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Coelurosauria (; from Greek, meaning "hollow tailed lizards") is the
clade A clade (), also known as a monophyletic group or natural group, is a group of organisms that are monophyletic – that is, composed of a common ancestor and all its lineal descendants – on a phylogenetic tree. Rather than the English ter ...
containing all theropod
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 ...
s more closely related to
bird Birds are a group of warm-blooded vertebrates constituting the class Aves (), characterised by feathers, toothless beaked jaws, the laying of hard-shelled eggs, a high metabolic rate, a four-chambered heart, and a strong yet lightweig ...
s than to carnosaurs. Coelurosauria is a subgroup of theropod dinosaurs that includes compsognathids, tyrannosaurs,
ornithomimosaurs 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 ...
, and maniraptorans; Maniraptora includes
bird Birds are a group of warm-blooded vertebrates constituting the class Aves (), characterised by feathers, toothless beaked jaws, the laying of hard-shelled eggs, a high metabolic rate, a four-chambered heart, and a strong yet lightweig ...
s, the only known dinosaur group alive today. Most feathered dinosaurs discovered so far have been coelurosaurs.
Philip J. Currie Philip John Currie (born March 13, 1949) is a Canadian palaeontologist and museum curator who helped found the Royal Tyrrell Museum of Palaeontology in Drumheller, Alberta and is now a professor at the University of Alberta in Edmonton. In the ...
had considered it likely and probable that all coelurosaurs were feathered. However, several skin impressions found for some members of this group show pebbly, scaly skin, indicating that feathers did not completely replace scales in all taxa. In the past, Coelurosauria was used to refer to all small theropods, but this classification has since been abolished.


Anatomy


Bodyplan

The studying of anatomical traits in coelurosaurs indicates that the last common ancestor had evolved the ability to eat and digest plant matter, adapting to an omnivorous diet, an ability that could be a major contributor to the clade's success. Later groups would hold on to the omnivory, while others specialized in various directions, becoming insectivorous (
Alvarezsauridae Alvarezsauridae is a family of small, long-legged dinosaurs. Although originally thought to represent the earliest known flightless birds, they are now thought to be an early diverging branch of maniraptoran theropods. Alvarezsaurids were highly ...
), herbivorous (
Therizinosauridae Therizinosauridae (meaning 'scythe lizards')Translated paper
is a family of derived (advanc ...
) and carnivorous (
Tyrannosauroidea Tyrannosauroidea (meaning 'tyrant lizard forms') is a superfamily (or clade) of coelurosaurian theropod dinosaurs that includes the family Tyrannosauridae as well as more basal relatives. Tyrannosauroids lived on the Laurasian supercontin ...
and Dromaeosauridae). The group includes some of the largest (''
Tyrannosaurus ''Tyrannosaurus'' is a genus of large theropoda, theropod dinosaur. The species ''Tyrannosaurus rex'' (''rex'' meaning "king" in Latin), often called ''T. rex'' or colloquially ''T-Rex'', is one of the best represented theropods. ''Tyrannosa ...
'') and smallest (''
Microraptor ''Microraptor'' ( Greek, μικρός, ''mīkros'': "small"; Latin, ''raptor'': "one who seizes") is a genus of small, four-winged dromaeosaurid dinosaurs. Numerous well-preserved fossil specimens have been recovered from Liaoning, China. ...
'', '' Parvicursor'') carnivorous dinosaurs ever discovered. Characteristics that distinguish coelurosaurs include: * a
sacrum 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 o ...
(series of vertebrae that attach to the hips) longer than in other dinosaurs * a tail stiffened towards the tip * a bowed
ulna The ulna (''pl''. ulnae or ulnas) is a long bone found in the forearm that stretches from the elbow to the smallest finger, and when in anatomical position, is found on the medial side of the forearm. That is, the ulna is on the same side of t ...
(lower arm bone). * a
tibia The tibia (; ), also known as the shinbone or shankbone, is the larger, stronger, and anterior (frontal) of the two bones in the leg below the knee in vertebrates (the other being the fibula, behind and to the outside of the tibia); it conn ...
(lower leg bone) that is longer than the
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 ...
(upper leg bone)


