Anserimimus
Encyclopedia
Anserimimus is a genus
of ornithomimid theropod dinosaur
, from the Late Cretaceous
Period of what is now Mongolia
. It was a lanky, fast-running
animal, possibly an omnivore
. From what fossil
s are known, it probably closely resembled other ornithomimids, except for its more powerful forelimbs.
, or province, of Bayankhongor during a joint Soviet-Mongolian expedition to the Gobi Desert
, in the late 1970s.
Mongolian paleontologist Rinchen Barsbold named Anserimimus in 1988, combining the Latin
anser meaning 'goose' with the Greek
mimos meaning 'mimic'. Anser is the generic name of several species of geese. Although Anserimimus does not specifically resemble a goose, ornithomimosaurs have traditionally been named after different types of birds, such as Struthiomimus
('ostrich mimic'), Gallimimus
('rooster mimic'), and Pelecanimimus
('pelican mimic'). The one named species of Anserimimus is called Anserimimus planinychus. The specific name is derived from the Latin planus meaning 'flat', and the Ancient Greek ὄνυξ, onyx, meaning 'claw', in reference to the peculiar flattened claws which characterize the genus.
Anserimimus was recovered from the Nemegt Formation
of Mongolia
. The Nemegt is thought to represent alluvial plain
s containing meander
ing river
s. The layer Anserimimus was found, is dating from the early Maastrichtian
stage of the Late Cretaceous
, or about 70 million years ago.
There is only a single specimen of Anserimimus, its holotype
IGM 100/300. It consists of a rather complete and articulated skeleton lacking the skull and lower jaws. Limited information has been published on the anatomy of Anserimimus, as Barsbold did not describe most of these bones, instead focusing on only those with features that set Anserimimus apart from other ornithomimids. In an unpublished thesis Robert Bronowicz in 2005 gave a detailed description of the species, also referring additional material to it, among which a second partial skeleton, specimen ZPAL MgD-I/65. However, in 2010 Bronowicz concluded this other find, though most closely related to Anserimimus planinychus, probably represented a separate taxon
.
in 2010 estimated its length at three metres, its weight at fifty kilogrammes. The thighbone is 435 millimetres long.
There are several key differences between it and related species, though most of these are shared with ZPAL MgD-I/65. The claws on the hand are long, low at the back and rather straight, only slightly curved, with the lower surface nearly flat. The forelimb is long and also built more powerfully than that of other ornithomimids, with large crests on the scapulocoracoid
of the shoulder and humerus
(upper arm bone), which provided attachment points for large arm muscles like the biceps
. The metacarpus of the hand is fused, adding to the strength. The foot is strongly arctometatarsalian, with the third metatarsal excluded from the front surface of the metatarsus
over 40% of its upper length.
Ornithomimosauria
. This has been confirmed by modern cladistic analysis. Its closest relative may be Gallimimus from the same formation albeit from a different area (Kobayashi & Lu, 2003; Kobayashi & Barsbold, 2005). Other studies have been unable specifically to determine its relationships or those of any other ornithomimids (Ji et al., 2003; Makovicky et al., 2004).
and Deinocheirus
, as well as smaller dromaeosaurids, oviraptorosaurs, troodontids, and bird
s. Herbivore
s are represented by the hadrosaurid
s Barsboldia
and Saurolophus
, the ankylosaurid Tarchia
and several titanosaurian sauropods and pachycephalosauria
ns.
The function of the powerful arm, with its straightened claws, remains unknown. It may indicate a different diet or food-gathering strategy than other ornithomimids, although its diet is difficult to determine, since the animal's skull is unknown. Scientists have long hypothesized
that ornithomimids, descended from carnivorous
theropod ancestors, were actually omnivores or even herbivore
s (Osborn, 1916).
Genus
In biology, a genus is a low-level taxonomic rank used in the biological classification of living and fossil organisms, which is an example of definition by genus and differentia...
of ornithomimid theropod dinosaur
Dinosaur
Dinosaurs are a diverse group of animals of the clade and superorder Dinosauria. They were the dominant terrestrial vertebrates for over 160 million years, from the late Triassic period until the end of the Cretaceous , when the Cretaceous–Paleogene extinction event led to the extinction of...
, from the Late Cretaceous
Cretaceous
The Cretaceous , derived from the Latin "creta" , usually abbreviated K for its German translation Kreide , is a geologic period and system from circa to million years ago. In the geologic timescale, the Cretaceous follows the Jurassic period and is followed by the Paleogene period of the...
