studies showed that it is more likely that these were features ancestral to neotheropods and were lost in basal tetanurans. Averostrans and their close relatives are united via the complete loss of any digit V remnants, fewer teeth in the maxilla,
8320-515: The abandonment of ranks in cladistic classification, with the re-evaluation of birds as a subset of theropod dinosaurs that survived the Mesozoic extinctions and lived into the present. The following is a simplified classification of theropod groups based on their evolutionary relationships, and organized based on the list of Mesozoic dinosaur species provided by Holtz. A more detailed version can be found at dinosaur classification . The dagger (†)
8448-546: The animal might have been quadrupedal. However, this is no longer thought to be likely. The hands are also very different among the different groups. The most common form among non-avian theropods is an appendage consisting of three fingers; the digits I, II and III (or possibly II, III and IV ), with sharp claws. Some basal theropods, like most Ceratosaurians , had four digits, and also a reduced metacarpal V (e.g. Dilophosaurus ). The majority of tetanurans had three, but some had even fewer. The forelimbs' scope of use
8576-459: The animal, such as locomotion and center of gravity. The current consensus is that non-avian theropods didn't exhibit a group wide growth rate, but instead had varied rates depending on their size. However, all non-avian theropods had faster growth rates than extant reptiles, even when modern reptiles are scaled up to the large size of some non-avian theropods. As body mass increases, the relative growth rate also increases. This trend may be due to
8704-484: The avian theropods (birds). However, discoveries in the late 20th and early 21st centuries showed that a variety of diets existed even in more basal lineages. All early finds of theropod fossils showed them to be primarily carnivorous . Fossilized specimens of early theropods known to scientists in the 19th and early 20th centuries all possessed sharp teeth with serrated edges for cutting flesh, and some specimens even showed direct evidence of predatory behavior. For example,
8832-538: The borders" of this group, but opted to retain them within Theropoda. In the same year, Barsbold stated that the segnosaurian pelvis deviated strongly from the theropod norm, and found the configuration of their ilia generally similar to those of sauropods . Paleontologist Gregory S. Paul concluded in 1984 that segnosaurs did not possess any theropodan features, but were instead derived, late-surviving Cretaceous prosauropods with adaptations similar to those of ornithischians. He found segnosaurs similar to prosauropods in
8960-483: The common descent of these groups as support for the idea that dinosaurs were a monophyletic (natural) group, which was contested by some paleontologists at the time (who instead thought different dinosaurs groups evolved independently from thecodonts ). Paleontologist David B. Norman considered Paul's idea a contentious claim "bound to provoke much argument" in 1985. In 1988, Paul maintained that segnosaurs were late surviving ornithischian-like prosauropods, and proposed
9088-413: The contemporary Segnosaurus and an unnamed velociraptorine . Most of the remaining paleofauna from this formation is known from Upper strata, whereas Enigmosaurus is known from Lower strata. At the locality, diverse paleoflora has been discovered, such as Cornaceae reported with Bothrocaryum gobience and Nyssoidea mongolica as fine representatives. Numerous fossil fruit findings at
9216-399: The detailed morphology of its limbs linked it to Therizinosaurus and segnosaurs. Since it preserved both fore and hindlimbs, Alxasaurus showed that Perle's assignment of segnosaurian hindlimbs to Therizinosaurus was probably correct. Russell and Dong therefore proposed that Segnosauridae was a junior synonym of Therizinosauridae (since the latter name was older), with Alxasaurus being
9344-499: The different parts of theropod anatomy. The most common sites of preserved injury and disease in theropod dinosaurs are the ribs and tail vertebrae . Despite being abundant in ribs and vertebrae, injuries seem to be "absent... or very rare" on the bodies' primary weight supporting bones like the sacrum , femur , and tibia . The lack of preserved injuries in these bones suggests that they were selected by evolution for resistance to breakage. The least common sites of preserved injury are
9472-421: The early sauropodomorphs, the second digit in a theropod's hand is enlarged. Theropods also have a very well developed ball and socket joint near their neck and head. Most theropods belong to the clade Neotheropoda, characterized by the reduction of several foot bones, thus leaving three toed footprints on the ground when they walk (tridactyl feet). Digit V was reduced to a remnant early in theropod evolution and
