Archaeornithomimus
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''Archaeornithomimus'' (meaning "ancient bird mimic") is a
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
ornithomimosaurian Ornithomimosauria ("bird-mimic lizards") are theropod dinosaurs which bore a superficial resemblance to the modern-day ostrich. They were fast, omnivorous or herbivorous dinosaurs from the Cretaceous Period of Laurasia (now Asia, Europe and North ...
theropod Theropoda (; ), whose members are known as theropods, is a dinosaur clade that is characterized by hollow bones and three toes and claws on each limb. Theropods are generally classed as a group of saurischian dinosaurs. They were ancestrally c ...
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 ...
that lived in
Asia Asia (, ) is one of the world's most notable geographical regions, which is either considered a continent in its own right or a subcontinent of Eurasia, which shares the continental landmass of Afro-Eurasia with Africa. Asia covers an area ...
during 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 ...
period, around 96 million years ago in the
Iren Dabasu Formation The Iren Dabasu Formation (also known as Erlian Formation) is a Late Cretaceous geologic formation in the Iren Nor region of Inner Mongolia. Dinosaur remains diagnostic to the genus level are among the fossils that have been recovered from the fo ...
.


Discovery and naming

In 1923, during the
American Museum of Natural History The American Museum of Natural History (abbreviated as AMNH) is a natural history museum on the Upper West Side of Manhattan in New York City. In Theodore Roosevelt Park, across the street from Central Park, the museum complex comprises 26 inter ...
expedition by
Roy Chapman Andrews Roy Chapman Andrews (January 26, 1884 – March 11, 1960) was an American explorer, adventurer and naturalist who became the director of the American Museum of Natural History. He led a series of expeditions through the politically disturbed C ...
to
Inner Mongolia Inner Mongolia, officially the Inner Mongolia Autonomous Region, is an autonomous region of the People's Republic of China. Its border includes most of the length of China's border with the country of Mongolia. Inner Mongolia also accounts for a ...
, Peter Kaisen discovered numerous theropod remains in three quarries. They consist of the largely disarticulated remains of several individuals and material of the skull and the lower jaws is lacking. These were named and shortly described by
Charles Whitney Gilmore Charles Whitney Gilmore (March 11, 1874 – September 27, 1945) was an American paleontologist who gained renown in the early 20th century for his work on vertebrate fossils during his career at the United States National Museum (now the N ...
in 1933 as a new species of ''
Ornithomimus ''Ornithomimus'' (; "bird mimic") is a genus of ornithomimid dinosaurs from the Late Cretaceous Period of what is now North America. ''Ornithomimus'' was a swift bipedal theropod which fossil evidence indicates was covered in feathers, equippe ...
'': ''Ornithomimus asiaticus''. The specific name refers to the Asian provenance. The species was placed in the new genus ''Archaeornithomimus'' by
Dale Russell Dale Alan Russell (27 December 1937 – 21 December 2019) was an American-Canadian geologist and palaeontologist. Throughout his career Russell worked as the Curator of Fossil Vertebrates at the Canadian Museum of Nature, Research Professor a ...
in 1972, making ''Archaeornithomimus asiaticus'' 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 ...
of the genus. The generic name combines that of ''Ornithomimus'' with a Greek ἀρχαῖος (''archaios''), "ancient", because Russell believed that the layers in which ''Archaeornithomimus'' was found dated to the
Cenomanian The Cenomanian is, in the ICS' geological timescale, the oldest or earliest age of the Late Cretaceous Epoch or the lowest stage of the Upper Cretaceous Series. An age is a unit of geochronology; it is a unit of time; the stage is a unit in the s ...
-
Turonian The Turonian is, in the ICS' geologic timescale, the second age in the Late Cretaceous Epoch, or a stage in the Upper Cretaceous Series. It spans the time between 93.9 ± 0.8 Ma and 89.8 ± 1 Ma (million years ago). The Turonian is preceded b ...
ages, about 95 million years ago, making it one of the oldest ornithomimids known at the time. Gilmore had not assigned a
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 ...
specimen; in 1990 David Smith and
Peter Galton Peter Malcolm Galton (born 14 March 1942 in London) is a British vertebrate paleontologist who has to date written or co-written about 190 papers in scientific journals or chapters in paleontology textbooks, especially on ornithischian and prosa ...
