Chirostenotes
Encyclopedia
Chirostenotes is a genus
of oviraptorosaurian dinosaur
from the late Cretaceous
(about 75 million years ago) of Alberta
, Canada
. The type species
is Chirostenotes pergracilis. Some researchers recognize a second species, C. elegans.
or herbivore
, although the beak is not as heavily constructed as in the Asian Oviraptoridae
. It likely ate small reptile
s and mammal
s, as well as plants, eggs and insects.
In 2005 Phil Senter and J. Michael Parrish published a study on the hand function of Chirostenotes and found that its elongated second finger with its unusually straight claw may have been an adaptation to crevice probing. They suggested that Chirostenotes may have fed on soft-bodied prey that could be impaled by the second claw, such as grubs, as well as unarmored amphibian
s, reptiles, and mammals. However, if Chirostenotes possessed the large primary feathers on its second finger that have been found in other oviraptorosaurs such as Caudipteryx
, it would not have been able to engage in such behavior.
Dinosaur Park Formation
of Canada, which has yielded the most dinosaurs of any Canadian formation. The specimens were studied by Lawrence Morris Lambe who deceased however, before being able to formally name them. In 1924, Charles Whitney Gilmore adopted the name he found in Lambe's notes and described and named the type species
Chirostenotes pergracilis. The generic name is derived from Greek cheir, "hand", and stenotes, "narrowness". The specific name means "throughout", per~, "gracile", gracilis, in Latin
. The holotype
is NMC 2367, the pair of hands
Chirostenotes was but the first name assigned. Feet were then found, specimen CMN 8538, and in 1932 Charles Mortram Sternberg
gave them the name Macrophalangia canadensis, meaning 'large toes from Canada'. Sternberg correctly recognized them as part of a meat-eating dinosaur but thought they belonged to an ornithomimid. In 1936, its lower jaws, specimen CMN 8776, were found by Raymond Sternberg near Steveville and in 1940 he gave them the name Caenagnathus
collinsi. The generic name means 'recent jaw' from Greek kainos, "new", and gnathos, "jaw"; the specific name honours William Henry Collins. The toothless jaws were first thought to be those of a bird
.
Slowly the precise relationship between the finds became clear. In 1960 Alexander Wetmore
concluded that Caenagnathus was not a bird but a ornithomimid. In 1969 Edwin Colbert and Dale Russell
suggested that Chirostenotes and Macrophalangia were one and the same animal. In 1976 Halszka Osmólska
described Caenagnathus as an oviraptosaurian. In 1981 the announcement of Elmisaurus
, an Asian form of which both hand and feet had been preserved, showed the soundness of Colbert and Russell's conjecture.
In 1988, a specimen from storage since 1923 was discovered and studied by Philip Currie
and Dale Russell. This fossil helped link the other discoveries into a single dinosaur. Since the first name applied to any of these remains was Chirostenotes, this were the only name that was recognized as valid.
Currie and Russell also addressed the complicating issue of a possible second form being present in the material. In 1933 William Arthur Parks had named Ornithomimus elegans, based on specimen ROM 781, another foot from Alberta. In 1971, Joël Cracraft, still under the assumption Caenagnathus was a bird, had named a second species of Caenagnathus: Caenagnathus sternbergi, based on specimen CMN 2690, a small lower jaw. In 1988 Russell and Currie concluded that these fossils might present a more gracile morph
of Chirostenotes pergracilis. In 1989 however, Currie thought that they represented a separate smaller species, and named this as a second species of the closely related Elmisaurus
: Elmisaurus elegans. In 1997, this was renamed to Chirostenotes elegans by Hans-Dieter Sues
. This remains contentious.
Several larger skeletons from the early Maastrichtian
Horseshoe Canyon Formation
of Alberta and Hell Creek Formation
of Montana
and South Dakota
have been referred to Chirostenotes in the past, though more recent studies concluded that they represent several new species. The Horseshore Canyon formation specimen was renamed Epichirostenotes
in 2011, while the Hell Creek Formation specimens are still being studied. The latter specimens are more complete and of a considerable size: in 2010 Gregory S. Paul
estimated the length of the South Dakotan Hell Creek specimens at 4 metres (13.1 ft), the weight at 350 kilograms (771.6 lb).