9600-619: The evolutionary history of the processes of biological development. Unusual fusions in cranial elements or asymmetries in the same are probably evidence that one is examining the fossils of an extremely old individual rather than a diseased one. The trackway of a swimming theropod, the first in China of the ichnogenus named Characichnos , was discovered at the Feitianshan Formation in Sichuan. These new swim tracks support
9728-413: The feet. Some species may have mixed feathers elsewhere on the body as well. Scansoriopteryx preserved scales near the underside of the tail, and Juravenator may have been predominantly scaly with some simple filaments interspersed. On the other hand, some theropods were completely covered with feathers, such as the troodontid Anchiornis , which even had feathers on the feet and toes. Based on
9856-470: The first known dromaeosaurid ( Dromaeosaurus albertensis ) in 1922, W. D. Matthew and Barnum Brown became the first paleontologists to exclude prosauropods from the carnivorous dinosaurs, and attempted to revive the name "Goniopoda" for that group, but other scientists did not accept either of these suggestions. In 1956, "Theropoda" came back into use—as a taxon containing the carnivorous dinosaurs and their descendants—when Alfred Romer re-classified
9984-413: The genus Chilantaisaurus , they listed this species as "Chilantaisaurus" zheziangensis . Although Glut (1997) stated this specimen may have been based on part of the holotype of Nanshiungosaurus brevispinus (based on a pers. comm from Dong to Molnar in 1984), Dong in 1979 described both taxa from largely different formations and localities. Zanno in 2010 argued that the notorious side to side compression of
10112-402: The group Oviraptorosauria (since they found Maniraptora , the conventional grouping of these, invalid, and the higher level taxonomy of theropods was in flux at the time). The synonymy of Segnosauridae with Therizinosauridae was accepted by Perle himself and co-authors of a redescription of the holotype skull of Erlikosaurus in 1994, and they considered therizinosaurs maniraptoran theropods,
10240-444: The group Segnosauria as an infraorder of Theropoda in 1980. Dong Zhiming went further, placing the segnosaurs in their own order, Segnosaurischia . This name has been abandoned since the discovery that segnosaurs are a specialized group within the suborder Theropoda. Clark et al. 2004 considered Segnosaurischia a synonym of Therizinosauroidea. The clade Therizinosauria was first coined by Dale Russell in 1997—effectively replacing
10368-522: The group that also includes modern birds (since they did find Maniraptora to be valid through their analysis). They also discussed the previous ornithischian and sauropod hypotheses for therizinosaur affinities in detail and demonstrated various faults with them. Palaeontologist Lev Alexandrovich Nessov rejected that therizinosaurs were theropods in 1995, and instead considered them a distinct group within saurischia. In 1996, paleontologist Thomas R. Holtz Jr. found therizinosaurs to group with oviraptorosaurs in
10496-542: The group were also still uncertain by 2010, when Zanno conducted the most detailed phylogenetic analysis of the Therizinosauria until that point. She cited the inaccessibility, damage, potential loss of holotype specimens, scarcity of cranial remains, and fragmentary specimens with few overlapping elements as the most significant obstacles to resolving the evolutionary relationships within the group. Wills, Underwood & Barrett (2023) assigned specimen GLCRM G167-32,
10624-438: The hindlimbs assigned to Therizinosaurus in 1982 were segnosaurian, they did not consider this justification for Therizinosaurus itself being a segnosaur, since it was only known from forelimbs. In 1993, paleontologists Dale A. Russell and Dong Zhi-Ming described the new genus Alxasaurus from China, at the time the most complete large theropod from its time and place. While it was similar to prosauropods in some respects,
10752-621: The hypothesis that theropods were adapted to swimming and capable of traversing moderately deep water. Dinosaur swim tracks are considered to be rare trace fossils, and are among a class of vertebrate swim tracks that also include those of pterosaurs and crocodylomorphs . The study described and analyzed four complete natural molds of theropod foot prints that are now stored at the Huaxia Dinosaur Tracks Research and Development Center (HDT). These dinosaur footprints were in fact claw marks, which suggest that this theropod
10880-476: The ilium; the ischial peduncles are more reduced though. The distal end of the pubis is elongated, recurved and stocky. The ischium, is slightly shorter than the pubis and parallel to it, with a narrow shaft. The obturator process on the front edge of the ischium is horizontally elongated and low. Open edges are appreciable on the large trochanteric fossa . Apparently, the sacrum preserves six vertebrae, with elongated transverse processes . For instance, its pelvis