Period of what is now Mongolia
Mongolia
Mongolia is a landlocked country in East and Central Asia. It is bordered by Russia to the north and China to the south, east and west. Although Mongolia does not share a border with Kazakhstan, its western-most point is only from Kazakhstan's eastern tip. Ulan Bator, the capital and largest...
. It was a lanky, fast-running
Cursorial
Cursorial is a biological term that describes an organism as being adapted specifically to run. It is typically used in conjunction with an animal's feeding habits or another important adaptation. For example, a horse can be considered a "cursorial grazer", while a wolf may be considered a...
animal, possibly an omnivore
Omnivore
Omnivores are species that eat both plants and animals as their primary food source...
. From what fossil
Fossil
Fossils are the preserved remains or traces of animals , plants, and other organisms from the remote past...
s are known, it probably closely resembled other ornithomimids, except for its more powerful forelimbs.
Discovery
Anserimimus was found in the Mongolian aimagAimags of Mongolia
Mongolia is divided into 21 aimags . Each aimag is subdivided into several sums. The name aimag is derived from the Mongolian and Turkic languages word for "tribe". The modern aimags were established since 1921...
, or province, of Bayankhongor during a joint Soviet-Mongolian expedition to the Gobi Desert
Gobi Desert
The Gobi is a large desert region in Asia. It covers parts of northern and northwestern China, and of southern Mongolia. The desert basins of the Gobi are bounded by the Altai Mountains and the grasslands and steppes of Mongolia on the north, by the Hexi Corridor and Tibetan Plateau to the...
, in the late 1970s.
Mongolian paleontologist Rinchen Barsbold named Anserimimus in 1988, combining the Latin
Latin
Latin is an Italic language originally spoken in Latium and Ancient Rome. It, along with most European languages, is a descendant of the ancient Proto-Indo-European language. Although it is considered a dead language, a number of scholars and members of the Christian clergy speak it fluently, and...
anser meaning 'goose' with the Greek
Ancient Greek
Ancient Greek is the stage of the Greek language in the periods spanning the times c. 9th–6th centuries BC, , c. 5th–4th centuries BC , and the c. 3rd century BC – 6th century AD of ancient Greece and the ancient world; being predated in the 2nd millennium BC by Mycenaean Greek...
mimos meaning 'mimic'. Anser is the generic name of several species of geese. Although Anserimimus does not specifically resemble a goose, ornithomimosaurs have traditionally been named after different types of birds, such as Struthiomimus
Struthiomimus
Struthiomimus is a genus of ornithomimid dinosaur from the late Cretaceous of Alberta, Canada. It was a long-legged, ostrich-like dinosaur.The bipedal Struthiomimus stood about long and tall at the hips and weighed around...
('ostrich mimic'), Gallimimus
Gallimimus
Gallimimus is a genus of ornithomimid theropod dinosaur from the late Cretaceous period Nemegt Formation of Mongolia. With individuals as long as , it was one of the largest ornithomimosaurs...
('rooster mimic'), and Pelecanimimus
Pelecanimimus
Pelecanimimus is a genus of basal ornithomimosaurian theropod dinosaur from the Early Cretaceous of Spain...
('pelican mimic'). The one named species of Anserimimus is called Anserimimus planinychus. The specific name is derived from the Latin planus meaning 'flat', and the Ancient Greek ὄνυξ, onyx, meaning 'claw', in reference to the peculiar flattened claws which characterize the genus.
Anserimimus was recovered from the Nemegt Formation
Nemegt Formation
The Nemegt Formation is a geological formation dating from the Late Cretaceous sedimentary from the Gobi Desert of Mongolia. It overlies and sometimes forms folds with the Barun Goyot Formation. It consists of river channel sediments and contains fossils of fish, turtles, crocodilians, birds and a...
of Mongolia
Mongolia
Mongolia is a landlocked country in East and Central Asia. It is bordered by Russia to the north and China to the south, east and west. Although Mongolia does not share a border with Kazakhstan, its western-most point is only from Kazakhstan's eastern tip. Ulan Bator, the capital and largest...