In 2007 a cladistic study by Philip Senter cast doubt on the idea that all of the large Dinosaur Park Formation fossils belonged to the same creature: coding the original hand and jaw specimens separately showed that while the Caenagnathus holotype remained in the more basal position in the Caenagnathidae commonly assigned to it, the Chirostenotes pergracilis holotype was placed as an advanced oviraptorosaurian and an oviraptorid
.
Another fossil connected to Chirostenotes is specimen CMN 8776, a set of jaws with strange teeth, which were originally referred by Gilmore to Chirostenotes pergracilis. Now that it is known that Chirostenotes was a toothless oviraptorosaur, the jaws have been renamed Richardoestesia and are from an otherwise unknown dinosaur, likely a dromaeosaurid.
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 oviraptorosaurian 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...
(about 75 million years ago) of Alberta
Alberta
Alberta is a province of Canada. It had an estimated population of 3.7 million in 2010 making it the most populous of Canada's three prairie provinces...
, Canada
Canada
Canada is a North American country consisting of ten provinces and three territories. Located in the northern part of the continent, it extends from the Atlantic Ocean in the east to the Pacific Ocean in the west, and northward into the Arctic Ocean...
. The type species
Type species
In biological nomenclature, a type species is both a concept and a practical system which is used in the classification and nomenclature of animals and plants. The value of a "type species" lies in the fact that it makes clear what is meant by a particular genus name. A type species is the species...
is Chirostenotes pergracilis. Some researchers recognize a second species, C. elegans.
Description
Chirostenotes was characterized by a toothless beak, long arms ending in slender relatively straight claws, long powerful legs with slender toes. In life, the animal was about 2 metres (6.6 ft) long. Chirostenotes was probably an omnivoreOmnivore
Omnivores are species that eat both plants and animals as their primary food source...
or 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...
, although the beak is not as heavily constructed as in the Asian Oviraptoridae
Oviraptoridae
Oviraptoridae is a group of bird-like, herbivorous and omnivorous maniraptoran dinosaurs. Oviraptorids are characterized by their toothless, parrot-like beaks and, in some cases, elaborate crests. They were generally small, measuring between one and two metres long in most cases, though some...
. It likely ate small reptile
Reptile
Reptiles are members of a class of air-breathing, ectothermic vertebrates which are characterized by laying shelled eggs , and having skin covered in scales and/or scutes. They are tetrapods, either having four limbs or being descended from four-limbed ancestors...
s and mammal
Mammal
Mammals are members of a class of air-breathing vertebrate animals characterised by the possession of endothermy, hair, three middle ear bones, and mammary glands functional in mothers with young...
s, as well as plants, eggs and insects.
In 2005 Phil Senter and J. Michael Parrish published a study on the hand function of Chirostenotes and found that its elongated second finger with its unusually straight claw may have been an adaptation to crevice probing. They suggested that Chirostenotes may have fed on soft-bodied prey that could be impaled by the second claw, such as grubs, as well as unarmored amphibian
Amphibian
Amphibians , are a class of vertebrate animals including animals such as toads, frogs, caecilians, and salamanders. They are characterized as non-amniote ectothermic tetrapods...
s, reptiles, and mammals. However, if Chirostenotes possessed the large primary feathers on its second finger that have been found in other oviraptorosaurs such as Caudipteryx
Caudipteryx
Caudipteryx is a genus of peacock-sized theropod dinosaurs that lived in the Aptian age of the early Cretaceous Period . They were feathered and remarkably birdlike in their overall appearance....
, it would not have been able to engage in such behavior.
Taxonomic history
Chirostenotes has a confusing history of discovery and naming. The first fossils of Chirostenotes, a pair of hands, were in 1914 found by George Fryer Sternberg near Little Sandhill Creek in the CampanianCampanian
The Campanian is, in the ICS' geologic timescale, the fifth of six ages of the Late Cretaceous epoch . The Campanian spans the time from 83.5 ± 0.7 Ma to 70.6 ± 0.6 Ma ...