11008-422: The knee was normally strongly flexed in all theropods while walking, even giants like the tyrannosaurids. It is likely that a wide range of body postures, stances, and gaits existed in the many extinct theropod groups. Although rare, complete casts of theropod endocrania are known from fossils. Theropod endocrania can also be reconstructed from preserved brain cases without damaging valuable specimens by using
11136-414: The largest known theropod and best known to the general public. Since its discovery, however, a number of other giant carnivorous dinosaurs have been described, including Spinosaurus , Carcharodontosaurus , and Giganotosaurus . The original Spinosaurus specimens (as well as newer fossils described in 2006) support the idea that Spinosaurus is longer than Tyrannosaurus , showing that Spinosaurus
11264-469: The largest living land animal today, the African elephant , which is characterized by a rapid period of growth until maturity, subsequently followed by slowing growth in adulthood. As a hugely diverse group of animals, the posture adopted by theropods likely varied considerably between various lineages through time. All known theropods are bipedal , with the forelimbs reduced in length and specialized for
11392-457: The late 1970s Rinchen Barsbold had created a new series of theropod infraorders: Coelurosauria, Deinonychosauria , Oviraptorosauria , Carnosauria, Ornithomimosauria, and Deinocheirosauria . With the advent of cladistics and phylogenetic nomenclature in the 1980s, and their development in the 1990s and 2000s, a clearer picture of theropod relationships began to emerge. Jacques Gauthier named several major theropod groups in 1986, including
11520-459: The majority of large terrestrial carnivores from the Early Jurassic until at least the close of the Cretaceous , about 66 Ma. In the Jurassic , birds evolved from small specialized coelurosaurian theropods, and are today represented by about 11,000 living species. Various synapomorphies for Theropoda have been proposed based on which taxa are included in the group. For example,
11648-748: The morphology of their snout, mandible, and hindfoot, and to ornithischians in their cheek, palate, pubis, and ankle, and similar to early dinosaurs in other respects. He proposed that ornithischians were descended from prosauropods, and that the segnosaurs were an intermediate relict of this transition, which supposedly took place during the Triassic period . In this way, he considered segnosaurians to be to herbivorous dinosaurs what monotremes are to mammals. He did not rule out that segnosaurs could be derived from theropods, or that segnosaurs, prosauropods and ornithischians were each independently derived from early dinosaurs, but found these options unlikely. He considered
11776-523: The most completely known representative so far, providing a better understanding of the group. They also named the new higher taxonomic rank Therizinosauroidea to contain Alxasaurus and Therizinosauridae (since the new genus was somewhat different from its relatives), which they placed in the group Tetanurae within Theropoda. They considered therizinosaurs most closely related to ornithomimids, troodontids, and oviraptorids, which they placed together in
11904-404: The movement of the tooth row further down the maxilla and a lacrimal fenestra. Averostrans also share features in their hips and teeth. Theropods exhibit a wide range of diets, from insectivores to herbivores and carnivores. Strict carnivory has always been considered the ancestral diet for theropods as a group, and a wider variety of diets was historically considered a characteristic exclusive to
12032-868: The name Therizinosauria to remain in use for the larger group comprising all therizinosaurs. This definition was followed by Sereno (2005), Zanno et al. (2009) and Zanno (2010), though other subsequent studies, such as Senter (2007, 2012) have continued to use Therizinosauroidea for the therizinosaur "total group". The cladogram below follows the extensive phylogenetic analysis of the Therizinosauria by Lindsay E. Zanno in 2010. Falcarius [REDACTED] Beipiaosaurus [REDACTED] Alxasaurus Erliansaurus [REDACTED] Neimongosaurus [REDACTED] Enigmosaurus [REDACTED] Suzhousaurus [REDACTED] Nothronychus [REDACTED] Nanshiungosaurus [REDACTED] Segnosaurus [REDACTED] Erlikosaurus [REDACTED] Therizinosaurus [REDACTED] Below
12160-660: The need to reach the size required for reproductive maturity . For example, one of the smallest known theropods was Microraptor zhaoianus , which had a body mass of 200 grams, grew at a rate of approximately 0.33 grams per day. A comparable reptile of the same size grows at half of this rate. The growth rates of medium-sized non-avian theropods (100–1000 kg) approximated those of precocial birds, which are much slower than altricial birds. Large theropods (1500–3500 kg) grew even faster, similar to rates displayed by eutherian mammals. The largest non-avian theropods, like Tyrannosaurus rex had similar growth dynamics to
