''Erketu'' (meaning "Erketü Tengri") is a genus of

somphospondylan Somphospondyli is an extinct clade of titanosauriform sauropods that lived from the Late Jurassic until the end of the Late Cretaceous, comprising all titanosauriforms more closely related to Titanosauria proper than Brachiosauridae. The remain ...

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

that lived in

Asia Asia ( , ) is the largest continent in the world by both land area and population. It covers an area of more than 44 million square kilometres, about 30% of Earth's total land area and 8% of Earth's total surface area. The continent, which ...

during the

Late Cretaceous The Late Cretaceous (100.5–66 Ma) is the more recent 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 ''cre ...

roughly between 96 million and 89 million years ago. It is known from the

Bayan Shireh Formation The Bayanshiree Formation (also known as Baynshiree/Baynshire, Baynshirenskaya Svita, Baysheen Shireh, or Bayan Shireh) is a geological formation in Mongolia, that dates to the Cretaceous period. It was first described and established by Vasilie ...

Mongolia Mongolia is a landlocked country in East Asia, bordered by Russia to the north and China to the south and southeast. It covers an area of , with a population of 3.5 million, making it the world's List of countries and dependencies by po ...

and its fossils were between 2002 and 2003 during field expeditions. ''Erketu'' was first described in 2006 and later on in 2010 due to some cervicals that were left behind in the expedition. ''Erketu'' represents one of the first sauropods described from the Bayan Shireh Formation. The elongated cervical vertebrae of ''Erketu'' indicates that it was the sauropod with the longest neck relative to its body size.

Discovery and naming

The first remains of ''Erketu'' were found back in 2002 by the American Museum of Natural History–Mongolian Academy of Sciences expedition conducted in

. The team discovered the outcrops of the new locality Bor Guvé, which overlies the Khara Kuthul locality and therefore is referable to the

. The unearthed specimen, IGM 100/1803, was found in exposure at the sediments of Bor Guvé, mainly composed by

sandstone Sandstone is a Clastic rock#Sedimentary clastic rocks, clastic sedimentary rock composed mainly of grain size, sand-sized (0.0625 to 2 mm) silicate mineral, silicate grains, Cementation (geology), cemented together by another mineral. Sand ...

and

interbedded In geology, interbedding occurs when beds (layers of rock) of a particular lithology lie between or alternate with beds of a different lithology. For example, sedimentary rocks may be interbedded if there were sea level variations in their sedimen ...

grey

siltstones Siltstone, also known as aleurolite, is a clastic sedimentary rock that is composed mostly of silt Silt is granular material of a size between sand and clay and composed mostly of broken grains of quartz. Silt may occur as a soil (often mixed ...

, suggesting a

fluvial A river is a natural stream of fresh water that flows on land or inside caves towards another body of water at a lower elevation, such as an ocean, lake, or another river. A river may run dry before reaching the end of its course if it ru ...

environment that is consistent with the Bayan Shireh Formation. Collected elements are mainly represented by

cervical vertebrae In tetrapods, cervical vertebrae (: vertebra) are the vertebrae of the neck, immediately below the skull. Truncal vertebrae (divided into thoracic and lumbar vertebrae in mammals) lie caudal (toward the tail) of cervical vertebrae. In saurop ...

and postcranial remains, such as the partial right

sternum The sternum (: sternums or sterna) or breastbone is a long flat bone located in the central part of the chest. It connects to the ribs via cartilage and forms the front of the rib cage, thus helping to protect the heart, lungs, and major bl ...

tibia The tibia (; : tibiae or tibias), also known as the shinbone or shankbone, is the larger, stronger, and anterior (frontal) of the two Leg bones, bones in the leg below the knee in vertebrates (the other being the fibula, behind and to the outsi ...

and

fibula The fibula (: fibulae or fibulas) or calf bone is a leg bone on the lateral side of the tibia, to which it is connected above and below. It is the smaller of the two bones and, in proportion to its length, the most slender of all the long bones. ...

with

astragalus Astragalus may refer to: * ''Astragalus'' (plant), a large genus of herbs and small shrubs *Astragalus (bone) The talus (; Latin for ankle or ankle bone; : tali), talus bone, astragalus (), or ankle bone is one of the group of foot bones known ...

and

calcaneum In humans and many other primates, the calcaneus (; from the Latin ''calcaneus'' or ''calcaneum'', meaning heel; : calcanei or calcanea) or heel bone is a bone of the tarsus of the foot which constitutes the heel. In some other animals, it is t ...

