| Xixianykus Temporal range: Late Cretaceous, | |
|---|---|
Scientific classification  | |
| Domain: | Eukaryota |
| Kingdom: | Animalia |
| Phylum: | Chordata |
| Clade: | Dinosauria |
| Clade: | Saurischia |
| Clade: | Theropoda |
| Family: | † Alvarezsauridae |
| Genus: | † Xixianykus Xu et al, 2010 |
| Species: | †X. zhangi |
| Binomial name | |
| †Xixianykus zhangi Xu et al., 2010 | |
Xixianykus is a genus of alvarezsaurid theropod dinosaur from the late Cretaceous period of China. [1]
The fossil, holotype XMDFEC V0011, was found in the Majiacun Formation in Henan Province, China. The fossil consists of a partial skeleton, without the skull. Parts of the hind legs, pelvis and spine has also been recovered. Xixianykus is among the oldest of the derived alvarezsauroids, the parvicursorines, dated to the Santonian–Coniacian, as opposed to other parvicursorines, which are either Campanian or Maastrichtian. [2]
The type species is Xixianykus zhangi described in 2010 by Xu Xing. The genus name refers to Xixia County and to the Greek word for claw ("onyx"). The latter is a common element used in names for Alvarezsaurids. The species name is in honor of Zhang Xinglao.
Xixianykus was a small animal, about 50 centimetres (20 in) long and 20 centimetres (7.9 in) high. It is one of the smallest-known dinosaurs (not counting avians). It appears to have many adaptations towards a cursorial (running) lifestyle. It was about 50 centimetres long but had 20-centimetre-long (7.9 in) legs and a short femur combined with a long tibia and metatarsus, which are good indicators of it being a fast runner. [2] It was probably covered in feathers.
Microraptor is a genus of small, four-winged dromaeosaurid dinosaurs. Numerous well-preserved fossil specimens have been recovered from Liaoning, China. They date from the early Cretaceous Jiufotang Formation, 125 to 120 million years ago. Three species have been named, though further study has suggested that all of them represent variation in a single species, which is properly called M. zhaoianus. Cryptovolans, initially described as another four-winged dinosaur, is usually considered to be a synonym of Microraptor.
Alvarezsauridae is a family of small, long-legged dinosaurs. Although originally thought to represent the earliest known flightless birds, they are now thought to be an early diverging branch of maniraptoran theropods. Alvarezsaurids were highly specialized. They had tiny but stout forelimbs, with compact, bird-like hands. Their skeletons suggest that they had massive breast and arm muscles, possibly adapted for digging or tearing. They had long, tube-shaped snouts filled with tiny teeth. They have been interpreted as myrmecophagous, adapted to prey on colonial insects such as termites, with the short arms acting as effective digging instruments to break into nests.
Mei is a genus of duck-sized troodontid dinosaur first unearthed by paleontologists from the Yixian Formation in Liaoning, China in 2004. Mei lived during the Early Cretaceous period. The binomial name of its only species, Mei long, means sleeping dragon.
Alvarezsaurus is a genus of alvarezsaurid dinosaur from the Late Cretaceous, living in Argentina approximately 86 - 83 million years ago. It was a small dinosaur, measuring 1–1.4 m (3.3–4.6 ft) long and weighing approximately 3 kg (6.6 lb). It was found in the Bajo de la Carpa Formation and was named by paleontologist José Bonaparte in 1991 after the historian Don Gregorio Alvarez. The type species is A. calvoi.
Mononykus is a genus of alvarezsaurid dinosaur that lived during the Late Cretaceous in what is now Asia on the Nemegt Formation, about 70 million years ago.
Graciliraptor is a genus of theropod dinosaur from the early Cretaceous Period. It is a microraptorine dromaeosaurid.
Luanchuanraptor is a genus of dromaeosaurid theropod dinosaurs from the Late Cretaceous of China. The genus is based on a partial skeleton from the Qiupa Formation in Luanchuan, Henan. They were medium-sized dromaeosaurids, the first Asian dromaeosaurid taxa described from outside the Gobi Desert or northeastern China.
Ceratonykus is a monospecific genus of alvarezsaurid dinosaur from Mongolia that lived during the Late Cretaceous in what is now the Barun Goyot Formation. The type and only species, Ceratonykus oculatus, is known from a fragmentary skeleton, including an incomplete skull, of an adult individual. It was named and described in 2009 by Vladimir Alifanov and Rinchen Barsbold. Its describers questioned the traditional placement of alvarezsaurs in Theropoda, instead suggesting they were ornithischians, but this has not been accepted since. Ceratonykus has an estimated length of 75 centimetres and weight of 760 grams. It has been considered as a possible junior synonym of Parvicursor.