Integument

Fossil evidence shows that the skin of even the most primitive coelurosaurs was covered primarily in
feather Feathers are epidermal growths that form a distinctive outer covering, or plumage, on both avian (bird) and some non-avian dinosaurs and other archosaurs. They are the most complex integumentary structures found in vertebrates and a premie ...
s. Fossil traces of feathers, though rare, have been found in members of most major coelurosaurian lineages. Most coelurosaurs also retained scales and scutes on some portion of their bodies, particularly the feet, though some primitive coelurosaurian species are known to have had scales on the upper legs and portions of the tail as well. These include tyrannosauroids, '' Juravenator'', and '' Scansoriopteryx''. Fossils of at least some of these animals (''Scansoriopteryx'' and possibly ''Juravenator'') also preserve feathers elsewhere on the body. Though once thought to be a feature exclusive to coelurosaurs, feathers or feather-like structures are also known in some
ornithischia Ornithischia () is an extinct order of mainly herbivorous dinosaurs characterized by a pelvic structure superficially similar to that of birds. The name ''Ornithischia'', or "bird-hipped", reflects this similarity and is derived from the Greek ...
n dinosaurs (like ''
Tianyulong ''Tianyulong'' (Chinese: 天宇龍; Pinyin: ''tiānyǔlóng''; named for the Shandong Tianyu Museum of Nature where the holotype fossil is housed) is an extinct genus of heterodontosaurid ornithischian dinosaur. The only species is ''T. con ...
'' ''and Kulindadromeus''), and in
pterosaur Pterosaurs (; from Greek ''pteron'' and ''sauros'', meaning "wing lizard") is an extinct clade of flying reptiles in the order, Pterosauria. They existed during most of the Mesozoic: from the Late Triassic to the end of the Cretaceous (228 ...
s. Though it is unknown whether these are related to true feathers, recent analysis has suggested that the feather-like integument found in ornithischians may have evolved independently of coelurosaurs but this was estimated by assuming that primitive pterosaurs had scales. In 2018, two anurognathid specimens were found to have integumentary structures similar to protofeathers. Based on phylogenetic analysis, protofeathers would have had a common origin with avemetatarsalians.


Nervous system and senses

Although rare, complete casts of theropod endocrania are known from fossils. Theropod endocrania can also be reconstructed from preserved braincases without damaging valuable specimens by using a computed tomography scan and 3D reconstruction software. These finds are of evolutionary significance because they help document the emergence of the neurology of modern birds from that of earlier reptiles. An increase in the proportion of the brain occupied by the cerebrum seems to have occurred with the advent of the Coelurosauria and "continued throughout the evolution of maniraptorans and early birds."


