Temporal range: Late Cretaceous, Santonian
|Life restoration of H. griva|
Makovicky et al., 2011
Makovicky et al., 2011
Haya is known from several well-preserved specimens which collected in the Khugenetslavkant locality by the joint Mongolian Academy of Sciences from 2002 to 2007, from the Javkhlant Formation. The locality probably dates to the Santonian stage of the Late Cretaceous. The holotype IGM 100/2017 is composed of a complete and well preserved skull with some postcranial elements associated to it. Referred materials include IGM 100/1324, isolated left femur, IGM 100/2013, postcranial elements, IGM 100/2014, a crushed skull and postcranial elements, IGM 100/2015, a nearly complete postcranial skeleton, IGM 100/2016, a partial juvenile skull, IGM 100/2018, an isolated mandible with some teeth, IGM 100/2019, a nearly complete skull and skeleton and IGM 100/2020, postcranial fragments. One skeleton of Haya, IGM 100/2015, preserves a large mass of gastroliths. A cladistic analysis found it to form a clade with Jeholosaurus and Changchunsaurus within Ornithopoda. Han et al. named this clade "Jeholosauridae" in 2012.
Haya was first named by Peter J. Makovicky, Brandon M. Kilbourne, Rudyard W. Sadleir and Mark A. Norell in 2011 and the type species is Haya griva. The generic name and the specific name are both derived from the Sanskrit for the "Haryagriva" avatar of the Hindu god Vishnu, depicted with a horse head. This name refers to the elongate horse-like skull of Haya and the appearance of this deity in the Buddhist art of Mongolia.
Size has been one of the most interesting aspects of dinosaur science to the general public and to scientists. Dinosaurs show some of the most extreme variations in size of any land animal group, ranging from the tiny hummingbirds, which can weigh as little as three grams, to the extinct titanosaurs, which could weigh as much as 90 tonnes (89 long tons; 99 short tons).Scientists will probably never be certain of the largest and smallest dinosaurs to have ever existed. This is because only a tiny fraction of animals ever fossilize, and most of these remain buried in the earth. Few of the specimens that are recovered are complete skeletons, and impressions of skin and other soft tissues are rare. Rebuilding a complete skeleton by comparing the size and morphology of bones to those of similar, better-known species is an inexact art, and reconstructing the muscles and other organs of the living animal is, at best, a process of educated guesswork. Weight estimates for dinosaurs are much more variable than length estimates, because estimating length for extinct animals is much more easily done from a skeleton than estimating weight. Estimating weight is most easily done with the laser scan skeleton technique that puts a "virtual" skin over it, but even this is only an estimate.Current evidence suggests that dinosaur average size varied through the Triassic, early Jurassic, late Jurassic and Cretaceous periods. Predatory theropod dinosaurs, which occupied most terrestrial carnivore niches during the Mesozoic, most often fall into the 100- to 1,000-kilogram (220 to 2,200 lb) category when sorted by estimated weight into categories based on order of magnitude, whereas recent predatory carnivoran mammals peak in the 10- to 100-kilogram (22 to 220 lb) category. The mode of Mesozoic dinosaur body masses is between one and ten metric tonnes. This contrasts sharply with the size of Cenozoic mammals, estimated by the National Museum of Natural History as about 2 to 5 kg (4.4 to 11.0 lb).Hayagriva
Hayagriva, also spelt Hayagreeva (IAST: hayagrīva, literally 'Horse-neck'), is a horse-headed avatar of the Lord Vishnu in Hinduism.Jvarasura
Jvarasura also called Jwarasura (Hindi: ज्वारासुर) in Hindu mythology is the fever-deity and consort of pox-deity goddess, Shitala.List of ornithopod type specimens
This list of ornithopod type specimens is a list of fossils serving as the official standard-bearers for inclusion in the species and genera of the dinosaur clade Ornithopoda, which includes the line of herbivorous dinosaurs culminating in the duck-billed hadrosaurs. Type specimens are definitionally members of biological taxa and additional specimens can only be "referred" to these taxa if an expert deems them sufficiently similar to the type.Neornithischia
Neornithischia ("new ornithischians") is a clade of the dinosaur order Ornithischia. They are the sister group of the Thyreophora within the clade Genasauria. Neornithischians are united by having a thicker layer of asymmetrical enamel on the inside of their lower teeth. The teeth wore unevenly with chewing and developed sharp ridges that allowed neornithischians to break down tougher plant food than other dinosaurs. Neornithischians include a variety of basal forms historically known as "hypsilophodonts", including the Parksosauridae; in addition, there are derived forms classified in the groups Marginocephalia and Ornithopoda. The former includes clades Pachycephalosauria and Ceratopsia, while the latter typically includes Hypsilophodon and the more derived Iguanodontia.