This is an accepted version of this page
114-461: Noasauridae is an extinct family of theropod dinosaurs belonging to the group Ceratosauria . They were closely related to the short-armed abelisaurids , although most noasaurids had much more traditional body types generally similar to other theropods. Their heads, on the other hand, had unusual adaptations depending on the subfamily. 'Traditional' noasaurids, sometimes grouped in the subfamily Noasaurinae, had sharp teeth which splayed outwards from
228-695: A Compsognathus longipes fossil was found with a lizard in its stomach, and a Velociraptor mongoliensis specimen was found locked in combat with a Protoceratops andrewsi (a type of ornithischian dinosaur). The first confirmed non-carnivorous fossil theropods found were the therizinosaurs , originally known as "segnosaurs". First thought to be prosauropods , these enigmatic dinosaurs were later proven to be highly specialized, herbivorous theropods. Therizinosaurs possessed large abdomens for processing plant food, and small heads with beaks and leaf-shaped teeth. Further study of maniraptoran theropods and their relationships showed that therizinosaurs were not
342-460: A scapulocoracoid . While the presence of a scapulocoracoid is by no means unique to this family, noasaurids do have particularly large and wide scapulocoracoids, with a tall and semicircular coracoid region. The hooked rear edge of the coracoid region is also offset from the glenoid (shoulder socket) by a large U-shaped notch. The humerus (upper arm bone) was thin and straight, with a low and somewhat rounded humeral head (the portion which attached to
456-461: A 1999 paper by Paul Sereno suggests that theropods are characterized by traits such as an ectopterygoid fossa (a depression around the ectopterygoid bone), an intramandibular joint located within the lower jaw, and extreme internal cavitation within the bones. However, since taxa like Herrerasaurus may not be theropods, these traits may have been more widely distributed among early saurischians rather than being unique to theropods. Instead, taxa with
570-490: A bird-like arrangement of the pectoral bones, where the angled shoulder girdle (coracoids) come in contact with the breastbone (sternum). According to Paul, ornithomimosaurs are the most basal members of this group. In 2010, Paul used Avepectora for a smaller clade, excluding ornithomimosaurs, compsognathids and alvarezsauroids. Within Coelurosauria exists a slightly less inclusive clade named Tyrannoraptora . This clade
684-520: A carnivorous or omnivorous diet. The largest known noasaurid, Elaphrosaurus , is the namesake of Elaphrosaurinae. Members of this genus could grow up to 20 feet (6.1 meters) long, although they were significantly lighter than similarly sized carnivorous contemporaries such as Ceratosaurus . Rauhut & Carrano (2016) listed several features which could be used to diagnose Elaphrosaurinae. Elaphrosaurine cervical vertebrae are amphicoelous, meaning that both their front and rear faces are concave, particularly
798-467: A common origin with avemetatarsalians . 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
912-474: 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." Studies show that theropods had very sensitive snouts. It
1026-581: A downturned lower jaw. The most complete and well-known example of these kinds of noasaurids was Masiakasaurus knopfleri from Madagascar. Another group, Elaphrosaurinae, has also been placed within Noasauridae by some studies. Elaphrosaurines developed toothless jaws and herbivorous diets, at least as adults. The most complete and well known elaphrosaurine was Limusaurus inextricabilis . At least some noasaurids had pneumatised cervical vertebrae. Some are considered to have had cursorial habits. Noasauridae
1140-467: A femur approximately the same length of the ilium. The connection between the ilium and the pubis (forward-projecting rod-like lower bone of the hip) is also more simple than in other ceratosaurians. While other ceratosaurians have a peg-and-socket connection between the two bones, elaphrosaurines simply have a flat contact between the two. In 2020 a middle cervical vertebra from the lower Albian Eumeralla Formation of Cape Otway , Victoria, Australia
1254-470: A few species of abelisaurids) also have reduced fourth trochanters. In addition, the two subfamilies have a metatarsal II (the foot bone connected to the innermost major toe) which was flattened from the side. Further reductions to this metatarsal were present in noasaurines (particularly Velocisaurus ). In these genera as well as Deltadromeus , metatarsal IV (which connected to the outermost major toe) also became reduced in some respects. In all noasaurids,
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#17330847097591368-416: A group including the relatively derived theropod subgroups Ceratosauria and Tetanurae , and excluding coelophysoids . However, most later researchers have used it to denote a broader group. Neotheropoda was first defined as a clade by Paul Sereno in 1998 as Coelophysis plus modern birds , which includes almost all theropods except the most primitive species. Dilophosauridae was formerly considered