. The Nemegt is thought to represent alluvial plain
Alluvial plain
An alluvial plain is a relatively flat landform created by the deposition of sediment over a long period of time by one or more rivers coming from highland regions, from which alluvial soil forms...
s containing meander
Meander
A meander in general is a bend in a sinuous watercourse. A meander is formed when the moving water in a stream erodes the outer banks and widens its valley. A stream of any volume may assume a meandering course, alternately eroding sediments from the outside of a bend and depositing them on the...
ing river
River
A river is a natural watercourse, usually freshwater, flowing towards an ocean, a lake, a sea, or another river. In a few cases, a river simply flows into the ground or dries up completely before reaching another body of water. Small rivers may also be called by several other names, including...
s. The layer Anserimimus was found, is dating from the early Maastrichtian
Maastrichtian
The Maastrichtian is, in the ICS' geologic timescale, the latest age or upper stage of the Late Cretaceous epoch or Upper Cretaceous series, the Cretaceous period or system, and of the Mesozoic era or erathem. It spanned from 70.6 ± 0.6 Ma to 65.5 ± 0.3 Ma...
stage of the Late Cretaceous
Late Cretaceous
The Late Cretaceous is the younger of two epochs into which the Cretaceous period is divided in the geologic timescale. Rock strata from this epoch form the Upper Cretaceous series...
, or about 70 million years ago.
There is only a single specimen of Anserimimus, its holotype
Holotype
A holotype is a single physical example of an organism, known to have been used when the species was formally described. It is either the single such physical example or one of several such, but explicitly designated as the holotype...
IGM 100/300. It consists of a rather complete and articulated skeleton lacking the skull and lower jaws. Limited information has been published on the anatomy of Anserimimus, as Barsbold did not describe most of these bones, instead focusing on only those with features that set Anserimimus apart from other ornithomimids. In an unpublished thesis Robert Bronowicz in 2005 gave a detailed description of the species, also referring additional material to it, among which a second partial skeleton, specimen ZPAL MgD-I/65. However, in 2010 Bronowicz concluded this other find, though most closely related to Anserimimus planinychus, probably represented a separate taxon
Taxon
|thumb|270px|[[African elephants]] form a widely-accepted taxon, the [[genus]] LoxodontaA taxon is a group of organisms, which a taxonomist adjudges to be a unit. Usually a taxon is given a name and a rank, although neither is a requirement...
.
Description
Anserimimus was a medium-sized ornithomimosaurian. Gregory S. PaulGregory S. Paul
Gregory Scott Paul is a freelance researcher, author and illustrator who works in paleontology, and more recently has examined sociology and theology. He is best known for his work and research on theropod dinosaurs and his detailed illustrations, both live and skeletal...
in 2010 estimated its length at three metres, its weight at fifty kilogrammes. The thighbone is 435 millimetres long.
There are several key differences between it and related species, though most of these are shared with ZPAL MgD-I/65. The claws on the hand are long, low at the back and rather straight, only slightly curved, with the lower surface nearly flat. The forelimb is long and also built more powerfully than that of other ornithomimids, with large crests on the scapulocoracoid
Scapula
In anatomy, the scapula , omo, or shoulder blade, is the bone that connects the humerus with the clavicle ....
of the shoulder and humerus
Humerus
The humerus is a long bone in the arm or forelimb that runs from the shoulder to the elbow....
(upper arm bone), which provided attachment points for large arm muscles like the biceps
Biceps
Biceps may refer to:*Biceps brachii muscle, a muscle located on the inside of the upper arm*Biceps femoris muscle, one of the hamstring muscles of the back of each thigh*Biceps , a point in a metrical pattern...
. The metacarpus of the hand is fused, adding to the strength. The foot is strongly arctometatarsalian, with the third metatarsal excluded from the front surface of the metatarsus
Metatarsus
The metatarsus or metatarsal bones 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 medial side : the first, second, third, fourth, and fifth...
over 40% of its upper length.
Phylogeny
Anserimimus was by Barsbold assigned to the Ornithomimidae, a group of derivedDerived
In phylogenetics, a derived trait is a trait that is present in an organism, but was absent in the last common ancestor of the group being considered. This may also refer to structures that are not present in an organism, but were present in its ancestors, i.e. traits that have undergone secondary...
Ornithomimosauria
Ornithomimosauria
The Ornithomimosauria, ornithomimosaurs or ostrich dinosaurs were theropod dinosaurs which bore a superficial resemblance to modern ostriches. They were fast, omnivorous or herbivorous dinosaurs from the Cretaceous Period of Laurasia...