in the first comprehensive description of the fossils, choose specimen AMNH 6565, a foot, as the
lectotype In biology, a type is a particular specimen (or in some cases a group of specimens) of an organism to which the scientific name of that organism is formally attached. In other words, a type is an example that serves to anchor or centralizes the ...
. The fossils were found in the
Iren Dabasu Formation The Iren Dabasu Formation (also known as Erlian Formation) is a Late Cretaceous geologic formation in the Iren Nor region of Inner Mongolia. Dinosaur remains diagnostic to the genus level are among the fossils that have been recovered from the fo ...
, which has been dated to the Cenomanian age, around 95.8 ± 6.2
million years ago The abbreviation Myr, "million years", is a unit of a quantity of (i.e. ) years, or 31.556926 teraseconds. Usage Myr (million years) is in common use in fields such as Earth science and cosmology. Myr is also used with Mya (million years ago). ...
. Foot bones found in the
Early Cretaceous The Early Cretaceous ( geochronological name) or the Lower Cretaceous (chronostratigraphic name), is the earlier or lower of the two major divisions of the Cretaceous. It is usually considered to stretch from 145  Ma to 100.5 Ma. Geology Pro ...
Arundel Formation The Arundel Formation, also known as the Arundel Clay, is a clay-rich sedimentary rock formation, within the Potomac Group, found in Maryland of the United States of America. It is of Aptian age (Lower Cretaceous). This rock unit had been econ ...
of
Maryland Maryland ( ) is a state in the Mid-Atlantic region of the United States. It shares borders with Virginia, West Virginia, and the District of Columbia to its south and west; Pennsylvania to its north; and Delaware and the Atlantic Ocean to ...
were referred by
Othniel Charles Marsh Othniel Charles Marsh (October 29, 1831 – March 18, 1899) was an American professor of Paleontology in Yale College and President of the National Academy of Sciences. He was one of the preeminent scientists in the field of paleontology. Among h ...
to '' Allosaurus medius'' in 1888. In 1911
Richard Swann Lull Richard Swann Lull (November 6, 1867 – April 22, 1957) was an American paleontologist and Sterling Professor at Yale University who is largely remembered now for championing a non-Darwinian view of evolution, whereby mutation(s) could unl ...
named these as a new species of ''
Dryptosaurus ''Dryptosaurus'' ( ) is a genus of tyrannosauroid that lived approximately 67 million years ago (mya) during the latter part of the Cretaceous period, New Jersey. ''Dryptosaurus'' was a large, bipedal, ground-dwelling carnivore, that grow up to ...
'': ''Dryptosaurus grandis''. In 1920 Gilmore renamed them to a new species of ''Ornithomimus''. However, because ''Ornithomimus grandis'' already existed, he renamed the species ''Ornithomimus affinis''. In 1972 Dale Russell renamed them as a second species of ''Archaeornithomimus'': ''Archaeornithomimus affinis''. However, in 1990 Smith and Galton concluded that the remains were not ornithomimosaurian and came from some other small theropod. In 1995 a supposed third species of ''Archaeornithomimus'' was named by Lev A. Nesov: ''Archaeornithomimus bissektensis'', based on the holotype N 479/12457, a
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 ...
and
metatarsals The metatarsal bones, or metatarsus, are a group of five long bones in the foot, located between the tarsal bones of the hind- and mid-foot and the phalanges of the toes. Lacking individual names, the metatarsal bones are numbered from the medi ...
of a juvenile, found in the
Bissekty Formation The Bissekty Formation (sometimes referred to as Bissekt) is a geologic formation and Lagerstätte which crops out in the Kyzyl Kum desert of Uzbekistan, and dates to the Late Cretaceous Period. Laid down in the mid to late Turonian, it is dated ...
of
Uzbekistan Uzbekistan (, ; uz, Ozbekiston, italic=yes / , ; russian: Узбекистан), officially the Republic of Uzbekistan ( uz, Ozbekiston Respublikasi, italic=yes / ; russian: Республика Узбекистан), is a doubly landlocked cou ...
, dating to the
Turonian The Turonian is, in the ICS' geologic timescale, the second age in the Late Cretaceous Epoch, or a stage in the Upper Cretaceous Series. It spans the time between 93.9 ± 0.8 Ma and 89.8 ± 1 Ma (million years ago). The Turonian is preceded b ...
-
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 t ...
. Nevertheless, the affinity of ''A. bissektensis'' is generally doubted or not mentioned.