1482-452: A higher probability of being within the Theropoda may share more specific traits, such as a prominent promaxillary fenestra, cervical vertebrae with pleurocoels in the anterior part of the centrum leading to a more pneumatic neck, five or more sacral vertebrae, enlargement of the carpal bone, and a distally concave portion of the tibia, among a few other traits found throughout the skeleton. Like
1596-416: A relationships between tooth size and skull length and also a comparison of the degree of wear of the teeth of non-avian theropods and modern lepidosaurs , it is concluded that theropods had lips that protected their teeth from the outside. Visually, the snouts of such theropods as Daspletosaurus had more similarities with lizards than crocodilians, which lack lips. Tyrannosaurus was for many decades
1710-428: A result of growth or seasonal changes, which can be used to approximate age at the time of death. However, the amount of rings in a skeleton can vary from bone to bone, and old rings can also be lost at advanced age, so scientists need to properly control these two possibly confounding variables. Body mass is harder to determine as bone mass only represents a small proportion of the total body mass of animals. One method
1824-541: A result the appearance and biology of the average noasaurine must be inferred from the most complete member of the group, Masiakasaurus . Rauhut & Carrano (2016) define Noasaurinae as "all noasaurids more closely related to Noasaurus than to Elaphrosaurus , Abelisaurus , Ceratosaurus , or Allosaurus " . Masiakasaurus (and presumably other noasaurines) had a downturned lower jaw with long teeth splaying forwards. These teeth were spoon-shaped with sharply pointed tips and serrations along their outer edge. The rest of
1938-410: A shift in the use of the forearm, with greater flexibility at the shoulder allowing the arm to be raised towards the horizontal plane, and to even greater degrees in flying birds. However, in coelurosaurs, such as ornithomimosaurs and especially dromaeosaurids, the hand itself had lost most flexibility, with highly inflexible fingers. Dromaeosaurids and other maniraptorans also showed increased mobility at
2052-478: A side-branch of more advanced theropods, they may have been ancestral to all other theropods (which would make them a paraphyletic group). Neotheropoda (meaning "new theropods") is a clade that includes coelophysoids and more advanced theropod dinosaurs , and is the only group of theropods that survived the Triassic–Jurassic extinction event . Neotheropoda was named by R.T. Bakker in 1986 as
2166-657: A single unambiguous trait used to diagnose noasaurines to the exception of other noasaurids. That trait is the fact that their metatarsal II has a diminished proximal (near) end. One noasaurine, Velocisaurus , took this trait even further, with both its metatarsal II and IV reduced to very thin rod-like bones along their entire length. It is not entirely certain if elaphrosaurines are legitimate examples of noasaurids. Both Limusaurus and Elaphrosaurus have been considered basal ceratosaurians by many studies, with most of these studies considering them even more primitive than Ceratosaurus . The most well-known elaphrosaurines lived during
2280-425: A single unit with little flexibility. In theropods and prosauropods, the only way for the palm to face the ground would have been by lateral splaying of the entire forelimb, as in a bird raising its wing. In carnosaurs like Acrocanthosaurus , the hand itself retained a relatively high degree of flexibility, with mobile fingers. This was also true of more basal theropods, such as herrerasaurs . Coelurosaurs showed
2394-525: A small clade within Neotheropoda, but was later considered to be paraphyletic . By the Early Jurassic , all non-averostran neotheropods had gone extinct. Averostra (or "bird snouts") is a clade within Neotheropoda that includes most theropod dinosaurs , namely Ceratosauria and Tetanurae . It represents the only group of post-Early Jurassic theropods. One important diagnostic feature of Averostra
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#17330847097592508-534: A study by paleontologist Thomas Holtz found a close relationship between the Ornithomimosauria and Troodontidae , and named this group Bullatosauria . Holtz rejected this hypothesis in 1999, and most paleontologists now consider troodontids to be much more closely related to either birds or Dromaeosauridae than they are to ornithomimosaurs, causing the Bullatosauria to be abandoned. The name referred to
2622-406: A wide variety of tasks (see below). In modern birds, the body is typically held in a somewhat upright position, with the upper leg (femur) held parallel to the spine and with the forward force of locomotion generated at the knee. Scientists are not certain how far back in the theropod family tree this type of posture and locomotion extends. Non-avian theropods were first recognized as bipedal during
2736-558: A within Noasauridae. In 2016, a redescription of Elaphrosaurus by Oliver Rauhut and Matthew Carrano argued against earlier hypotheses that elaphrosaurines were basal ceratosaurs, instead placing them alongside noasaurines within a monophyletic Noasauridae. This study formally defined Elaphrosaurinae as "all noasaurids more closely related to Elaphrosaurus than to Noasaurus , Abelisaurus , Ceratosaurus , or Allosaurus". Generally speaking, elaphrosaurines were lightly built theropods, with small skulls and long necks and legs. If Limusaurus
