Sinovenator Temporal range: Early Cretaceous, | |
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Fossil specimen, Tianjin Natural History Museum | |
Scientific classification ![]() | |
Domain: | Eukaryota |
Kingdom: | Animalia |
Phylum: | Chordata |
Clade: | Dinosauria |
Clade: | Saurischia |
Clade: | Theropoda |
Family: | † Troodontidae |
Subfamily: | † Sinovenatorinae |
Genus: | † Sinovenator Xu et al., 2002 |
Species: | †S. changii |
Binomial name | |
†Sinovenator changii Xu et al., 2002 | |
Sinovenator (meaning "Chinese hunter") is a genus of troodontid dinosaur from China. It is from the early Cretaceous Period.
Two specimens of a troodontid were described in 2002. They are both housed in the Institute of Vertebrate Paleontology and Paleoanthropology, under the specimen numbers IVPP V 12615 and IVPP V 12583. Xu Xing, Mark Norell, and colleagues authored the study describing them, finding the specimens to represent a new taxon, for which was chosen the binomial Sinovenator changii. The generic name was derived from the Latin word Sinae, for China, and Venator, or "hunter". Meemann Chang is honoured by the species name for her contributions to the study of the Jehol Fauna. [1] As Chang is a female researcher, the epithet should have been "changae"; however, such mistakes cannot be emended according to the rules of the ICZN and therefore forms such as "Sinovenator changae" or "Sinovenator changiae" that sometimes appear in the literature, are incorrect.[ citation needed ]
The type specimen or holotype of Sinovenator changii is IVPP 12615, a partial skull and disarticulated skeleton. An additional specimen was by the original publication scientifically described and assigned as the paratype of the species: an incomplete but articulated postcranial skeleton, numbered IVPP 12583. [1] A third specimen was referred: IVPP V14322, a fragmentary skeleton. All three are in the collection of the IVPP in Beijing, China. However, Sinovenator fossils appear to be common in the Lujiatun Beds. In a 2006 survey of the Jehol Biota, Xu and Norell reported that hundreds of undescribed specimens are known. [2] The fossils have been preserved three-dimensionally, not strongly compressed on a slab.
In 2014, the wrist of one specimen was described, IVPP V14009, an adult. [3] In 2018, PMOL-AD00102, consisting of a partial skull and mandibles, and six cervical vertebrae, was referred to the taxon. [4]
Sinovenator is a troodontid, a group of small, bird-like, gracile maniraptorans. All troodontids have many unique features of the skull, such as closely spaced teeth in the lower jaw, and large numbers of teeth. Troodontids have sickle-claws and raptorial hands, and some of the highest non-avian encephalization quotients, meaning they were behaviourally advanced and had keen senses. [5] The holotype individual of Sinovenator was about the size of a chicken, less than a metre long. [6] In 2010, Gregory S. Paul estimated the weight of a one metre long individual at 2.5 kilogrammes. [7] However, the holotype and paratype are subadults; specimens are known with about twice their length. This makes it one of the larger species of troodontids in the ecosystem of the Yixian Formation, the formation where it was found.
