Archaeornithomimus
   HOME

TheInfoList



OR:

''Archaeornithomimus'' (meaning "ancient bird mimic") is a
genus Genus (; : genera ) is a taxonomic rank above species and below family (taxonomy), family as used in the biological classification of extant taxon, living and fossil organisms as well as Virus classification#ICTV classification, viruses. In bino ...
of ornithomimosaurian
theropod Theropoda (; from ancient Greek , (''therion'') "wild beast"; , (''pous, podos'') "foot"">wiktionary:ποδός"> (''pous, podos'') "foot" is one of the three major groups (clades) of dinosaurs, alongside Ornithischia and Sauropodom ...
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 ...
period, around 96 million years ago in the Iren Dabasu Formation.


Discovery and naming

In 1923, during 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 ...
expedition by
Roy Chapman Andrews Roy Chapman Andrews (January 26, 1884 – March 11, 1960) was an American explorer, adventurer, and Natural history, naturalist who became the director of the American Museum of Natural History. He led a series of expeditions through the politi ...
to
Inner Mongolia Inner Mongolia, officially the Inner Mongolia Autonomous Region, is an Autonomous regions of China, autonomous region of China. Its border includes two-thirds of the length of China's China–Mongolia border, border with the country of Mongolia. ...
, 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 in 1933 as a new species of '' Ornithomimus'': ''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 at ...
in 1972, making ''Archaeornithomimus asiaticus'' the
type species In International_Code_of_Zoological_Nomenclature, 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 spe ...
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 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 ...
-
Turonian The Turonian is, in the International Commission on Stratigraphy, ICS' geologic timescale, the second age (geology), age in the Late Cretaceous epoch (geology), Epoch, or a stage (stratigraphy), stage in the Upper Cretaceous series (stratigraphy), ...
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 (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 ...
specimen; in 1990, David Smith and Peter Galton 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 associated. In other words, a type is an example that serves to anchor or centralizes ...
. The fossils were found in the Iren Dabasu Formation, which has been dated to the Cenomanian age, around 95.8 ± 6.2
million years ago Million years ago, abbreviated as Mya, Myr (megayear) or Ma (megaannum), is a unit of time equal to (i.e. years), or approximately 31.6 teraseconds. Usage Myr is in common use in fields such as Earth science and cosmology. Myr is also used w ...
.


Formerly assigned species

Foot bones found in the
Early Cretaceous The Early Cretaceous (geochronology, geochronological name) or the Lower Cretaceous (chronostratigraphy, chronostratigraphic name) is the earlier or lower of the two major divisions of the Cretaceous. It is usually considered to stretch from 143.1 ...
Arundel Formation of
Maryland Maryland ( ) is a U.S. state, state in the Mid-Atlantic (United States), Mid-Atlantic region of the United States. It borders the states of Virginia to its south, West Virginia to its west, Pennsylvania to its north, and Delaware to its east ...
were referred by
Othniel Charles Marsh Othniel Charles Marsh (October 29, 1831 – March 18, 1899) was an American professor of paleontology. A prolific fossil collector, Marsh was one of the preeminent paleontologists of the nineteenth century. Among his legacies are the discovery or ...
to '' Allosaurus medius'' in 1888. In 1911, Richard Swann Lull named these as a new species of '' Dryptosaurus'': ''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'' (''A. affinis''), but other authors considered this taxon a ''
nomen dubium In binomial nomenclature, a ''nomen dubium'' (Latin for "doubtful name", plural ''nomina dubia'') is a scientific name that is of unknown or doubtful application. Zoology In case of a ''nomen dubium,'' it may be impossible to determine whether a ...
'' in both editions of
The Dinosauria ''The Dinosauria'' is an encyclopedia on dinosaurs, edited by paleontologists David B. Weishampel, Peter Dodson, and Halszka Osmólska. It has been published in two editions by the University of California Press, with the first edition in 1990 ...
. In 1990, Smith and Galton concluded that the remains were not ornithomimosaurian and came from some other small theropod, while the describers of other ornithomimosaurs ('' Kinnareemimus'', '' Arkansaurus'' and '' Paraxenisaurus'') suggested that "''O.''" ''affinis'' does belong to an indeterminate ornithomimosaur. In 1995, Nesov named a new species of ornithomimosaur from the
Bissekty Formation The Bissekty Formation (sometimes referred to as Bissekt) is a formation (geology), geologic formation and Lagerstätte which outcrop, crops out in the Kyzyl Kum desert of Uzbekistan, and dates to the Late Cretaceous Period (geology), Period. Laid ...
(
Turonian The Turonian is, in the International Commission on Stratigraphy, ICS' geologic timescale, the second age (geology), age in the Late Cretaceous epoch (geology), Epoch, or a stage (stratigraphy), stage in the Upper Cretaceous series (stratigraphy), ...
) of
Uzbekistan , image_flag = Flag of Uzbekistan.svg , image_coat = Emblem of Uzbekistan.svg , symbol_type = Emblem of Uzbekistan, Emblem , national_anthem = "State Anthem of Uzbekistan, State Anthem of the Republ ...
as ''Archaeornithomimus bissektensis'', based on the holotype N 479/12457, a
femur The femur (; : femurs or femora ), or thigh bone is the only long bone, bone in the thigh — the region of the lower limb between the hip and the knee. In many quadrupeds, four-legged animals the femur is the upper bone of the hindleg. The Femo ...
of a juvenile, along with other referred specimens including the metatarsals. However, the affinity of ''A. bissektensis'' was generally doubted or not mentioned by subsequent studies. In 2025, Averianov and Sues assigned this taxon to the new genus '' Dzharacursor''.