2850-499: Is Neocoelurosauria , erected by Hendrickx, Mateus, Araújo and Choiniere (2019), They define it as "the clade Compsognathidae + Maniraptoriformes", which can be more or less inclusive than Maniraptoromorpha depending on the topology. The last, and most exclusive of these proposed subclades is Maniraptoriformes . Maniraptoriformes is a clade which may have been united by the presence of pennaceous feathers and wings. This clade contains ornithomimosaurs and maniraptorans . The group
2964-575: Is a particularly controversial genus, as it shares many features with noasaurids but is also very similar to Gualicho , which has been classified as a close relative of the enigmatic (but generally considered non- ceratosaurian ) megaraptorans . A 2017 study describing ontogenetic changes in Limusaurus and the effect of juvenile taxa on phylogenetic analyses provided various phylogenetic trees which varied based on which Limusaurus specimens were used. The structure of Noasauridae changed greatly depending on
3078-468: Is also believed to have also been different among different families. The spinosaurids could have used their powerful forelimbs to hold fish. Some small maniraptorans such as scansoriopterygids are believed to have used their forelimbs to climb in trees . The wings of modern birds are used primarily for flight, though they are adapted for other purposes in certain groups. For example, aquatic birds such as penguins use their wings as flippers. Contrary to
3192-482: Is an extant 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 carnivorous , although a number of theropod groups evolved to become herbivores and omnivores . Theropods first appeared during the Carnian age of the late Triassic period 231.4 million years ago ( Ma ) and included
3306-505: Is any indication, adult elaphrosaurines were completely toothless, and their mouths were probably edged with a horny beak. It is likely that Limusaurus and other elaphrosaurines were primarily herbivorous as adults, due to mature Limusaurus specimens preserving gastroliths and chemical signatures resembling those of herbivorous dinosaurs. However, juvenile Limusaurus specimens retained teeth and lacked these signs of herbivory, meaning that young elaphrosaurines may have been more capable of
3420-416: Is defined as all theropods closer to Noasaurus than to Abelis aurus . Noasauridae was a very diverse group, with the two most complete members, Masiakasaurus and Limusaurus , showing unusual features very different from each other. Masiakasaurus had an unusually downturned jaw, with long and sharply pointed spoon-shaped teeth. Some of these teeth were nearly horizontal in orientation. Limusaurus , on
3534-467: Is known as the extant-scaling (ES) approach. A second method, known as the volumetric-density (VD) approach, uses full-scale models of skeletons to make inferences about potential mass. The ES approach is better for wide-range studies including many specimens and doesn't require as much of a complete skeleton as the VD approach, but the VD approach allows scientists to better answer more physiological questions about
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3648-512: Is suggested they might have been used for temperature detection, feeding behavior, and wave detection. Shortened forelimbs in relation to hind legs was a common trait among theropods, most notably in the abelisaurids (such as Carnotaurus ) and the tyrannosaurids (such as Tyrannosaurus ). This trait was, however, not universal: spinosaurids had well developed forelimbs, as did many coelurosaurs. The relatively robust forelimbs of one genus, Xuanhanosaurus , led D. Zhiming to suggest that
3762-417: Is that their cervical ribs are completely fused to the centrum (main body) of their corresponding vertebrae. Elaphrosaurines also have several diagnostic hip features. The hip is quite small compared to their long legs. The femur (thigh bone) is more than 1.3 times the length of the ilium (upper plate-like bone of the hip) in members of this subfamily, while most other ceratosaurians have shorter legs and
3876-659: 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 , tyrannosaurs , ornithomimosaurs , and maniraptorans ; Maniraptora includes birds , the only known dinosaur group alive today. Most feathered dinosaurs discovered so far have been coelurosaurs. Philip J. Currie 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
3990-565: Is the absence of the fifth metacarpal. Other saurischians retained this bone, albeit in a significantly reduced form. The somewhat more advanced ceratosaurs (including Ceratosaurus and Carnotaurus ) appeared during the Early Jurassic and continued through to the Late Jurassic in Laurasia . They competed alongside their more anatomically advanced tetanuran relatives and—in the form of
4104-408: Is to measure the circumference of the femur, which in non-avian theropod dinosaurs has been shown to be a relatively proportional to quadrupedal mammals, and use this measurement as a function of body weight, as the proportions of long bones like the femur grow proportionately with body mass. The method of using extant animal bone proportion to body mass ratios to make predictions about extinct animals