12288-553: The older name Segnosauria, which has not yet been defined as a clade—to contain all therizinosaurian dinosaurs. The superfamily Therizinosauroidea was first coined in 1993 as a superfamily with no phylogenetic definition. The family Therizinosauridae had been established by Maleev in 1954 to include only the bizarre, giant-clawed theropod Therizinosaurus . Subsequent analyses have proven this family to be more diverse and synonymous with Segnosauridae. The following taxonomy follows Zanno 2010, unless otherwise noted. Therizinosauria
12416-560: The oldest known bird, Archaeopteryx ), the bird-like troodontids and oviraptorosaurs, the ornithomimosaurs (or "ostrich Dinosaurs"), the strange giant-clawed herbivorous therizinosaurs, and the avialans, which include modern birds and is the only dinosaur lineage to survive the Cretaceous–Paleogene extinction event . While the roots of these various groups are found in the Middle Jurassic, they only became abundant during
12544-407: The only early members of this group to abandon carnivory. Several other lineages of early maniraptorans show adaptations for an omnivorous diet, including seed-eating (some troodontids ) and insect-eating (many avialans and alvarezsaurs ). Oviraptorosaurs , ornithomimosaurs and advanced troodontids were likely omnivorous as well, and some early theropods (such as Masiakasaurus knopfleri and
12672-418: The palms faced the ground or backwards towards the legs. In humans, pronation is achieved by motion of the radius relative to the ulna (the two bones of the forearm). In saurischian dinosaurs, however, the end of the radius near the elbow was actually locked into a groove of the ulna, preventing any movement. Movement at the wrist was also limited in many species, forcing the entire forearm and hand to move as
12800-400: The past considered the herrerasaurians to be members of Theropoda, while other theorized the group to be basal saurischians, and may even have evolved prior to the saurischian-ornithischian split. Cladistic analysis following the discovery of Tawa , another Triassic dinosaur, suggests the herrerasaurs likely were early theropods. The earliest and most primitive unambiguous theropods are
12928-541: The period, where they were geographically separate, the ceratosaurs and allosaurs in Gondwana, and the coelurosaurs in Laurasia. Of all the theropod groups, the coelurosaurs were by far the most diverse. Some coelurosaur groups that flourished during the Cretaceous were the tyrannosaurids (including Tyrannosaurus ), the dromaeosaurids (including Velociraptor and Deinonychus , which are remarkably similar in form to
13056-439: The relative absence of trackway evidence for tail dragging suggested that, when walking, the giant, long-tailed theropods would have adopted a more horizontal posture with the tail held parallel to the ground. However, the orientation of the legs in these species while walking remains controversial. Some studies support a traditional vertically oriented femur, at least in the largest long-tailed theropods, while others suggest that
13184-737: The representative genus, Therizinosaurus , is derived from the Greek θερίζω ( therízō , 'to reap' or 'scythe') and σαῦρος ( saûros , 'lizard'). The older representative, Segnosaurus , is derived from the Latin sēgnis ('slow') and the Greek σαῦρος . Therizinosaurs were long considered an enigmatic group, whose mosaic of features resembling those of various different dinosaur groups, and scarcity of their fossils, led to controversy over their evolutionary relationships for decades after their initial discovery. The first genus, Therizinosaurus ,
13312-401: The revised diagnosis by Zanno et al. 2010 , there are even more specific traits for Enigmosaurus that were not pointed out/analyzed before: prominent cranial and caudal processes on the dorsoventrally somewhat flattened pubic boot; the pubic feet are fused, being medially elongated, a medial expansion forms a V-shaped structure; the medial fusion of the obturator process and pubic body, forms
13440-470: The same rank, possibly at the level of infraorder within Saurischia (one of the two main divisions of dinosaurs, the other being Ornithischia ). In 1980, Barsbold and Perle named the new theropod infraorder Segnosauria, containing only Segnosauridae. In the same article, they named the new genus Erlikosaurus (known from a well-preserved skull and partial skeleton) which they tentatively considered
13568-468: The scope of Marsh's Order Theropoda, it came to replace a previous taxonomic group that Marsh's rival E. D. Cope had created in 1866 for the carnivorous dinosaurs: Goniopoda ("angled feet"). By the early 20th century, some palaeontologists, such as Friedrich von Huene , no longer considered carnivorous dinosaurs to have formed a natural group. Huene abandoned the name "Theropoda", instead using Harry Seeley 's Order Saurischia , which Huene divided into