Fossil evidence and age

A few fossil traces tentatively associated with the Coelurosauria date back as far as the late
Triassic The Triassic ( ) is a geologic period and system which spans 50.6 million years from the end of the Permian Period 251.902 million years ago ( Mya), to the beginning of the Jurassic Period 201.36 Mya. The Triassic is the first and shortest per ...
. What has been found between then and the earliest
Middle Jurassic The Middle Jurassic is the second Epoch (geology), epoch of the Jurassic Period (geology), Period. It lasted from about 174.1 to 163.5 million years ago. Fossils of land-dwelling animals, such as dinosaurs, from the Middle Jurassic are relatively ...
is fragmentary. The oldest known unambiguous members of Coelurosauria are the
proceratosaurid Proceratosauridae is a family or clade of tyrannosauroid theropod dinosaurs from the Middle Jurassic to the Early Cretaceous. Distinguishing features Unlike the advanced tyrannosaurids but similar to primitive tyrannosauroids like '' Dilong' ...
tyrannosauroids ''
Proceratosaurus ''Proceratosaurus'' is a genus of carnivorous theropod dinosaur from the Middle Jurassic (Bathonian) of England. ''Proceratosaurus'' was a small dinosaur, measuring in length and in body mass.Holtz, Thomas R. Jr. (2008) ''Dinosaurs: The Most ...
'' and '' Kileskus'' from the late Middle Jurassic. Many nearly complete fossil coelurosaurians are known from the
Late Jurassic The Late Jurassic is the third epoch of the Jurassic Period, and it spans the geologic time from 163.5 ± 1.0 to 145.0 ± 0.8 million years ago (Ma), which is preserved in Upper Jurassic strata.Owen 1987. In European lithostratigraphy, the name ...
. ''
Archaeopteryx ''Archaeopteryx'' (; ), sometimes referred to by its German name, "" ( ''Primeval Bird''), is a genus of bird-like dinosaurs. The name derives from the ancient Greek (''archaīos''), meaning "ancient", and (''ptéryx''), meaning "feather" ...
'' (incl. ''
Wellnhoferia ''Wellnhoferia'' (named after Peter Wellnhofer) is a genus of early prehistoric bird-like theropod dinosaur closely related to ''Archaeopteryx''. It lived in what is now Germany, during the Late Jurassic. While ''Wellnhoferia'' was similar to ...
'') is known from Bavaria at 155-150 Ma. '' Ornitholestes'', the troodontid ''
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 ...
'', '' Coelurus fragilis'' and '' Tanycolagreus topwilsoni'' are all known from the
Morrison Formation The Morrison Formation is a distinctive sequence of Upper Jurassic sedimentary rock found in the western United States which has been the most fertile source of dinosaur fossils in North America. It is composed of mudstone, sandstone, siltston ...
in Wyoming at about 150 Ma. '' Epidendrosaurus'' and '' Pedopenna'' are known from the Daohugou Beds in China at about 165-163 Ma. The wide range of fossils in the late Jurassic and morphological evidence shows that coelurosaurian differentiation was virtually complete before the end of the Jurassic. In the early
Cretaceous The Cretaceous ( ) is a geological period that lasted from about 145 to 66 million years ago (Mya). It is the third and final period of the Mesozoic Era, as well as the longest. At around 79 million years, it is the longest geological period of ...
, a superb range of coelurosaurian fossils (including avians) are known from the Yixian Formation in Liaoning. All known theropod dinosaurs from the Yixian Formation are coelurosaurs. Many of the coelurosaurian lineages survived to the end of the Cretaceous period (about 66 Ma) and fossils of some lineages, such as the
Tyrannosauroidea Tyrannosauroidea (meaning 'tyrant lizard forms') is a superfamily (or clade) of coelurosaurian theropod dinosaurs that includes the family Tyrannosauridae as well as more basal relatives. Tyrannosauroids lived on the Laurasian supercontin ...
, are best known from the late Cretaceous. A majority of coelurosaur groups became extinct in the
Cretaceous–Paleogene extinction event The Cretaceous–Paleogene (K–Pg) extinction event (also known as the Cretaceous–Tertiary extinction) was a sudden mass extinction of three-quarters of the plant and animal species on Earth, approximately 66 million years ago. With the ...
, including the Tyrannosauroidea, Ornithomimosauria, Oviraptorosauria, Deinonychosauria,
Enantiornithes The Enantiornithes, also known as enantiornithines or enantiornitheans in literature, are a group of extinct avialans ("birds" in the broad sense), the most abundant and diverse group known from the Mesozoic era. Almost all retained teeth and cla ...
, and Hesperornithes. Only the Neornithes, otherwise known as modern birds, survived, and continued to diversify after the extinction of the other dinosaurs into the numerous forms found today. There is consensus among paleontologists that birds are descended from coelurosaurs. Under modern
cladistical 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 cha ...
definitions, birds are considered the only living lineage of coelurosaurs. Birds are classified by most paleontologists as belonging to the subgroup Maniraptora. A portion of a tail belonging to a juvenile coelurosaur was found in 2015, inside of a piece of amber.