4218-429: 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
4332-439: Is used to signify groups with no living members. The following family tree illustrates a synthesis of the relationships of the major theropod groups based on various studies conducted in the 2010s. † Herrerasauridae [REDACTED] † Eoraptor † Eodromaeus † Daemonosaurus Coelurosauria Coelurosauria ( / s ɪ ˌ lj ʊər ə ˈ s ɔːr i . ə / ; from Greek , meaning "hollow-tailed lizards")
4446-592: The Allosauroidea (the diverse carcharodontosaurs ) and the Coelurosauria (a very large and diverse dinosaur group including the birds). Thus, during the late Jurassic, there were no fewer than four distinct lineages of theropods—ceratosaurs, megalosaurs, allosaurs, and coelurosaurs—preying on the abundance of small and large herbivorous dinosaurs. All four groups survived into the Cretaceous, and three of those—the ceratosaurs, coelurosaurs, and allosaurs—survived to end of
4560-647: The Coelophysoidea . The coelophysoids were a group of widely distributed, lightly built and potentially gregarious animals. They included small hunters like Coelophysis and Camposaurus . These successful animals continued from the Late Carnian (early Late Triassic) through to the Toarcian (late Early Jurassic ). Although in the early cladistic classifications they were included under the Ceratosauria and considered
4674-608: The Jurassic period, much older than the Late Cretaceous period noasaurines. Nevertheless, the existence of Eoabelisaurus shows that abelisauroids had evolved by the Jurassic period, and Cretaceous elaphrosaurines such as Huinculsaurus have been discovered. It would make sense for Noasauridae (the sister taxa to Abelisauridae) to have evolved during the Jurassic, meaning that the early appearance of elaphrosaurines would not preclude
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4788-648: The Morrison Formation 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 , a superb range of coelurosaurian fossils (including avians) are known from
4902-648: 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 , are best known from the late Cretaceous. A majority of coelurosaur groups became extinct in the Cretaceous–Paleogene extinction event , including
5016-584: The abelisaur lineage—lasted to the end of the Cretaceous in Gondwana . The Tetanurae are more specialised again than the ceratosaurs. They are subdivided into the basal Megalosauroidea (alternately Spinosauroidea ) and the more derived Avetheropoda . Megalosauridae were primarily Middle Jurassic to Early Cretaceous predators, and their spinosaurid relatives' remains are mostly from Early and Middle Cretaceous rocks. Avetheropoda, as their name indicates, were more closely related to birds and are again divided into
5130-407: The bee hummingbird ( Mellisuga helenae ) is smallest at 1.9 g and 5.5 cm (2.2 in) long. Recent theories propose that theropod body size shrank continuously over a period of 50 million years, from an average of 163 kilograms (359 lb) down to 0.8 kilograms (1.8 lb), eventually evolving into over 11,000 species of modern birds . This was based on evidence that theropods were
5244-475: The clade Tetanurae for one branch of a basic theropod split with another group, the Ceratosauria. As more information about the link between dinosaurs and birds came to light, the more bird-like theropods were grouped in the clade Maniraptora (also named by Gauthier in 1986 ). These new developments also came with a recognition among most scientists that birds arose directly from maniraptoran theropods and, on
5358-742: The coelurosaurs , feathers may have been confined to the young, smaller species, or limited parts of the animal. Many larger theropods had skin covered in small, bumpy scales. In some species, these were interspersed with larger scales with bony cores, or osteoderms . This type of skin is best known in the ceratosaur Carnotaurus , which has been preserved with extensive skin impressions. The coelurosaur lineages most distant from birds had feathers that were relatively short and composed of simple, possibly branching filaments. Simple filaments are also seen in therizinosaurs, which also possessed large, stiffened "quill"-like feathers. More fully feathered theropods, such as dromaeosaurids , usually retain scales only on
5472-524: The cranium and forelimb, with injuries occurring in about equal frequency at each site. Most pathologies preserved in theropod fossils are the remains of injuries like fractures, pits, and punctures, often likely originating with bites. Some theropod paleopathologies seem to be evidence of infections , which tended to be confined only to small regions of the animal's body. Evidence for congenital malformities have also been found in theropod remains. Such discoveries can provide information useful for understanding