In the original description some distinguishing traits or autapomorphies were established. The front edge of the antorbital fenestra, the large skull opening in front of the eye socket, is straight and vertically oriented. The frontal bone shows a vertical ridge touching the lacrimal bone. The surangular in the lower jaw has a T-shaped cross-section. The shinbone has a vertical ridge on the upper outer side, the crista cnemialis, touching a lower vertical ridge, the crista fibularis. [6]
There is a number of other notable traits. The upper branch of the praemaxilla excludes the maxilla from the nostril. The premaxillary teeth lack denticles; those on the maxillary teeth are small. The maxillary tooth row is positioned at some distance from the jaw rim. A fenestra promaxillaris is present. The branch of the jugal towards the postorbital is long, slender and inclined to the rear. The foramen magnum is much larger than the occipital condyle. The braincase lacks a recessus suboticus and a crista otosphenoidalis. The rear of the pterygoid has a secondary, rod-like, process. The front dentary teeth are closely packed. The rear of the surangular is extraordinarily deep. [6]
Five sacrals are present, those of the middle being clearly larger. The ilium is relatively small. The ischium is bird-like: small with a low obturator process and processes on the upper and lower rear edge. The shinbone is wide at the top and has a roughly rectangular lower joint surface. The fourth metatarsal is not strongly developed but the second metatarsal is small. The third metatarsal is pinched at the top but still visible at the upper front of the metatarsus, conforming to the subarctometatarsal condition. [6]
In 2002 Sinovenator was placed in the Troodontidae. [1]
Sinovenator is a basal or "primitive" troodontid, and shares features with the most basal dromaeosaurids and Avialae. It thus was one of the first fossil specimens conclusively demonstrating the close relation of these three groups in the overarching Paraves. A typical basal trait is the orientation of the pubic bone to the rear, similar to the situation in the Dromaeosauridae and basal birds. This proves that the orientation to the front with later troodontids, is a reversal and not a trait directly inherited from older theropods that also possess a forward pointing pubic bone. Another basal character is the lack of a bulla, a swollen region on the underside of the braincase. This indicates that the similar bulla with the Ornithomimosauria presents a case of parallel evolution and is not a proof for a Bullatosauria, an earlier presumed close relationship between troodontids and ornithomimosaurs.[ citation needed ]
Originally, the basal position of Sinovenator seemed to be corroborated by a very high age, the fossils being assumed to date from the Hauterivian. Later research however, indicated that the layers were younger.[ citation needed ]
In 2017, a study by Shen et al., describing the genus Daliansaurus found Sinovenator to form a monophyletic group with other troodontids from the Yixian Formation, named Sinovenatorinae. A wide, flattened fourth metatarsal was found to be a synapomorphy uniting this group. The study recovered the following cladogram: [8]
Deinonychosauria |
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A 2018 study by Yin et al. instead found the Chinese troodontids to form an intermediate grade: [4]
Paraves |
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Troodontidae is a clade of bird-like theropod dinosaurs. During most of the 20th century, troodontid fossils were few and incomplete and they have therefore been allied, at various times, with many dinosaurian lineages. More recent fossil discoveries of complete and articulated specimens, have helped to increase understanding about this group. Anatomical studies, particularly studies of the most primitive troodontids, like Sinovenator, demonstrate striking anatomical similarities with Archaeopteryx and primitive dromaeosaurids, and demonstrate that they are relatives comprising a clade called Paraves.
Beipiaosaurus is a genus of therizinosauroid theropod dinosaurs that lived in Asia 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.
Sinornithosaurus is a genus of feathered dromaeosaurid dinosaur from the early Cretaceous Period of the Yixian Formation in what is now China. It was the fifth non–avian feathered dinosaur genus discovered by 1999. The original specimen was collected from the Sihetun locality of western Liaoning. It was found in the Jianshangou beds of the Yixian Formation, dated to 124.5 million years ago. Additional specimens have been found in the younger Dawangzhangzi bed, dating to around 122 million years ago.
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.
Liaoceratops, meaning "Liaoning horned face", is a ceratopsian dinosaur believed to be an early relative of the horned ceratopsids. It lived in the Early Cretaceous, 126 million years ago. It was discovered in China by a team of American and Chinese scientists. Liaoceratops was much smaller than its later relatives, but offers a glimpse into the early evolution of this group of dinosaurs.
Byronosaurus is a genus of troodontid dinosaur from the Late Cretaceous Period of Mongolia.
Sinornithoides is a genus of troodontid theropod dinosaurs containing the single species Sinornithoides youngi. S. youngi lived during the Early Cretaceous. It measured approximately one meter long (3.3 ft). It lived in Inner Mongolia, China, and probably ate invertebrates and other small prey. They lived in what is now Mongolia, which was part of Laurasia.
Sinusonasus is a genus of dinosaurs from the Early Cretaceous Period, recovered from the Yixian Formation. It lived in what is now the Liaoning Province of China. Sinusonasus was a theropod, specifically a troodontid dinosaur.
Liaoningosaurus is an unusual genus of basal ankylosaurid dinosaur from the Liaoning Province, China that lived during the Early Cretaceous in what is now the Yixian and Jiufotang Formation. The type and only species, Liaoningosaurus paradoxus, is known from more than 20 specimens, with some representing juveniles. It was named in 2001 by Xu, Wang and You.
Jeholosaurus is a genus of neornithischian dinosaur from the Early Cretaceous Period. It is thought to have been a herbivorous small ornithopod.
Graciliraptor is a genus of theropod dinosaur from the early Cretaceous Period. It is a microraptorine dromaeosaurid.