Description

''Archaeornithomimus'' was a medium sized ornithomimosaur, reaching long with a weight ranging from . Solid evidence coming from other ornithomimosaurian relatives suggest that ''Archaeornithomimus'' was a feathered animal, with very
ratite A ratite () is any of a diverse group of flightless, large, long-necked, and long-legged birds of the infraclass Palaeognathae. Kiwi, the exception, are much smaller and shorter-legged and are the only nocturnal extant ratites. The systematics ...
-like feathers and equipped with a keratinous beak. The hindlimbs were robustly built. The third
metatarsal The metatarsal bones, or metatarsus, are a group of five long bones in the foot, located between the tarsal bones of the hind- and mid-foot and the phalanges of the toes. Lacking individual names, the metatarsal bones are numbered from the med ...
was not pinched at the upper end, so the foot was not arctometatarsalian. The
cervical vertebrae In tetrapods, cervical vertebrae (singular: 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 ...
are highly pneumatized with very complex internal chambers across the
neural arches The spinal column, a defining synapomorphy shared by nearly all vertebrates,Hagfish are believed to have secondarily lost their spinal column is a moderately flexible series of vertebrae (singular vertebra), each constituting a characteristic ...
and the
centrum (Latin for ''center'') may refer to: Places In Greenland * Nuuk Centrum, a district of Nuuk, Greenland * Centrum Lake, Greenland In the Netherlands * Amsterdam-Centrum, the inner-most borough of Amsterdam, Netherlands * Rotterdam Centrum, a borou ...
(body of the vertebra), indicating the presence of cervical
air sacs Air sacs are spaces within an organism where there is the constant presence of air. Among modern animals, birds possess the most air sacs (9–11), with their extinct dinosaurian relatives showing a great increase in the pneumatization (presence ...
. The anterior
dorsal Dorsal (from Latin ''dorsum'' ‘back’) may refer to: * Dorsal (anatomy), an anatomical term of location referring to the back or upper side of an organism or parts of an organism * Dorsal, positioned on top of an aircraft's fuselage * Dorsal c ...
and some
caudal vertebrae The spinal column, a defining synapomorphy shared by nearly all vertebrates,Hagfish are believed to have secondarily lost their spinal column is a moderately flexible series of vertebrae (singular vertebra), each constituting a characteristic ...
features some degree of pneumacity, however, the
sacral vertebrae The sacrum (plural: ''sacra'' or ''sacrums''), in human anatomy, is a large, triangular bone at the base of the spine that forms by the fusing of the sacral vertebrae (S1S5) between ages 18 and 30. The sacrum situates at the upper, back part ...
are apneumatic. In a 2001 study conducted by Bruce Rothschild and other paleontologists, 229 foot bones referred to ''Archaeornithomimus'' were examined for signs of
stress fracture A stress fracture is a fatigue-induced bone fracture caused by repeated stress over time. Instead of resulting from a single severe impact, stress fractures are the result of accumulated injury from repeated submaximal loading, such as running or ...
, but none were found.


Classification

Russell assigned ''Archaeornithomimus'' to the
Ornithomimidae Ornithomimidae (meaning "bird-mimics") is a family of theropod dinosaurs which bore a superficial resemblance to modern ostriches. Ornithomimids were fast, omnivorous or herbivorous dinosaurs known mainly from the Late Cretaceous Period of Lauras ...
. Recent
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 ...
analyses either confirm this or recover the species outside of the Ornithomimidae, basal in the
Ornithomimosauria Ornithomimosauria ("bird-mimic lizards") are theropod dinosaurs which bore a superficial resemblance to the modern-day ostrich. They were fast, omnivorous or herbivorous dinosaurs from the Cretaceous Period of Laurasia (now Asia, Europe and Nor ...
. During the description of ''
Hesperornithoides ''Hesperornithoides'' (meaning "western bird form"; nicknamed "Lori") is a genus of troodontid theropod dinosaur that lived in North America during the Late Jurassic period. Discovery Although several Troodontid teeth were found, with the trood ...
'', an extensive
Coelurosauria Coelurosauria (; from Greek, meaning "hollow tailed lizards") is the clade containing all theropod dinosaurs more closely related to birds than to carnosaurs. Coelurosauria is a subgroup of theropod dinosaurs that includes compsognathids, t ...
phylogenetic analysis (also known as the Lori matrix) was conducted in order to determine the position of this paravian. Here, ''Archaeornithomimus'' was recovered within the Garudimimidae being a relative of ''
Arkansaurus ''Arkansaurus'' (meaning "Arkansas lizard") is an extinct genus of ornithomimosaurian theropod dinosaur. It lived during the Albian and Aptian stages of the Early Cretaceous. The type and only species is ''Arkansaurus fridayi''. History In Au ...
'':