5586-630: The furcula (wishbone), pneumatized bones, brooding of the eggs , and (in coelurosaurs, at least) feathers . O. C. Marsh coined the name Theropoda (meaning "beast feet") in 1881. Marsh initially named Theropoda as a suborder to include the family Allosauridae , but later expanded its scope, re-ranking it as an order to include a wide array of "carnivorous" dinosaur families, including Megalosauridae , Compsognathidae , Ornithomimidae , Plateosauridae and Anchisauridae (now known to be herbivorous sauropodomorphs ) and Hallopodidae (subsequently revealed as relatives of crocodilians). Due to
5700-458: The proceratosaurid tyrannosauroids Proceratosaurus and Kileskus from the late Middle Jurassic. Many nearly complete fossil coelurosaurians are known from the Late Jurassic . Archaeopteryx (incl. Wellnhoferia ) is known from Bavaria at 155-150 Ma. Ornitholestes , the troodontid Hesperornithoides , Coelurus fragilis and Tanycolagreus topwilsoni are all known from
5814-455: The spinosaurids ) appear to have specialized in catching fish. Diet is largely deduced by the tooth morphology , tooth marks on bones of the prey, and gut contents. Some theropods, such as Baryonyx , Lourinhanosaurus , ornithomimosaurs, and birds, are known to use gastroliths , or gizzard-stones. The majority of theropod teeth are blade-like, with serration on the edges, called ziphodont. Others are pachydont or folidont depending on
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#17330847097595928-469: The tyrannosaurids , 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 . 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. In 1994,
6042-505: 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
6156-480: The 19th century, before their relationship to birds was widely accepted. During this period, theropods such as carnosaurs and tyrannosaurids were thought to have walked with vertical femurs and spines in an upright, nearly erect posture, using their long, muscular tails as additional support in a kangaroo-like tripodal stance. Beginning in the 1970s, biomechanical studies of extinct giant theropods cast doubt on this interpretation. Studies of limb bone articulation and
6270-461: The Early Cretaceous. A few palaeontologists, such as Gregory S. Paul , have suggested that some or all of these advanced theropods were actually descended from flying dinosaurs or proto-birds like Archaeopteryx that lost the ability to fly and returned to a terrestrial habitat. The evolution of birds from other theropod dinosaurs has also been reported, with some of the linking features being
6384-667: The Order Saurischia into two suborders, Theropoda and Sauropoda. This basic division has survived into modern palaeontology, with the exception of, again, the Prosauropoda, which Romer included as an infraorder of theropods. Romer also maintained a division between Coelurosauria and Carnosauria (which he also ranked as infraorders). This dichotomy was upset by the discovery of Deinonychus and Deinocheirus in 1969, neither of which could be classified easily as "carnosaurs" or "coelurosaurs". In light of these and other discoveries, by
6498-461: The Tetanurae and Ceratosauria. While some used to consider coelophysoids and ceratosaurs to be within the same group due to features such as a fused hip, later studies showed that it is more likely that these were features ancestral to neotheropods and were lost in basal tetanurans. Averostrans and their close relatives are united via the complete loss of any digit V remnants, fewer teeth in the maxilla,
6612-555: The Tyrannosauroidea, Ornithomimosauria , Oviraptorosauria , Deinonychosauria , Enantiornithes , 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 definitions, birds are considered
6726-510: The abandonment of ranks in cladistic classification, with the re-evaluation of birds as a subset of theropod dinosaurs that survived the Mesozoic extinctions and lived into the present. The following is a simplified classification of theropod groups based on their evolutionary relationships, and organized based on the list of Mesozoic dinosaur species provided by Holtz. A more detailed version can be found at dinosaur classification . The dagger (†)
6840-506: The age of the Limusaurus specimens, although Genusaurus and Deltadromeus were resolved as noasaurids in each diagnosis. [REDACTED] [REDACTED] [REDACTED] [REDACTED] [REDACTED] Theropod This is an accepted version of this page Theropoda ( / θ ɪəˈr ɒ p ə d ə / ; from ancient Greek θηρίο- ποδός [ θηρίον , ( therion ) "wild beast"; πούς , ποδός ( pous, podos ) "foot"]) whose members are known as theropods ,
6954-546: The animal might have been quadrupedal. However, this is no longer thought to be likely. The hands are also very different among the different groups. The most common form among non-avian theropods is an appendage consisting of three fingers; the digits I, II and III (or possibly II, III and IV ), with sharp claws. Some basal theropods, like most Ceratosaurians , had four digits, and also a reduced metacarpal V (e.g. Dilophosaurus ). The majority of tetanurans had three, but some had even fewer. The forelimbs' scope of use
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#17330847097597068-459: The animal, such as locomotion and center of gravity. The current consensus is that non-avian theropods didn't exhibit a group wide growth rate, but instead had varied rates depending on their size. However, all non-avian theropods had faster growth rates than extant reptiles, even when modern reptiles are scaled up to the large size of some non-avian theropods. As body mass increases, the relative growth rate also increases. This trend may be due to