. The remains became the

holotype A holotype (Latin: ''holotypus'') is a single physical example (or illustration) of an organism used when the species (or lower-ranked taxon) was formally described. It is either the single such physical example (or illustration) or one of s ...

for the new genus and species ''Erketu ellisoni'', first described in

2006 2006 was designated as the International Year of Deserts and Desertification. Events January * January 1– 4 – Russia temporarily cuts shipment of natural gas to Ukraine during a price dispute. * January 12 – A stampede during t ...

by Daniel Ksepka and

Mark Norell Mark Allen Norell (born July 26, 1957) is an American vertebrate paleontologist. He is currently the chairman of paleontology and a research associate at the American Museum of Natural History. He is best known as the discoverer of the first ...

of the

American Museum of Natural History The American Museum of Natural History (AMNH) is a natural history museum on the Upper West Side of Manhattan in New York City. Located in Theodore Roosevelt Park, across the street from Central Park, the museum complex comprises 21 interconn ...

. The generic name of this particular sauropod species is named after the creator god (tengri) of the Mongolian

shamanism Shamanism is a spiritual practice that involves a practitioner (shaman) interacting with the spirit world through altered states of consciousness, such as trance. The goal of this is usually to direct spirits or spiritual energies into ...

, Erketü. The specific name, ''ellisoni'', is in honor to the American Museum of Natural History's senior principal

paleoartist Paleoart (also spelled palaeoart, paleo-art, or paleo art) is any original artistic work that attempts to depict prehistoric life according to scientific evidence.#Anson, Ansón, Fernández & Ramos (2015) pp. 28–34. Works of paleoart may be r ...

, and close friend of Norell: Mick Ellison. In 2003 the team returned to the site and recovered three additional cervicals that were left behind during the first field expedition, and consequently described in

2010 The year saw a multitude of natural and environmental disasters such as the 2010 Haiti earthquake, the Deepwater Horizon oil spill, and the 2010 Chile earthquake. The 2009 swine flu pandemic, swine flu pandemic which began the previous year ...

Description

''Erketu'' was a relatively large sauropod, with an estimated length of and a weight of . Its neck was estimated to be twice as long as its body, which may be a record for neck to body ratio. The exact ratio is unknown, because no

dorsal vertebrae In vertebrates, thoracic vertebrae compose the middle segment of the vertebral column, between the cervical vertebrae and the lumbar vertebrae. In humans, there are twelve thoracic vertebra (anatomy), vertebrae of intermediate size between the ce ...

of ''E. ellisoni'' have been reported, although some hindlimb material suggests the approximate size of the body. The long neck of ''Erketu'' is the result of the individual vertebrae being greatly elongated; it is unknown if the number of cervical vertebrae was increased. ''Erketu'' is also diagnosed by bifurcate anterior cervical neural spines, another unusual trait for a titanosauriform. The preserved cervicals include the

atlas An atlas is a collection of maps; it is typically a bundle of world map, maps of Earth or of a continent or region of Earth. Advances in astronomy have also resulted in atlases of the celestial sphere or of other planets. Atlases have traditio ...

axis An axis (: axes) may refer to: Mathematics *A specific line (often a directed line) that plays an important role in some contexts. In particular: ** Coordinate axis of a coordinate system *** ''x''-axis, ''y''-axis, ''z''-axis, common names ...

and C3 to C9, however, the sixth is missing, giving a total of eight preserved cervical vertebrae. Erketu Scale

The preserved sternum is rather thickened at some borders and shows a very deep lateral edge, it measures about long. The right hindlimb elements were nicely found in articulation and they resemble those of ''

Gobititan ''Gobititan'' is a genus of herbivorous sauropod dinosaur from the Aptian faunal stage of the Early Cretaceous. The name of this genus is derived from the Gobi Desert region and the Titans of Greek mythology, which is a reference to its large bo ...