. This has been confirmed by modern cladistic analysis. Its closest relative may be Gallimimus from the same formation albeit from a different area (Kobayashi & Lu, 2003; Kobayashi & Barsbold, 2005). Other studies have been unable specifically to determine its relationships or those of any other ornithomimids (Ji et al., 2003; Makovicky et al., 2004).
Paleobiology
Aside from Gallimimus, other theropods found in the Nemegt Formation include the gigantic TarbosaurusTarbosaurus
Tarbosaurus is a genus of tyrannosaurid theropod dinosaur that flourished in Asia about 70 million years ago, at the end of the Late Cretaceous Period. Fossils have been recovered in Mongolia, with more fragmentary remains found further afield in parts of China. Although many species have been...
and Deinocheirus
Deinocheirus
Deinocheirus is a genus of large theropod dinosaur, possibly an ornithomimosaurian, which lived in what is now southern Mongolia, during the late Cretaceous Period .-Discovery and naming:...
, as well as smaller dromaeosaurids, oviraptorosaurs, troodontids, and bird
Bird
Birds are feathered, winged, bipedal, endothermic , egg-laying, vertebrate animals. Around 10,000 living species and 188 families makes them the most speciose class of tetrapod vertebrates. They inhabit ecosystems across the globe, from the Arctic to the Antarctic. Extant birds range in size from...
s. Herbivore
Herbivore
Herbivores are organisms that are anatomically and physiologically adapted to eat plant-based foods. Herbivory is a form of consumption in which an organism principally eats autotrophs such as plants, algae and photosynthesizing bacteria. More generally, organisms that feed on autotrophs in...
s are represented by the hadrosaurid
Hadrosaurid
Hadrosaurids or duck-billed dinosaurs are members of the family Hadrosauridae, and include ornithopods such as Edmontosaurus and Parasaurolophus. They were common herbivores in the Upper Cretaceous Period of what are now Asia, Europe and North America. They are descendants of the Upper...
s Barsboldia
Barsboldia
Barsboldia was a genus of large hadrosaurid dinosaur from the early Maastrichtian Nemegt Formation of Ömnogöv', Mongolia. It is known from a partial vertebral column, partial pelvis, and some ribs...
and Saurolophus
Saurolophus
Saurolophus is a genus of large hadrosaurine duckbill that lived about 69.5-68.5 million years ago, in the Late Cretaceous of North America and Asia; it is one of the few genera of dinosaurs known from multiple continents. It is distinguished by a spike-like crest which projects up and back...
, the ankylosaurid Tarchia
Tarchia
Tarchia is a genus of ankylosaurid dinosaur from the late Cretaceous of Mongolia. It is currently the geologically youngest known of all the Asian ankylosaurid dinosaurs and is represented by five or more specimens, including two complete skulls and one nearly complete postcranial skeleton...
and several titanosaurian sauropods and pachycephalosauria
Pachycephalosauria
Pachycephalosauria is a clade of ornithischian dinosaurs. Well-known genera include Pachycephalosaurus, Stegoceras, Stygimoloch, and Dracorex. Most lived during the Late Cretaceous Period, in what is now North America and Asia. They were all bipedal, herbivorous/omnivorous animals with thick skulls...
ns.
The function of the powerful arm, with its straightened claws, remains unknown. It may indicate a different diet or food-gathering strategy than other ornithomimids, although its diet is difficult to determine, since the animal's skull is unknown. Scientists have long hypothesized
Hypothesis
A hypothesis is a proposed explanation for a phenomenon. The term derives from the Greek, ὑποτιθέναι – hypotithenai meaning "to put under" or "to suppose". For a hypothesis to be put forward as a scientific hypothesis, the scientific method requires that one can test it...
that ornithomimids, descended from carnivorous
Carnivore
A carnivore meaning 'meat eater' is an organism that derives its energy and nutrient requirements from a diet consisting mainly or exclusively of animal tissue, whether through predation or scavenging...
theropod ancestors, were actually omnivores or even herbivore
Herbivore
Herbivores are organisms that are anatomically and physiologically adapted to eat plant-based foods. Herbivory is a form of consumption in which an organism principally eats autotrophs such as plants, algae and photosynthesizing bacteria. More generally, organisms that feed on autotrophs in...
s (Osborn, 1916).
External links
- Anserimimus at The Theropod Database