13696-787: The shape of the tooth or denticles . The morphology of the teeth is distinct enough to tell the major families apart, which indicate different diet strategies. An investigation in July 2015 discovered that what appeared to be "cracks" in their teeth were actually folds that helped to prevent tooth breakage by strengthening individual serrations as they attacked their prey. The folds helped the teeth stay in place longer, especially as theropods evolved into larger sizes and had more force in their bite. Mesozoic theropods were also very diverse in terms of skin texture and covering. Feathers or feather-like structures (filaments) are attested in most lineages of theropods (see feathered dinosaur ). However, outside
13824-496: The suborders Coelurosauria and Pachypodosauria . Huene placed most of the small theropod groups into Coelurosauria, and the large theropods and prosauropods into Pachypodosauria, which he considered ancestral to the Sauropoda (prosauropods were still thought of as carnivorous at that time, owing to the incorrect association of rauisuchian skulls and teeth with prosauropod bodies, in animals such as Teratosaurus ). Describing
13952-415: The teeth morphology of Eshanosaurus can be differentiated from sauropodomorphs . In the same 2001 however, James I. Kirkland and Douglas G. Wolfe noted that the holotype of Eshanosaurus preserves traits only seen in sauropodomorphs. Paul M. Barrett in 2009 examined the specimen in detail, noting six features shared with therizinosaurs but not exhibited by prosauropods, agreeing in that Eshanosaurus
14080-476: The theropod dinosaurs were the carnivorous Eodromaeus and, possibly, the herrerasaurids of Argentina . The herrerasaurs existed during the early late Triassic (Late Carnian to Early Norian ). They were found in North America and South America and possibly also India and Southern Africa. The herrerasaurs were characterised by a mosaic of primitive and advanced features. Some paleontologists have in
14208-483: The theropod families Deinocheiridae and Therizinosauridae (then only known from the genera Deinocheirus and Therizinosaurus , both mainly represented by large forelimbs found in Mongolia) by features of their humeri and hand claws. Later in 1979, Barsbold and Perle found the pelvic features of segnosaurids and dromaeosaurids so different from those of "true" theropods that they should be separated into three taxa of
14336-518: The top dimensions of the group, growing up to 10 m (33 ft) long and weighing over 5 t (11,000 lb), dimensions that make the genus among the largest-known theropods . Therizinosaurs had a very distinctive, often confusing set of characteristics. Their long necks, wide torsos, and hind feet with four toes used in walking resembled those of basal sauropodomorph dinosaurs. Their unique hip bones, which pointed backwards and were partially fused together, initially reminded paleontologists of
14464-406: The unguals reflect therizinosaur affinities, although examinations to the preserved tibia are required for further conclusions. In 2012 Mai-Ping Qian and colleagues placed "C". zheziangensis in the family Therizinosauridae based on its pes morphology, which is consistent to other therizinosaurids. They also illustrated most of the preserved pes. Hartman with team in 2019 added "C". zheziangensis to
14592-408: The way theropods have often been reconstructed in art and the popular media, the range of motion of theropod forelimbs was severely limited, especially compared with the forelimb dexterity of humans and other primates . Most notably, theropods and other bipedal saurischian dinosaurs (including the bipedal prosauropods ) could not pronate their hands—that is, they could not rotate the forearm so that
14720-603: The wrist not seen in other theropods, thanks to the presence of a specialized half-moon shaped wrist bone (the semi-lunate carpal) that allowed the whole hand to fold backward towards the forearm in the manner of modern birds. In 2001, Ralph E. Molnar published a survey of pathologies in theropod dinosaur bone. He found pathological features in 21 genera from 10 families. Pathologies were found in theropods of all body size although they were less common in fossils of small theropods, although this may be an artifact of preservation. They are very widely represented throughout
14848-486: The year 1999. By the early 21st century, many more therizinosaur taxa had been discovered, including outside Asia (the first being Nothronychus from North America), as well as various basal taxa that helped understanding of the early evolution of the group (such as Falcarius , also from North America). Therizinosaurs were not considered as rare or aberrant anymore, but more diverse than previously thought (including in size), and their classification as maniraptoran theropods
14976-402: Was a relatively large-bodied therizinosaur, with an estimated length of 5 m (16 ft) and a weight between 454 to 907 kg (1,001 to 2,000 lb). As noted by Barsbold in the original description of Enigmosaurus , it can recognised by the following characteristics: the pubis and ischium are short; elongated margin in the anterior presymphyseal region of the distal pubis. However, in