Classification

The
phylogeny A phylogenetic tree (also phylogeny or evolutionary tree Felsenstein J. (2004). ''Inferring Phylogenies'' Sinauer Associates: Sunderland, MA.) is a branching diagram or a tree showing the evolutionary relationships among various biological s ...
and
taxonomy Taxonomy is the practice and science of categorization or classification. A taxonomy (or taxonomical classification) is a scheme of classification, especially a hierarchical classification, in which things are organized into groups or types. ...
of Coelurosauria has been subject to intensive research and revision. For many years, Coelurosauria was a 'dumping ground' for all small theropods. In the 1960s several distinctive lineages of coelurosaurs were recognized, and a number of new infraorders were erected, including the Ornithomimosauria, Deinonychosauria, and Oviraptorosauria. During the 1980s and 1990s, paleontologists began to give Coelurosauria a formal definition, usually as all animals closer to birds than to '' Allosaurus'', or equivalent specifiers. Under this modern definition, many small theropods are not classified as coelurosaurs at all and some large theropods, such as the
tyrannosaurids Tyrannosauridae (or tyrannosaurids, meaning " tyrant lizards") is a family of coelurosaurian theropod dinosaurs that comprises two subfamilies containing up to thirteen genera, including the eponymous '' Tyrannosaurus''. The exact number of ...
, were actually more advanced than allosaurs and therefore were reclassified as giant coelurosaurs. Even more drastically, the segnosaurs, once not even regarded as theropods, have turned out to be non-carnivorous coelurosaurs related to ''
Therizinosaurus ''Therizinosaurus'' (; meaning 'scythe lizard') is a genus of very large therizinosaurid that lived in Asia during the Late Cretaceous period in what is now the Nemegt Formation around 70 million years ago. It contains a single species, ''Theriz ...
''. Senter (2007) listed 59 different published phylogenies since 1984. Those since 2005 have followed almost the same pattern, and differ significantly from many older phylogenies. Within Coelurosauria exists a slightly less inclusive
clade A clade (), also known as a monophyletic group or natural group, is a group of organisms that are monophyletic – that is, composed of a common ancestor and all its lineal descendants – on a phylogenetic tree. Rather than the English ter ...
named Tyrannoraptora. This clade was defined by Sereno (1999) as "'' Tyrannosaurus rex'', '' Passer domesticus'' (the house sparrow), their last common ancestor, and all of its descendants". As tyrannosauroids are considered to be the most basal large group within Coelurosauria, this means that the common ancestor of tyrannosauroids and birds was an even more basal coelurosaurian. As a result, almost all coelurosaurians are also tyrannoraptorans, with the only exceptions being particularly basal species such as ''
Zuolong salleei ''Zuolong'' (Zuo's dragon) is a genus of coelurosaur dinosaur which existed in what is now Wucaiwan, Xinjiang Autonomous Region of China during the Late Jurassic period (lower Oxfordian stage). It was found in the Shishugou Formation, Xinjia ...
or Sciurumimus albersdoerferi''. Within Tyrannoraptora exists a slightly less inclusive
clade A clade (), also known as a monophyletic group or natural group, is a group of organisms that are monophyletic – that is, composed of a common ancestor and all its lineal descendants – on a phylogenetic tree. Rather than the English ter ...
named Neocoelurosauria erected by Hendrickx, Mateus, Araújo and Choiniere (2019), defining it as "the clade Compsognathidae + Maniraptoriformes", which can be more or less inclusive than Maniraptoromorpha depending on the topology. The following family tree illustrates a synthesis of the relationships of the major coelurosaurian groups based on various studies conducted in the 2010s.Hendrickx, C., Hartman, S.A., & Mateus, O. (2015). An Overview of Non- Avian Theropod Discoveries and Classification. ''PalArch’s Journal of Vertebrate Palaeontology'', 12(1): 1-73.


"Coelurosaurus"

"Coelurosaurus" is an
informal Formal, formality, informal or informality imply the complying with, or not complying with, some set of requirements (forms, in Ancient Greek). They may refer to: Dress code and events * Formal wear, attire for formal events * Semi-formal attir ...
generic Generic or generics may refer to: In business * Generic term, a common name used for a range or class of similar things not protected by trademark * Generic brand, a brand for a product that does not have an associated brand or trademark, other ...
name, attributed to
Friedrich von Huene Friedrich von Huene, born Friedrich Richard von Hoinigen, (March 22, 1875 – April 4, 1969) was a German paleontologist who renamed more dinosaurs in the early 20th century than anyone else in Europe. He also made key contributions about v ...
, 1929, that is sometimes seen in lists of dinosaurs. It probably arose as a
typographical error A typographical error (often shortened to typo), also called a misprint, is a mistake (such as a spelling mistake) made in the typing of printed (or electronic) material. Historically, this referred to mistakes in manual type-setting (typography) ...
; von Huene intended to assign indeterminate remains to Coelurosauria '' incertae sedis'', but at some point in the process of publication a revision to the text made it appear that he was creating a new generic name "Coelurosaurus" (as described by George Olshevsky in a 1999 post to the Dinosaur Mailing List). The name is undescribed and has not been used seriously, although it has appeared in works of fiction.


See also

* Feathered dinosaurs * Origin of birds * List of fossil birds


References


References

* * * Mayr, G., B. Pohl & D.S. Peters (2005). "A well-preserved ''Archaeopteryx'' specimen with theropod features". ''Science'', 310(5753): 1483–1486. * (on "Coelurosaurus") * * Senter, P. (2007). "A new look at the phylogeny of Coelurosauria (Dinosauria: Theropoda)." ''Journal of Systematic Palaeontology'', (). * Zanno, L.E., Gillette, D.D., Albright, L.B., and Titus, A.L. (2009). "A new North American therizinosaurid and the role of herbivory in 'predatory' dinosaur evolution." ''Proceedings of the Royal Society B'', Published online before print July 15, 2009, .
First Dinosaur Tail Found Preserved in Amber
''National Geographic'', December 8, 2016.


External links


Paleobiology Database: Coelurosauria





Tree of Life Web: Coelurosauria
{{Authority control Late Jurassic dinosaurs Cretaceous dinosaurs Cenozoic dinosaurs Extant Middle Jurassic first appearances Fossil taxa described in 1914 Taxa named by Friedrich von Huene