''Haya'' is an

extinct Extinction is the termination of a kind of organism or of a group of kinds (taxon), usually a species. The moment of extinction is generally considered to be the death of the last individual of the species, although the capacity to breed and ...

genus Genus ( plural genera ) is a taxonomic rank used in the biological classification of extant taxon, living and fossil organisms as well as Virus classification#ICTV classification, viruses. In the hierarchy of biological classification, genus com ...

of basal

neornithischian Neornithischia ("new ornithischians") is a clade of the dinosaur order Ornithischia. It is the sister group of the Thyreophora within the clade Genasauria. Neornithischians are united by having a thicker layer of asymmetrical enamel on the insi ...

dinosaur Dinosaurs are a diverse group of reptiles of the clade Dinosauria. They first appeared during the Triassic period, between 243 and 233.23 million years ago (mya), although the exact origin and timing of the evolution of dinosaurs is t ...

known from

Mongolia Mongolia; Mongolian script: , , ; lit. "Mongol Nation" or "State of Mongolia" () is a landlocked country in East Asia, bordered by Russia to the north and China to the south. It covers an area of , with a population of just 3.3 million, ...

Description

''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 Javkhlant Formation is a geological formation in Mongolia whose strata date back to the Late Cretaceous possibly Santonian to Campanian. Ceratopsian, ornithopod and theropod remains been found in the formation. A prominent fossilized therizino ...

and a few from the Zos Canyon locality of the

Gobi Desert The Gobi Desert (Chinese: 戈壁 (沙漠), Mongolian: Говь (ᠭᠣᠪᠢ)) () is a large desert or brushland region in East Asia, and is the sixth largest desert in the world. Geography The Gobi measures from southwest to northeast an ...

. Both localities probably date to the

Santonian The Santonian is an age in the geologic timescale or a chronostratigraphic stage. It is a subdivision of the Late Cretaceous Epoch or Upper Cretaceous Series. It spans the time between 86.3 ± 0.7 mya (million years ago) and 83.6 ± 0.7 mya. The ...

-Campanian stages of the

Late Cretaceous The Late Cretaceous (100.5–66 Ma) is the younger of two epochs into which the Cretaceous Period is divided in the geologic time scale. Rock strata from this epoch form the Upper Cretaceous Series. The Cretaceous is named after ''creta'', the ...

. The

holotype A holotype is a single physical example (or illustration) of an organism, known to have been used when the species (or lower-ranked taxon) was formally described. It is either the single such physical example (or illustration) or one of several ...

IGM Immunoglobulin M (IgM) is one of several isotypes of antibody (also known as immunoglobulin) that are produced by vertebrates. IgM is the largest antibody, and it is the first antibody to appear in the response to initial exposure to an antig ...

100/2017 is composed of a complete and well preserved

skull The skull is a bone protective cavity for the brain. The skull is composed of four types of bone i.e., cranial bones, facial bones, ear ossicles and hyoid bone. However two parts are more prominent: the cranium and the mandible. In humans, the ...

with some

postcrania Postcrania (postcranium, adjective: postcranial) in zoology and vertebrate paleontology is all or part of the skeleton apart from the skull. Frequently, fossil remains, e.g. of dinosaurs or other extinct tetrapods, consist of partial or isolated sk ...

l elements associated to it. Referred materials include IGM 100/1324, isolated left

femur The femur (; ), or thigh bone, is the proximal bone of the hindlimb in tetrapod vertebrates. The head of the femur articulates with the acetabulum in the pelvic bone forming the hip joint, while the distal part of the femur articulates with ...

, 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 In anatomy, the mandible, lower jaw or jawbone is the largest, strongest and lowest bone in the human facial skeleton. It forms the lower jaw and holds the lower tooth, teeth in place. The mandible sits beneath the maxilla. It is the only movabl ...

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

gastrolith A gastrolith, also called a stomach stone or gizzard stone, is a rock held inside a gastrointestinal tract. Gastroliths in some species are retained in the muscular gizzard and used to grind food in animals lacking suitable grinding teeth. In othe ...

Etymology

''Haya'' was first named by Peter J. Makovicky, Brandon M. Kilbourne, Rudyard W. Sadleir and Mark A. Norell in

2011 File:2011 Events Collage.png, From top left, clockwise: a protester partaking in Occupy Wall Street heralds the beginning of the Occupy movement; protests against Libyan dictator Muammar Gaddafi, who was killed that October; a young man celebrate ...

and the

type species In zoological nomenclature, a type species (''species typica'') is the species name with which the name of a genus or subgenus is considered to be permanently taxonomically associated, i.e., the species that contains the biological type specimen ...

is ''Haya griva''. The generic name and the

specific name Specific name may refer to: * in Database management systems, a system-assigned name that is unique within a particular database In taxonomy, either of these two meanings, each with its own set of rules: * Specific name (botany), the two-part (bino ...

are both derived from the

Sanskrit Sanskrit (; attributively , ; nominally , , ) is a classical language belonging to the Indo-Aryan branch of the Indo-European languages. It arose in South Asia after its predecessor languages had diffused there from the northwest in the late ...

for the "Hayagriva" avatar of the Hindu god

Vishnu Vishnu ( ; , ), also known as Narayana and Hari, is one of the principal deities of Hinduism. He is the supreme being within Vaishnavism, one of the major traditions within contemporary Hinduism. Vishnu is known as "The Preserver" within t ...

, 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.

Phylogeny

cladistic Cladistics (; ) is an approach to biological classification in which organisms are categorized in groups (" clades") based on hypotheses of most recent common ancestry. The evidence for hypothesized relationships is typically shared derived char ...

analysis found it to form a clade with '' Jeholosaurus'' and '' Changchunsaurus'' within Ornithopoda. Han ''et al.'' named this clade "

Jeholosauridae Jeholosaurids were herbivorous neornithischian dinosaurs from the Cretaceous Period (Aptian - Cenomanian). The family was first proposed by Han ''et al.'' in 2012. The jeholosaurids were defined as all neornithischians more closely related to ''J ...

" in 2012. The

cladogram A cladogram (from Greek ''clados'' "branch" and ''gramma'' "character") is a diagram used in cladistics to show relations among organisms. A cladogram is not, however, an evolutionary tree because it does not show how ancestors are related to d ...

below from a 2019 study by Herne ''et al.'' shows ''Haya's'' placement within Jeholosauridae, as well as relationships to similar neornithischians. In 2021, Daniel E. Barta and Mark A. Norell carried out a detailed analysis of the phylogenetic position of ''Haya'', recovering ''Haya'' outside of

, and instead as part of

Thescelosauridae Thescelosauridae is a clade of neornithischians from the Cretaceous of Asia, North America and possibly South America. The group was originally used as a name by Charles M. Sternberg in 1937, but was not formally defined until 2013, where it was ...

References

Late Cretaceous dinosaurs of Asia Fossil taxa described in 2011 Ornithischian genera {{Ornithischian-stub