''. The tibia is very straight, measuring in total length, it has slightly expanded ends and in comparison to that of ''

Opisthocoelicaudia ''Opisthocoelicaudia'' is a genus of sauropod dinosaur of the Late Cretaceous Period discovered in the Gobi Desert of Mongolia. The type species is ''Opisthocoelicaudia skarzynskii''. A well-preserved skeleton lacking only the head and neck wa ...

'', the anterior and distal expansions are not very developed. The fibula is longer than the tibia with a length of , however, it appears to be broken on the distal end of one of the trochanters.

Classification

The phylogenetic analysis of sauropods performed by its describers indicates that ''Erketu'' is a basal somphospondylian (the

clade In biology, a clade (), also known as a Monophyly, monophyletic group or natural group, is a group of organisms that is composed of a common ancestor and all of its descendants. Clades are the fundamental unit of cladistics, a modern approach t ...

of all

macronarians Macronaria is a clade of sauropod dinosaurs. Macronarians are named after the large diameter of the nasal opening of their skull, known as the external naris, which exceeded the size of the orbit, the skull opening where the eye is located (hence ...

closer to

titanosaurs Titanosaurs (or titanosaurians; members of the group Titanosauria) were a diverse group of Sauropoda, sauropod dinosaurs, including genera from all seven continents. The titanosaurs were the last surviving group of long-necked sauropods, with tax ...

than to

brachiosaurids The Brachiosauridae ("arm lizards", from Greek ''brachion'' (βραχίων) = "arm" and ''sauros'' = "lizard") are a family or clade of herbivorous, quadrupedal sauropod dinosaurs. Brachiosaurids had long necks that enabled them to access the le ...

), and is most closely related to

Titanosauria Titanosaurs (or titanosaurians; members of the group Titanosauria) were a diverse group of Sauropoda, sauropod dinosaurs, including genera from all seven continents. The titanosaurs were the last surviving group of long-necked sauropods, with tax ...

, being a close relative of ''

Euhelopus ''Euhelopus'' is a genus of sauropod dinosaur that lived between 145 and 133 million years ago during the Berriasian and Valanginian ages of the Early Cretaceous in what is now Shandong Province in China. It was a large quadrupedal herbivore. Lik ...

''. During the description of ''

Europatitan ''Europatitan'' is an extinct genus of Somphospondyli, somphospondylan sauropod from the Early Cretaceous Castrillo de la Reina Formation of Iberia, known from a relatively complete specimen discovered in the early 2000s. It contains a single spe ...

'' in 2017, a new cladistic analysis was performed. Here, ''Erketu'' was recovered in a

polytomy An internal node of a phylogenetic tree is described as a polytomy or multifurcation if (i) it is in a rooted tree and is linked to three or more child subtrees or (ii) it is in an unrooted tree and is attached to four or more branches. A tree ...

along ''

Chubutisaurus ''Chubutisaurus'' (meaning "Chubut lizard") is a genus of somphospondylan sauropod dinosaur from the Early Cretaceous Cerro Barcino Formation (Albian) of Argentina. The type species, ''Chubutisaurus insignis'', was described by del Corro in 197 ...

