The timeline of therizinosaur research is a chronological listing of events in the history of paleontology focused on therizinosaurs. They were unusually long-necked, pot-bellied, and large-clawed herbivorous theropods most 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.
Segnosaurus is a genus of therizinosaurid dinosaur that lived in what is now southeastern Mongolia during the Late Cretaceous, about 102–86 million years ago. Multiple incomplete but well-preserved specimens were discovered in the Gobi Desert in the 1970s, and in 1979 the genus and species Segnosaurus galbinensis were named. The generic name Segnosaurus means "slow lizard" and the specific name galbinensis refers to the Galbin region. The known material of this dinosaur includes the lower jaw, neck and tail vertebrae, the pelvis, shoulder girdle, and limb bones. Parts of the specimens have gone missing or become damaged since they were collected.
Therizinosaurus is a genus of very large therizinosaurid that lived in Asia during the Late Cretaceous period in what is now the Nemegt Formation around 72.1 million years ago to 66 million years ago. It contains a single species, Therizinosaurus cheloniformis. The first remains of Therizinosaurus were found in 1948 by a Mongolian field expedition at the Gobi Desert and later described by Evgeny Maleev in 1954. The genus is only known from a few bones, including gigantic manual unguals, from which it gets its name, and additional findings comprising fore and hindlimb elements that were discovered from the 1960s through the 1980s.
Maniraptora is a clade of coelurosaurian dinosaurs which includes the birds and the non-avian dinosaurs that were more closely related to them than to Ornithomimus velox. It contains the major subgroups Avialae, Dromaeosauridae, Troodontidae, Oviraptorosauria, and Therizinosauria. Ornitholestes and the Alvarezsauroidea are also often included. Together with the next closest sister group, the Ornithomimosauria, Maniraptora comprises the more inclusive clade Maniraptoriformes. Maniraptorans first appear in the fossil record during the Jurassic Period, and survive today as living birds.
Beipiaosaurus is a genus of therizinosauroid theropod dinosaurs that lived in China during the Early Cretaceous in the Yixian Formation. The first remains were found in 1996 and formally described in 1999. Before the discovery of Yutyrannus, Beipiaosaurus were among the heaviest dinosaurs known from direct evidence to be feathered. Beipiaosaurus is known from three reported specimens. Numerous impressions of feather structures were preserved that allowed researchers to determine the feathering color which turned out to be brownish.
Falcarius is a genus of primitive therizinosaur dinosaur that lived during the Early Cretaceous period in what is now North America. Its remains were first collected in the Cedar Mountain Formation in 1999, with subsequent findings made during the 2000s. The genus is known from multiple specimens ranging from immature to fully-grown individuals.
Therizinosaurs are an extinct group of large herbivorous theropod dinosaurs whose fossils have been found across the Middle Jurassic to Late Cretaceous deposits in Europe, Asia and North America. Various features of the forelimbs, skull and pelvis unite these finds as both theropods and maniraptorans, making them relatives of birds. The name of the representative genus, Therizinosaurus, is derived from the Greek θερίζω and σαῦρος. The older representative, Segnosaurus, is derived from the Latin sēgnis ('slow') and the Greek σαῦρος.
Nothronychus is a genus of therizinosaurid theropod dinosaurs that lived in North America during the Late Cretaceous period. The type species, Nothronychus mckinleyi, was described by James Kirkland and Douglas G. Wolfe in 2001. It was recovered near New Mexico's border with Arizona, in an area known as the Zuni Basin, from rocks assigned to the Moreno Hill Formation, dating to the Turonian stage of the Late Cretaceous. A second specimen, described in 2009 as a second species, Nothronychus graffami, was found in the Tropic Shale of Utah, dating between one million and a half million years older than N. mckinleyi.
Enigmosaurus is a genus of therizinosauroid that lived in Asia during 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.
Garudimimus is a genus of ornithomimosaur that lived in Asia during the Late Cretaceous. The genus is known from a single specimen found in 1981 by a Soviet-Mongolian paleontological expedition in the Bayan Shireh Formation and formally described in the same year by Rinchen Barsbold; the only species is Garudimimus brevipes. Several interpretations about the anatomical traits of Garudimimus were made in posterior examinations of the specimen, but most of them were criticized during its comprehensive redescription in 2005. Extensive undescribed ornithomimosaur remains at the type locality of Garudimimus may represent additional specimens of the genus.