7182-484: The avian theropods (birds). However, discoveries in the late 20th and early 21st centuries showed that a variety of diets existed even in more basal lineages. All early finds of theropod fossils showed them to be primarily carnivorous . Fossilized specimens of early theropods known to scientists in the 19th and early 20th centuries all possessed sharp teeth with serrated edges for cutting flesh, and some specimens even showed direct evidence of predatory behavior. For example,
7296-729: The cervicals of most of the neck, although they diminish near the neck. Epipophyses are bony projections located above the postzygapophyses (joints on the rear edge of a vertebra connecting to the front edge of the following vertebra). Elaphrosaurines, on the other hand, have cervical epipophyses which are much more diminished or even absent in the case of Elaphrosaurus . Many noasaurids are only known from vertebrae, including both valid ( Laevisuchus , Spinostropheus ) and dubious ( Composuchus , Jubbulpuria , Ornithomimoides , Coeluroides ) genera. Noasaurines are Late Cretaceous noasaurids known exclusively from southern continents and islands such as South America , Madagascar , and India (which
7410-408: The composition of Noasauridae has been difficult to resolve. An analysis conducted by Tortosa et al. ( 2013) recovered Dahalokely as a basal noasaurid. However, another analysis later that year found it to be a basal carnotaurine instead. Similarly, the genus Genusaurus has been found to be a noasaurid by some older studies, but other studies have classified it as an abelisaurid. Deltadromeus
7524-499: The different parts of theropod anatomy. The most common sites of preserved injury and disease in theropod dinosaurs are the ribs and tail vertebrae . Despite being abundant in ribs and vertebrae, injuries seem to be "absent... or very rare" on the bodies' primary weight supporting bones like the sacrum , femur , and tibia . The lack of preserved injuries in these bones suggests that they were selected by evolution for resistance to breakage. The least common sites of preserved injury are
7638-421: The early sauropodomorphs, the second digit in a theropod's hand is enlarged. Theropods also have a very well developed ball and socket joint near their neck and head. Most theropods belong to the clade Neotheropoda, characterized by the reduction of several foot bones, thus leaving three toed footprints on the ground when they walk (tridactyl feet). Digit V was reduced to a remnant early in theropod evolution and
7752-414: The elaphrosaurines within Noasauridae. If these groups did not belong to Noasauridae as the study claims, then these similarities are examples of convergent evolution . Among the most prominent traits relate to the shoulder region. In this family, the long, upward-stretching scapula (shoulder blade) merges with the smaller and more compact coracoid (shoulder girdle), forming a fused shoulder bone known as
7866-553: The evolutionary history of the processes of biological development. Unusual fusions in cranial elements or asymmetries in the same are probably evidence that one is examining the fossils of an extremely old individual rather than a diseased one. The trackway of a swimming theropod, the first in China of the ichnogenus named Characichnos , was discovered at the Feitianshan Formation in Sichuan. These new swim tracks support
7980-580: The extent that abelisaurids acquired. Noasaurids were also nimble and lightly built, with feet showing adaptations for running such as a long central foot bone (metatarsal III). Noasaurids varied in size, from the small Velocisaurus which was under 5 feet (1.5 meters) long, to much larger genera such as Elaphrosaurus and Deltadromeus , which were more than 20 feet (6.1 meters) in length. A collection of features which characterize noasaurids in particular has been compiled by Rauhut & Carrano (2016), who included controversial taxa such as Deltadromeus and
8094-572: 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 ornithischian dinosaurs (like Tianyulong and Kulindadromeus ), and in pterosaurs . Though it
8208-413: The feet. Some species may have mixed feathers elsewhere on the body as well. Scansoriopteryx preserved scales near the underside of the tail, and Juravenator may have been predominantly scaly with some simple filaments interspersed. On the other hand, some theropods were completely covered with feathers, such as the troodontid Anchiornis , which even had feathers on the feet and toes. Based on
8322-422: The femur (thigh bone) of a noasaurid had a ridge along the inner rear surface, known as a fourth trochanter . However, in noasaurines and elaphrosaurines (but not necessarily other genera such as Deltadromeus ), this fourth trochanter was much smaller and lower than the enlarged crest-like structure present in the majority of basal theropods; only a few other groups of theropods ( coelophysoids , coelurosaurs , and