Dinosaur Park Formation
Dinosaur Park Formation
The Dinosaur Park Formation is the uppermost member of the Judith River Group, a major geologic unit in southern Alberta. It was laid down over a period of time between about 76.5 and 75 million years ago. The formation is made up of deposits of a high-sinuosity fluvial system, and is capped...
of Canada, which has yielded the most dinosaurs of any Canadian formation. The specimens were studied by Lawrence Morris Lambe who deceased however, before being able to formally name them. In 1924, Charles Whitney Gilmore adopted the name he found in Lambe's notes and described and named the type species
Type species
In biological nomenclature, a type species is both a concept and a practical system which is used in the classification and nomenclature of animals and plants. The value of a "type species" lies in the fact that it makes clear what is meant by a particular genus name. A type species is the species...
Chirostenotes pergracilis. The generic name is derived from Greek cheir, "hand", and stenotes, "narrowness". The specific name means "throughout", per~, "gracile", gracilis, in 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...
. The 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...
is NMC 2367, the pair of hands
Chirostenotes was but the first name assigned. Feet were then found, specimen CMN 8538, and in 1932 Charles Mortram Sternberg
Charles Mortram Sternberg
Charles M. Sternberg was an American-Canadian fossil collector and paleontologist, son of Charles Hazelius Sternberg.Late in his career, he collected and described Pachyrhinosaurus, Brachylophosaurus, Parksosaurus and Edmontonia...
gave them the name Macrophalangia canadensis, meaning 'large toes from Canada'. Sternberg correctly recognized them as part of a meat-eating dinosaur but thought they belonged to an ornithomimid. In 1936, its lower jaws, specimen CMN 8776, were found by Raymond Sternberg near Steveville and in 1940 he gave them the name Caenagnathus
Caenagnathus
Caenagnathus is a genus of oviraptorosaurian dinosaur from the late Cretaceous . It is known from a single lower jaw, found in the Dinosaur Park Formation of Alberta, Canada.-Taxonomic history:...
collinsi. The generic name means 'recent jaw' from Greek kainos, "new", and gnathos, "jaw"; the specific name honours William Henry Collins. The toothless jaws were first thought to be those of a 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...
.
Slowly the precise relationship between the finds became clear. In 1960 Alexander Wetmore
Alexander Wetmore
Frank Alexander Wetmore was an American ornithologist and avian paleontologist.-Life:Wetmore studied at the University of Kansas...
concluded that Caenagnathus was not a bird but a ornithomimid. In 1969 Edwin Colbert and Dale Russell
Dale Russell
Dale A. Russell is a Canadian geologist/palaeontologist, currently Research Professor at The Department of Marine Earth and Atmospheric Sciences of North Carolina State University...
suggested that Chirostenotes and Macrophalangia were one and the same animal. In 1976 Halszka Osmólska
Halszka Osmólska
Halszka Osmólska was a Polish paleontologist who had specialized in Mongolian dinosaurs.She was born in Poznań. A member of the 1965 and 1970 Polish–Mongolian expeditions to the Gobi Desert, she described many finds from these rocks, often with Teresa Maryańska...
described Caenagnathus as an oviraptosaurian. In 1981 the announcement of Elmisaurus
Elmisaurus
Elmisaurus is an extinct genus of dinosaur from the Late Cretaceous. It was a theropod belonging to the Oviraptorosauria. Its fossils have been found in Asia and North America. It is known from only its feet and hands....
, an Asian form of which both hand and feet had been preserved, showed the soundness of Colbert and Russell's conjecture.
In 1988, a specimen from storage since 1923 was discovered and studied by Philip Currie
Philip Currie
Philip Henry Wodehouse Currie, 1st Baron Currie GCB , known as Sir Philip Currie between 1885 and 1899, was a British diplomat. He was Ambassador to the Ottoman Empire from 1893 to 1898 and Ambassador to Italy from 1898 to 1902.-Background and education:Currie was the son of Raikes Currie, Member...
and Dale Russell. This fossil helped link the other discoveries into a single dinosaur. Since the first name applied to any of these remains was Chirostenotes, this were the only name that was recognized as valid.
Currie and Russell also addressed the complicating issue of a possible second form being present in the material. In 1933 William Arthur Parks had named Ornithomimus elegans, based on specimen ROM 781, another foot from Alberta. In 1971, Joël Cracraft, still under the assumption Caenagnathus was a bird, had named a second species of Caenagnathus: Caenagnathus sternbergi, based on specimen CMN 2690, a small lower jaw. In 1988 Russell and Currie concluded that these fossils might present a more gracile morph
Morph
- Astronomy :* Morphs collaboration, a collaboration that studied the evolution of spiral galaxies using the Magellan and the Hubble Space Telescope- Biology :...
of Chirostenotes pergracilis. In 1989 however, Currie thought that they represented a separate smaller species, and named this as a second species of the closely related Elmisaurus
Elmisaurus
Elmisaurus is an extinct genus of dinosaur from the Late Cretaceous. It was a theropod belonging to the Oviraptorosauria. Its fossils have been found in Asia and North America. It is known from only its feet and hands....