Dongbeititan is a genus of sauropod dinosaur from the Early Cretaceous-age Yixian Formation of Beipiao, Liaoning, China. It is based on holotype DNHM D2867, a partial postcranial skeleton including bones from the limbs, shoulder and pelvic girdles, and vertebrae, which was described in 2007. Its describers suggested it was as a basal titanosauriform, not as derived as Gobititan or Jiutaisaurus, but more derived than Euhelopus, Fusuisaurus, and Huanghetitan. The type species is D. dongi, and it is the first named sauropod from the Yixian Formation, which is part of the well-known Jehol Group. The genus name refers to the region Dongbei and to Greek titan, "giant". The specific name honours the Chinese paleontologist Dong Zhiming. Like other sauropods, Dongbeititan would have been a large quadrupedal herbivore.
Linhevenator is a genus of short-armed troodontid theropod dinosaur from the Late Cretaceous (Campanian) Bayan Mandahu Formation of Bayan Mandahu, Inner Mongolia, China.
Philovenator is an extinct genus of troodontid paravian dinosaurs from the Wulansuhai Formation of Inner Mongolia, China. Its specific name honors Phillip J. Currie.
Jinfengopteryginae is a subfamily of bird-like theropod dinosaurs known from the Cretaceous of Eurasia. This group includes relatively few genera, with members discovered in 2005 but the name erected in 2012. Like other troodontids, this group of dinosaurs resided in the Paraves potentially close to the Avialae.
Gobivenator is an extinct genus of troodontid theropod dinosaur known from the late Campanian Djadokhta Formation of central Gobi Desert, Mongolia. It contains a single species, Gobivenator mongoliensis. G. mongoliensis is known from a single individual, which represents the most complete specimen of a Late Cretaceous troodontid currently known.
This timeline of troodontid research is a chronological listing of events in the history of paleontology focused on the troodontids, a group of bird-like theropod dinosaurs including animals like Troodon. Troodontid remains were among the first dinosaur fossils to be reported from North America after paleontologists began performing research on the continent, specifically the genus Troodon itself. Since the type specimen of this genus was only a tooth and Troodon teeth are unusually similar to those of the unrelated thick-headed pachycephalosaurs, Troodon and its relatives would be embroiled in taxonomic confusion for over a century. Troodon was finally recognized as distinct from the pachycephalosaurs by Phil Currie in 1987. By that time many other species now recognized as troodontid had been discovered but had been classified in the family Saurornithoididae. Since these families were the same but the Troodontidae named first, it carries scientific legitimacy.
Jianianhualong is a genus of troodontid theropod dinosaur from the Early Cretaceous of China. It contains a single species, Jianianhualong tengi, named in 2017 by Xu Xing and colleagues based on an articulated skeleton preserving feathers. The feathers at the middle of the tail of Jianianhualong are asymmetric, being the first record of asymmetrical feathers among the troodontids. Despite aerodynamic differences from the flight feathers of modern birds, the feathers in the tail vane of Jianianhualong could have functioned in drag reduction whilst the animal was moving. The discovery of Jianianhualong supports the notion that asymmetrical feathers appeared early in the evolutionary history of the Paraves.
Daliansaurus is a genus of small troodontid theropod dinosaur, measuring approximately 1 metre long, from the Early Cretaceous of China. It contains a single species, D. liaoningensis, named in 2017 by Shen and colleagues from a nearly complete skeleton preserved in three dimensions. Daliansaurus is unusual in possessing an enlarged claw on the fourth digit of the foot, in addition to the "sickle claw" found on the second digit of the feet of most paravians. It also has long metatarsal bones, and apparently possesses bird-like uncinate processes. In the Lujiatun Beds of the Yixian Formation, a volcanically-influenced region with a cold climate, Daliansaurus lived alongside its closest relatives - Sinovenator, Sinusonasus, and Mei, with which it forms the group Sinovenatorinae.
Liaoningvenator is a genus of troodontid theropod dinosaur from the Early Cretaceous of China. It contains a single species, L. curriei, named after paleontologist Phillip J. Currie in 2017 by Shen Cai-Zhi and colleagues from an articulated, nearly complete skeleton, one of the most complete troodontid specimens known. Shen and colleagues found indicative traits that placed Liaoningvenator within the Troodontidae. These traits included its numerous, small, and closely packed teeth, as well as the vertebrae towards the end of its tail having shallow grooves in place of neural spines on their top surfaces.
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