8436-470: The first known dromaeosaurid ( Dromaeosaurus albertensis ) in 1922, W. D. Matthew and Barnum Brown became the first paleontologists to exclude prosauropods from the carnivorous dinosaurs, and attempted to revive the name "Goniopoda" for that group, but other scientists did not accept either of these suggestions. In 1956, "Theropoda" came back into use—as a taxon containing the carnivorous dinosaurs and their descendants—when Alfred Romer re-classified
8550-460: The front face which is quite strongly concave. While strongly concave front faces are common among many archosaurs, they are quite rare in all but the most basal theropods. Carnosaurs , megalosauroids , coelurosaurs, and most other ceratosaurians (including noasaurines) all have vertebrae which have front faces ranging from very weakly concave to flat (platycoelous) or convex (opisthocoelous). Another notable feature of elaphrosaurine cervical vertebrae
8664-526: The heaviest theropods known to science. It is still not clear why these animals grew so heavy and bulky compared to the land predators that came before and after them. The largest extant theropod is the common ostrich , up to 2.74 m (9 ft) tall and weighing between 90 and 130 kg (200 - 290 lb). The smallest non-avian theropod known from adult specimens is the troodontid Anchiornis huxleyi , at 110 grams in weight and 34 centimeters (1 ft) in length. When modern birds are included,
8778-608: The hypothesis that theropods were adapted to swimming and capable of traversing moderately deep water. Dinosaur swim tracks are considered to be rare trace fossils, and are among a class of vertebrate swim tracks that also include those of pterosaurs and crocodylomorphs . The study described and analyzed four complete natural molds of theropod foot prints that are now stored at the Huaxia Dinosaur Tracks Research and Development Center (HDT). These dinosaur footprints were in fact claw marks, which suggest that this theropod
8892-426: The inflated (bulbous) sphenoid both groups shared. Holtz defined the group as the clade containing the most recent common ancestor of Troodon and Ornithomimus and all its descendants. The concept is now considered redundant, and the clade Bullatosauria is now viewed as synonymous with Maniraptoriformes. In 2002, Gregory S. Paul named an apomorphy-based clade Avepectora , defined to include all theropods with
9006-422: The knee was normally strongly flexed in all theropods while walking, even giants like the tyrannosaurids. It is likely that a wide range of body postures, stances, and gaits existed in the many extinct theropod groups. Although rare, complete casts of theropod endocrania are known from fossils. Theropod endocrania can also be reconstructed from preserved brain cases without damaging valuable specimens by using
9120-490: The largest ( Tyrannosaurus ) and smallest ( Microraptor , Parvicursor ) carnivorous dinosaurs ever discovered. Characteristics that distinguish coelurosaurs include: Fossil evidence shows that the skin of even the most primitive coelurosaurs was covered primarily in feathers . 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
9234-544: The largest known theropod and best known to the general public. Since its discovery, however, a number of other giant carnivorous dinosaurs have been described, including Spinosaurus , Carcharodontosaurus , and Giganotosaurus . The original Spinosaurus specimens (as well as newer fossils described in 2006) support the idea that Spinosaurus was probably 3 meters longer than Tyrannosaurus , though Tyrannosaurus might have been more massive than Spinosaurus . Specimens such as Sue and Scotty are both estimated to be
9348-464: The largest living land animal today, the African elephant , which is characterized by a rapid period of growth until maturity, subsequently followed by slowing growth in adulthood. As a hugely diverse group of animals, the posture adopted by theropods likely varied considerably between various lineages through time. All known theropods are bipedal , with the forelimbs reduced in length and specialized for
9462-457: The late 1970s Rinchen Barsbold had created a new series of theropod infraorders: Coelurosauria, Deinonychosauria , Oviraptorosauria , Carnosauria, Ornithomimosauria, and Deinocheirosauria . With the advent of cladistics and phylogenetic nomenclature in the 1980s, and their development in the 1990s and 2000s, a clearer picture of theropod relationships began to emerge. Jacques Gauthier named several major theropod groups in 1986, including
9576-453: The majority of large terrestrial carnivores from the Early Jurassic until at least the close of the Cretaceous , about 66 Ma. In the Jurassic , birds evolved from small specialized coelurosaurian theropods, and are today represented by about 11,000 living species. Various synapomorphies for Theropoda have been proposed based on which taxa are included in the group. For example,
9690-531: The mid caudals (vertebrae in the middle of the tail) had very low neural spines. The cervical (neck) vertebrae, on the other hand, were quite varied within this family. In noasaurines and a few other genera (such as Laevisuchus ), the neural spines of vertebrae at the front of the neck were positioned towards the front part of their respective vertebrae. This is quite unusual compared to other theropods, which have neural spines roughly midway down their vertebrae. These genera also have long and spine-like epipophyses on