'' within the Somphospondyli:

Paleoecology

The remains of ''Erketu'' are attributed to the

, which is believed to have been dominated by fluvial and lacustrine environments, such as large

meanders A meander is one of a series of regular sinuous curves in the channel of a river or other watercourse. It is produced as a watercourse erodes the sediments of an outer, concave bank ( cut bank or river cliff) and deposits sediments on an inn ...

and

lakes A lake is often a naturally occurring, relatively large and fixed body of water on or near the Earth's surface. It is localized in a basin or interconnected basins surrounded by dry land. Lakes lie completely on land and are separate from t ...

but also a notorious semi-arid climate. The age is estimated to be around 95.9 ± 6.0 million to 89.6 ± 4.0 million years ago,

Cenomanian The Cenomanian is, in the International Commission on Stratigraphy's (ICS) geological timescale, the oldest or earliest age (geology), age of the Late Cretaceous epoch (geology), Epoch or the lowest stage (stratigraphy), stage of the Upper Cretace ...

Coniacian The Coniacian is an age or stage in the geologic timescale. It is a subdivision of the Late Cretaceous Epoch or Upper Cretaceous Series and spans the time between 89.8 ± 1 Ma and 86.3 ± 0.7 Ma (million years ago). The Coniacian is preceded by ...

stages. Here, ''Erketu'' lived alongside diverse dinosaur fauna, such as the theropods ''

Achillobator ''Achillobator'' ( ; meaning "Achilles hero") is a genus of large dromaeosaurid theropod dinosaur that lived during the Late Cretaceous period about 96 million to 89 million years ago in what is now the Bayan Shireh Formation of Mongolia. The ge ...

'' and ''

Khankhuuluu ''Khankhuuluu'' ( ; ) is an extinct genus of early tyrannosauroid theropod dinosaurs from the Late Cretaceous of what is now the Gobi Desert in Mongolia. The genus contains a Monotypic taxon, single species, ''Khankhuuluu mongoliensis'', known fr ...

'', the abundant hadrosauroid ''

Gobihadros ''Gobihadros'' is a genus of basal hadrosauroid dinosaur that lived in Asia during the Late Cretaceous period in what is now the Bayan Shireh Formation (Cenomanian-Santonian). It contains only the type species ''Gobihadros mongoliensis''. It has ...

'', heavy armored ankylosaurs ''

Talarurus ''Talarurus'' ( ; meaning "basket tail" or "wicker tail") is a genus of ankylosaurid dinosaur that lived in Asia during the Late Cretaceous period, about 96 million to 89 million years ago. The first remains of ''Talarurus'' were discovered in 1 ...

'' and ''

Tsagantegia ''Tsagantegia'' (; meaning Tsagan Teg) is a genus of medium-sized ankylosaurid thyreophoran dinosaur that lived in Asia during the Late Cretaceous period. The genus is monotypic, including only the type species, ''T. longicranialis''. The specime ...

'', and the well-known therizinosaurs ''

Erlikosaurus ''Erlikosaurus'' (meaning "Erlik's lizard") 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, da ...

'' and ''

Segnosaurus ''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 Go ...

''. The locality of ''Erketu'' has also yielded an indeterminate/unnamed titanosaur and very abundant fossilized

fruits In botany, a fruit is the seed-bearing structure in flowering plants (angiosperms) that is formed from the ovary after flowering. Fruits are the means by which angiosperms disseminate their seeds. Edible fruits in particular have long propaga ...

. Some ecological niches were filled by several dinosaurs, such as the

browsers Browse, browser, or browsing may refer to: Computing *Browser service, a feature of Microsoft Windows to browse shared network resources *Code browser, a program for navigating source code *File browser or file manager, a program used to manage f ...

''Erlikosaurus'', ''Segnosaurus'' and ''Tsagantegia''; in contrast, ''Talarurus'' was a grazer. ''Erketu'' in the other hand, due to its very long neck, was likely a high browser.

References

{{Taxonbar, from=Q138872 Macronaria Dinosaur genera Late Cretaceous dinosaurs Taxa named by Mark Norell Fossil taxa described in 2006 Dinosaurs of Mongolia

Discovery and naming

Description

Classification

Paleoecology

See also

References