Paleoecology

The remains of ''Archaeornithomimus'' were found in the
Iren Dabasu Formation The Iren Dabasu Formation (also known as Erlian Formation) is a Late Cretaceous geologic formation in the Iren Nor region of Inner Mongolia. Dinosaur remains diagnostic to the genus level are among the fossils that have been recovered from the fo ...
, which dates back to the
Cenomanian The Cenomanian is, in the ICS' geological timescale, the oldest or earliest age of the Late Cretaceous Epoch or the lowest stage of the Upper Cretaceous Series. An age is a unit of geochronology; it is a unit of time; the stage is a unit in the s ...
stage about 96 million years ago during 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 ...
period. The environments present on the formation were mainly large
floodplain A floodplain or flood plain or bottomlands is an area of land adjacent to a river which stretches from the banks of its channel to the base of the enclosing valley walls, and which experiences flooding during periods of high discharge.Goudi ...
terrains with
braided rivers A braided river, or braided channel, consists of a network of river channels separated by small, often temporary, islands called braid bars or, in English usage, ''aits'' or ''eyots''. Braided streams tend to occur in rivers with high sediment lo ...
and
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) and deposits sediments on an inner, convex bank ...
that were connected to the ocean, supporting extensive vegetation as seen on the palaeosol development and the numerous remains from
herbivorous A herbivore is an animal anatomically and physiologically adapted to eating plant material, for example foliage or marine algae, for the main component of its diet. As a result of their plant diet, herbivorous animals typically have mouthpart ...
dinosaurs such as hadrosauroids. Like other members of the Ornithomimosauria, ''Archaeornithomimus'' was likely an
omnivore An omnivore () is an animal that has the ability to eat and survive on both plant and animal matter. Obtaining energy and nutrients from plant and animal matter, omnivores digest carbohydrates, protein, fat, and fiber, and metabolize the nutr ...
equipped with a horny beak, eating everything from small mammals, to plants and fruit, to eggs, and even hatchlings of other Asian dinosaurs. Other dinosaurs that co-existed with ''Archaeornithomimus'' in the formation included other theropods, such as ''
Alectrosaurus ''Alectrosaurus'' (; meaning "alone lizard") is a genus of tyrannosauroid theropod dinosaur that lived in Asia during the Late Cretaceous period, about some 96 million years ago in what is now the Iren Dabasu Formation. It was a medium-sized, ...
'', ''
Erliansaurus ''Erliansaurus'' (meaning "Erlian lizard") is a genus of therizinosaur theropod dinosaur that lived in Asia during the Cenomanian stage of the Late Cretaceous period in what is now Nei Mongol, Iren Dabasu Formation. Discovery and naming The r ...
'', ''
Gigantoraptor ''Gigantoraptor'' () is a genus of large oviraptorosaur dinosaur that lived in Asia during the Late Cretaceous period. It is known from the Iren Dabasu Formation of Inner Mongolia, where the first remains were found in 2005. ''Gigantoraptor'' wa ...
'' and ''
Neimongosaurus ''Neimongosaurus'' (meaning "Nei Mongol lizard") is a genus of herbivorous therizinosaur theropod dinosaur that lived in Asia during the Cenomanian stage of the Late Cretaceous period in what is now the Iren Dabasu Formation. Discovery and nami ...
''. Herbivorous dinosaurs were represented by ''
Bactrosaurus ''Bactrosaurus'' (; meaning "Club lizard," "baktron" = club + ''sauros'' = lizard) is a genus of herbivorous hadrosauroid dinosaur that lived in Asia during the Late Cretaceous, about 96-85 million years ago. The position ''Bactrosaurus'' occupi ...
'', ''
Gilmoreosaurus ''Gilmoreosaurus'' (meaning "Charles Whitney Gilmore's lizard") is the name given to a genus of dinosaur from the Cretaceous of Asia. The type species is ''Gilmoreosaurus mongoliensis''. It is believed to be a hadrosaur or iguanodont from the Ire ...
'' and ''
Sonidosaurus ''Sonidosaurus'' (meaning "Sonid lizard", after Sonid, the large geographical area that includes the type locality ) is a genus of sauropod dinosaur from the Late Cretaceous. It was a titanosaur which lived in what is now Inner Mongolia. The typ ...
''.


See also

* Timeline of ornithomimosaur research *
Glossary of dinosaur anatomy This glossary explains technical terms commonly employed in the description of dinosaur body fossils. Besides dinosaur-specific terms, it covers terms with wider usage, when these are of central importance in the study of dinosaurs or when their ...


References

{{Taxonbar, from=Q131707 Ornithomimids Late Cretaceous dinosaurs of Asia Fossils of Uzbekistan Bissekty Formation Fossil taxa described in 1972 Taxa named by Dale Russell