15104-635: Was by the describers assigned to a separate Enigmosauridae (now obsolete) due to its aberrant pelvis, but later considered a member of the Segnosauridae which are today called the Therizinosauridae . Lindsay Zanno in 2010 recovered a position more basal in the Therizinosauroidea . Below are the results of the recently performed phylogenetic analysis of the Therizinosauria by Hartman et al. 2019 , in which Enigmosaurus
15232-479: Was first defined by Zhang et al. in 2001, as the clade containing all theropods more closely related to Therizinosaurus than to birds. This definition, however, defines the same group as the pre-existing Therizinosauria. An alternate definition was given by Clark in 2004 (as the last common ancestor of Therizinosaurus and Beipiaosaurus and all its descendants), comprising a narrower group that excludes more primitive therizinosaurs, such as Falcarius , and allows
15360-471: Was generally accepted. The placement of Therizinosauria within Maniraptora continued to be unclear; in 2007, paleontologist Alan H. Turner and colleagues found them to group with oviraptorosaurs, while Zanno and colleagues found them to be the most basal clade within Maniraptora in 2009, bracketed by Ornithomimosauria and Alvarezsauridae . Despite the additional fossil material, the interrelations within
15488-408: Was gone by the late Triassic. Digit I is reduced and generally do not touch the ground, and greatly reduced in some lineages. They also lack a digit V on their hands and have developed a furcula which is otherwise known as a wishbone. Early neotheropods like the coelophysoids have a noticeable kink in the upper jaw known as a subnarial gap. Averostrans are some of the most derived theropods and contain
15616-451: Was later realized that Therizinosaurus was an advanced therizinosaur more related to Alxasaurus than other dinosaur lineages, Therizinosauroidea was coined to include Alxasaurus and Therizinosauridae, and has largely replaced the use of the older name Segnosauria in phylogenetic studies, mainly because of the association of the name Segnosauria with the discredited idea that these animals were relatives of prosauropods . Therizinosauroidea
15744-488: Was no justification for separating it into another family. In 1982, Perle reported hindlimb fragments similar to those of Segnosaurus , and assigned them to Therizinosaurus , whose forelimbs had been found in almost the same location. He concluded that Therizinosauridae, Deinocheiridae, and Segnosauridae, which all had enlarged forelimbs, represented the same taxonomic group. Segnosaurus and Therizinosaurus were particularly similar, leading Perle to suggest they belonged in
15872-408: Was not associated with the holotype due to its large size (larger than the pelvis itself). Nevertheless, it seems to approach the size of the closer Segnosaurus . Some paleontologists proposed that Enigmosaurus was likely the same animal as Erlikosaurus , since both were found in the same geologic formation , Enigmosaurus is known from pelvic remains, whereas the pelvis of Erlikosaurus
16000-484: Was originally identified as a turtle when described from forelimb elements in 1954. Perle noted in 1979 that the Segnosaurus fossils were possibly representative of a new family of dinosaurs, which he tentatively classified as theropods (traditionally thought of as the "meat-eating" dinosaurs). He named the family Segnosauridae, with Segnosaurus as type genus and sole member. He distinguished Segnosauridae from
16128-403: Was possibly 3 meters longer than Tyrannosaurus , though Tyrannosaurus could still be more massive than Spinosaurus . Specimens such as Sue and Scotty are both estimated to be the heaviest theropods known to science. There is still no clear explanation for why these animals grew so heavy and bulky compared to the land predators that came before and after them. The largest extant theropod
16256-423: Was swimming near the surface of a river and just the tips of its toes and claws could touch the bottom. The tracks indicate a coordinated, left-right, left-right progression, which supports the proposition that theropods were well-coordinated swimmers. During the late Triassic , a number of primitive proto-theropod and theropod dinosaurs existed and evolved alongside each other. The earliest and most primitive of
16384-427: Was unknown, Barsbold considered it unlikely the Enigmosaurus pelvis belonged to it, since Erlikosaurus and Segnosaurus were so similar in other respects, while the pelvis of Enigmosaurus was very different from that of Segnosaurus . Barsbold found that segnosaurids were so peculiar compared to more typical theropods that they were either a very significant deviation in theropod evolution, or that they went "beyond
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