: Elmisaurus elegans. In 1997, this was renamed to Chirostenotes elegans by Hans-Dieter Sues
Hans-Dieter Sues
Hans-Dieter Sues is a German-born paleontologist who is Senior Scientist and Curator of Vertebrate Paleontology at the National Museum of Natural History of the Smithsonian Institution in Washington, DC. He received his education at Johannes Gutenberg-Universität Mainz , University of Alberta, and...
. This remains contentious.
Several larger skeletons 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...
Horseshoe Canyon Formation
Horseshoe Canyon Formation
The Horseshoe Canyon Formation is part of the Edmonton Group and is up to 230m in thickness. It is Late Campanian to Early Maastrichtian in age and is composed of mudstone, sandstone, and carbonaceous shales...
of Alberta and Hell Creek Formation
Hell Creek Formation
The Hell Creek Formation is an intensely-studied division of Upper Cretaceous to lower Paleocene rocks in North America, named for exposures studied along Hell Creek, near Jordan, Montana...
of Montana
Montana
Montana is a state in the Western United States. The western third of Montana contains numerous mountain ranges. Smaller, "island ranges" are found in the central third of the state, for a total of 77 named ranges of the Rocky Mountains. This geographical fact is reflected in the state's name,...
and South Dakota
South Dakota
South Dakota is a state located in the Midwestern region of the United States. It is named after the Lakota and Dakota Sioux American Indian tribes. Once a part of Dakota Territory, South Dakota became a state on November 2, 1889. The state has an area of and an estimated population of just over...
have been referred to Chirostenotes in the past, though more recent studies concluded that they represent several new species. The Horseshore Canyon formation specimen was renamed Epichirostenotes
Epichirostenotes
Epichirostenotes is a genus of oviraptorosaurian dinosaur from the late Cretaceous. Epichirostenotes is known from an incomplete skeleton found in 1923 at the Horseshoe Canyon Formation, in strata dated to about 72 million years ago. It was first named by Robert M. Sullivan, Steven E. Jasinski and...
in 2011, while the Hell Creek Formation specimens are still being studied. The latter specimens are more complete and of a considerable size: in 2010 Gregory S. Paul
Gregory 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...
estimated the length of the South Dakotan Hell Creek specimens at 4 metres (13.1 ft), the weight at 350 kilograms (771.6 lb).
In 2007 a cladistic study by Philip Senter cast doubt on the idea that all of the large Dinosaur Park Formation fossils belonged to the same creature: coding the original hand and jaw specimens separately showed that while the Caenagnathus holotype remained in the more basal position in the Caenagnathidae commonly assigned to it, the Chirostenotes pergracilis holotype was placed as an advanced oviraptorosaurian and an oviraptorid
Oviraptoridae
Oviraptoridae is a group of bird-like, herbivorous and omnivorous maniraptoran dinosaurs. Oviraptorids are characterized by their toothless, parrot-like beaks and, in some cases, elaborate crests. They were generally small, measuring between one and two metres long in most cases, though some...
.
Another fossil connected to Chirostenotes is specimen CMN 8776, a set of jaws with strange teeth, which were originally referred by Gilmore to Chirostenotes pergracilis. Now that it is known that Chirostenotes was a toothless oviraptorosaur, the jaws have been renamed Richardoestesia and are from an otherwise unknown dinosaur, likely a dromaeosaurid.
Synonyms
- Macrophalangia canadensis Sternberg, 1932
- Caenagnathus collinsi Sternberg, 1940
- Ornithomimus elegans Parks, 1933
- Elmisaurus elegans (Parks, 1933) Currie, 1989
- Caenagnathus sternbergi Cracraft, 1971
- Chirostenotes sternbergi (Cracraft, 1971) Eberth & Currie & Brinkman & Ryan & Braman & Gardner & Lam & Spivak & Neuman, 2001