Alvarezsauroidea is a group of small maniraptoran dinosaurs. Alvarezsauroidea, Alvarezsauridae, and Alvarezsauria are named for the historian Gregorio Álvarez, not the more familiar physicist Luis Alvarez, or his son geologist Walter Alvarez who jointly proposed that the Cretaceous–Paleogene extinction event was caused by an impact event. The group was first formally proposed by Choiniere and colleagues in 2010, to contain the family Alvarezsauridae and non-alvarezsaurid alvarezsauroids, such as Haplocheirus, which is the basalmost of the Alvarezsauroidea. The discovery of Haplocheirus extended the stratigraphic evidence for the group Alvarezsauroidea about 63 million years further in the past. The division of Alvarezsauroidea into the Alvarezsauridae and the non-alvarezsaurid alvarezsauroids is based on differences in their morphology, especially in their hand morphology.
The Majiacun Formation is a Santonian to Coniacian geologic formation in China. Dinosaur remains are among the fossils that have been recovered from the formation.
Linhenykus is an extinct genus of alvarezsaurid theropod dinosaur from the Late Cretaceous of Inner Mongolia, China. It is the most basal known member of the Parvicursorinae. The genus gets its name from Linhe, a city near the site where the fossil was first found and Greek nykus, "claw". The specific name is derived from Greek monos, "single", and daktylos, "finger", a reference to the fact that it is the only known non-avian dinosaur to have had but a single digit.
Yutyrannus is a genus of proceratosaurid tyrannosauroid dinosaur which contains a single known species, Yutyrannus huali. This species lived during the early Cretaceous period in what is now northeastern China. Three fossils of Yutyrannus huali —all found in the rock beds of Liaoning Province— are currently the largest-known carnivorous dinosaur specimens that preserve direct evidence of feathers.
Aorun is a genus of carnivorous theropod dinosaur first discovered in 2006, with its scientific description published in 2013. It is one of the oldest known coelurosaurian dinosaurs and is estimated to have lived ~161.6 million years ago during the Late Jurassic Period. It is the fifth extinct theropod discovered from Wucaiwan, China.
Wulatelong is an extinct genus of basal oviraptorid dinosaur known from the Late Cretaceous Wulansuhai Formation of Bayan Mandahu, Linhe District of Inner Mongolia, northern China. It contains a single species, Wulatelong gobiensis.
Zhuchengtitan is a genus of titanosaurian sauropod dinosaur from the Late Cretaceous of Shandong, China. It contains a single species, Z. zangjiazhuangensis, named by Mo Jinyou and colleagues in 2017 from a single humerus. Zhuchengtitan can be identified by the extreme width of the top end of its humerus, as well as the expansion of the deltopectoral crest on its humerus; both of these characteristics indicate that it was likely closely related to Opisthocoelicaudia. However, it differs from the latter by the flatter bottom articulating surface of its humerus. Zhuchengtitan lived in a floodplain environment alongside Shantungosaurus, Zhuchengtyrannus, and Sinoceratops.
Qiupanykus is a genus of alvarezsaurid coelurosaur theropod from the Late Cretaceous Qiupa Formation of southern China.
Ondogurvel is a genus of alvarezsaurid dinosaur from the Late Cretaceous (Campanian) Barun Goyot Formation in southern Mongolia. The type and only species is O. alifanovi, known from a partial skeleton consisting of fragments of two last dorsal vertebrae, three anterior sacral vertebrae, right ilium, left and right pubis and ischium, articulated right tibia, fibula, metatarsals II and IV, and phalanges IV-1 and IV-2, right carpometacarpus, left and right manual phalanx II-1, right femur, left pedal phalanx II-1, and fragments of unidentified phalanges.
Dzharaonyx is a genus of alvarezsaurid theropod dinosaur from the Late Cretaceous Bissekty Formation of Uzbekistan. The type species is Dzharaonyx eski; eski being an Uzbek word for "old".
Ruixinia is an extinct genus of somphospondylan titanosauriform dinosaur from the Early Cretaceous (Barremian) Yixian Formation of China. The genus contains a single species, Ruixinia zhangi. The Ruixinia holotype is a partial articulated skeleton with the most complete series of caudal vertebrae known from any Asian titanosauriform.
Jaculinykus is an extinct genus of alvarezsaurid theropod dinosaur from the Late Cretaceous Baruungoyot Formation of Mongolia. The genus contains a single species, J. yaruui, known from a nearly complete articulated skeleton including bones of the skull. Jaculinykus is notable for its unique hand, which has a hypertrophied first digit and greatly reduced second digit, which is intermediate between the tridactyl hand of Shuvuuia and monodactyl hand of Linhenykus.
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