Alxasaurus is a genus of therizinosauroid theropod dinosaurs from the Early Cretaceous Bayin-Gobi Formation of Inner Mongolia.
Therizinosauridae is an extinct family of derived (advanced) therizinosauroid dinosaurs whose fossil remains have been found in mostly Late Cretaceous boundary. Even though representative fossils have only been found throughout Asia and North America, the range of Therizinosauridae is believed to have spanned much of the supercontinent of Laurasia based on several footprints and isolated remains in Europe and Africa. Currently, Therizinosauridae comprises eight described and named taxa.
The Bayan Shireh Formation is a geological formation in Mongolia, that dates to the Cretaceous period. It was first described and established by Vasiliev et al. 1959.
Erlikosaurus is a genus of therizinosaurid that lived in Asia during the Late Cretaceous period. The fossils, a skull and some post-cranial fragments, were found in the Bayan Shireh Formation of Mongolia in 1972, dating to around 96 million and 89 million years ago. These remains were later described by Altangerel Perle and Rinchen Barsbold in 1980, naming the new genus and species Erlikosaurus andrewsi. It represents the second therizinosaur taxon from this formation with the most complete skull among members of this peculiar family of dinosaurs.
Eshanosaurus is a genus of a dinosaur from the early Jurassic Period. It is known only from a fossil partial lower jawbone, found in China. It may be a therizinosaurian, and if so the earliest known coelurosaur.
Neimongosaurus is a genus of herbivorous therizinosaur theropod dinosaur that lived in Asia during the Cenomanian stage of the Late Cretaceous period in what is now the Iren Dabasu Formation.
Nanshiungosaurus is a genus of therizinosaurid that lived in what is now Asia during the Late Cretaceous of South China. The type species, Nanshiungosaurus brevispinus, was first discovered in 1974 and described in 1979 by Dong Zhiming. It is represented by a single specimen preserving most of the cervical and dorsal vertebrae with the pelvis. A supposed and unlikely second species, "Nanshiungosaurus" bohlini, was found in 1992 and described in 1997. It is also represented by vertebrae but this species however, differs in geological age and lacks authentic characteristics compared to the type, making its affinity to the genus unsupported.
Suzhousaurus is a genus of large therizinosauroid dinosaur from the Early Cretaceous of China. The genus is known from two specimens discovered on the Xiagou Formation and Zhonggou Formation—which are situated in the Xinminbao Group. These findings were made during field-works in 1999 and 2004. Though Suzhousaurus is known from these two specimens, an earlier named and described therizinosauroid from the adjacent basin, "Nanshiungosaurus" bohlini, may be synonymous with the former. However, Suzhousaurus can not be compared to this species due to non-overlapping material and the loss of the same. Moreover, this synonymy will result in Suzhousaurus bohlini with "N". bohlini having priority.
Martharaptor is a genus of therizinosauroid theropod dinosaurs from the Early Cretaceous of the Cedar Mountain Formation in Utah. They can be distinguished from other therizinosauroids by means of several features of the skeleton which were intermediate between early therizinosaurs such as Falcarius and Beipiaosaurus, and more "advanced" members of the group like therizinosaurids. The deep and homogeneous hand claws clearly differ from the case in early therizinosauroids, but the foot has not yet acquired the robust morphology of therizinosaurids.
Lindsay E. Zanno is an American vertebrate paleontologist and a leading expert on theropod dinosaurs and Cretaceous paleoecosystems. She is the Head of Paleontology at the North Carolina Museum of Natural Sciences and an Associate Research Professor in the Department of Biological Sciences at North Carolina State University.
This timeline of oviraptorosaur research is a chronological listing of events in the history of paleontology focused on the oviraptorosaurs, a group of beaked, bird-like theropod dinosaurs. The early history of oviraptorosaur paleontology is characterized by taxonomic confusion due to the unusual characteristics of these dinosaurs. When initially described in 1924 Oviraptor itself was thought to be a member of the Ornithomimidae, popularly known as the "ostrich" dinosaurs, because both taxa share toothless beaks. Early caenagnathid oviraptorosaur discoveries like Caenagnathus itself were also incorrectly classified at the time, having been misidentified as birds.
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