Description

''Archaeornithomimus'' was a medium sized ornithomimosaur, reaching long and weighing over . Solid evidence coming from other ornithomimosaurian relatives suggest that ''Archaeornithomimus'' was a feathered animal, with very
ratite Ratites () are a polyphyletic group consisting of all birds within the infraclass Palaeognathae that lack keels and cannot fly. They are mostly large, long-necked, and long-legged, the exception being the kiwi, which is also the only nocturnal ...
-like feathers and equipped with a keratinous beak. The hindlimbs were robustly built. The third
metatarsal The metatarsal bones or metatarsus (: metatarsi) are a group of five long bones in the midfoot, located between the tarsal bones (which form the heel and the ankle) and the phalanges ( toes). Lacking individual names, the metatarsal bones are ...
was not pinched at the upper end, so the foot was not arctometatarsalian. The
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 ...
are highly pneumatized with very complex internal chambers across the neural arches and the centrum (body of the vertebra), indicating the presence of cervical air sacs. 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 The fus ...
and some
caudal vertebrae Caudal vertebrae are the vertebrae of the tail in many vertebrates. In birds, the last few caudal vertebrae fuse into the pygostyle, and in apes, including humans, the caudal vertebrae are fused into the coccyx. In many reptiles, some of the caud ...
features some degree of pneumacity, however, the sacral vertebrae 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, but none were found.


Classification

Russell assigned ''Archaeornithomimus'' to the Ornithomimidae. Recent
cladistic Cladistics ( ; from Ancient Greek 'branch') 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 ...
analyses either confirm this or recover the species outside of the Ornithomimidae, basal in the Ornithomimosauria. During the description of '' Hesperornithoides'', 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, tyra ...
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'':


Paleoecology

The remains of ''Archaeornithomimus'' were found in the Iren Dabasu Formation, which dates back to the
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 ...
stage about 96 million years ago 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 ...
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. Floodplains stretch from the banks of a river channel to the base of the enclosing valley, and experience flooding during periods of high Discharge (hydrolog ...
terrains with braided rivers 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 or river cliff) and deposits sediments on an inn ...
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 evolved to feed on plants, especially upon vascular tissues such as foliage, fruits or seeds, as the main component of its diet. These more broadly also encompass animals that eat n ...
dinosaurs such as hadrosauroids. Like other members of the Ornithomimosauria, ''Archaeornithomimus'' was likely an
omnivore An omnivore () is an animal that regularly consumes significant quantities of both plant and animal matter. Obtaining energy and nutrients from plant and animal matter, omnivores digest carbohydrates, protein, fat, and fiber, and metabolize t ...
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'', '' Erliansaurus'', ''
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'' w ...
'' and '' Neimongosaurus''. Herbivorous dinosaurs were represented by '' Bactrosaurus'', '' Gilmoreosaurus'' and '' Sonidosaurus''.


See also

* Timeline of ornithomimosaur research * Glossary of dinosaur anatomy


References

{{Taxonbar, from=Q131707 Ornithomimidae Dinosaur genera Cenomanian dinosaurs Dinosaurs of China Fossil taxa described in 1972 Taxa named by Dale Russell