9804-404: The movement of the tooth row further down the maxilla and a lacrimal fenestra. Averostrans also share features in their hips and teeth. Theropods exhibit a wide range of diets, from insectivores to herbivores and carnivores. Strict carnivory has always been considered the ancestral diet for theropods as a group, and a wider variety of diets was historically considered a characteristic exclusive to
9918-660: The need to reach the size required for reproductive maturity . For example, one of the smallest known theropods was Microraptor zhaoianus , which had a body mass of 200 grams, grew at a rate of approximately 0.33 grams per day. A comparable reptile of the same size grows at half of this rate. The growth rates of medium-sized non-avian theropods (100–1000 kg) approximated those of precocial birds, which are much slower than altricial birds. Large theropods (1500–3500 kg) grew even faster, similar to rates displayed by eutherian mammals. The largest non-avian theropods, like Tyrannosaurus rex had similar growth dynamics to
10032-491: The oldest known bird, Archaeopteryx ), the bird-like troodontids and oviraptorosaurs, the ornithomimosaurs (or "ostrich Dinosaurs"), the strange giant-clawed herbivorous therizinosaurs, and the avialans, which include modern birds and is the only dinosaur lineage to survive the Cretaceous–Paleogene extinction event . While the roots of these various groups are found in the Middle Jurassic, they only became abundant during
10146-492: The only dinosaurs to get continuously smaller, and that their skeletons changed four times as fast as those of other dinosaur species. In order to estimate the growth rates of theropods, scientists need to calculate both age and body mass of a dinosaur. Both of these measures can only be calculated through fossilized bone and tissue , so regression analysis and extant animal growth rates as proxies are used to make predictions. Fossilized bones exhibit growth rings that appear as
10260-407: The only early members of this group to abandon carnivory. Several other lineages of early maniraptorans show adaptations for an omnivorous diet, including seed-eating (some troodontids ) and insect-eating (many avialans and alvarezsaurs ). Oviraptorosaurs , ornithomimosaurs and advanced troodontids were likely omnivorous as well, and some early theropods (such as Masiakasaurus knopfleri and
10374-427: The only exceptions being particularly basal species such as Zuolong salleei or Sciurumimus albersdoerferi . Several recently-named clades have been proposed to define the structure of Coelurosauria crownward of basal groups such as tyrannosauroids and compsognathids. Maniraptoromorpha , defined by Andrea Cau in 2018, includes all coelurosaurians more closely related to birds than to tyrannosauroids. Cau stated that
10488-419: 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. The phylogeny and taxonomy of Coelurosauria has been subject to intensive research and revision. For many years, Coelurosauria was a 'dumping ground' for all small theropods. In
10602-622: The other hand, was completely toothless as an adult and likely possessed a horny beak. This large disparity means that it is difficult to find any skull features shared by members of Noasauridae as a whole. Noasaurids had longer arms than their relatives the abelisaurids, whose arms were tiny and diminished. Although by no means as large or specialized as the arms of advanced bird-like theropods, noasaurid arms were nevertheless capable of movement and use, possibly even for hunting in large-clawed genera such as Noasaurus . Some genera such as Limusaurus did have somewhat reduced arms and hands, but far from
10716-418: The palms faced the ground or backwards towards the legs. In humans, pronation is achieved by motion of the radius relative to the ulna (the two bones of the forearm). In saurischian dinosaurs, however, the end of the radius near the elbow was actually locked into a groove of the ulna, preventing any movement. Movement at the wrist was also limited in many species, forcing the entire forearm and hand to move as
10830-400: The past considered the herrerasaurians to be members of Theropoda, while other theorized the group to be basal saurischians, and may even have evolved prior to the saurischian-ornithischian split. Cladistic analysis following the discovery of Tawa , another Triassic dinosaur, suggests the herrerasaurs likely were early theropods. The earliest and most primitive unambiguous theropods are
10944-620: The past, Coelurosauria was used to refer to all small theropods, but this classification has since been amended. 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 ), herbivorous ( Therizinosauridae ) and carnivorous ( Tyrannosauroidea and Dromaeosauridae ). The group includes some of
11058-531: The period, where they were geographically separate, the ceratosaurs and allosaurs in Gondwana, and the coelurosaurs in Laurasia. Of all the theropod groups, the coelurosaurs were by far the most diverse. Some coelurosaur groups that flourished during the Cretaceous were the tyrannosaurids (including Tyrannosaurus ), the dromaeosaurids (including Velociraptor and Deinonychus , which are remarkably similar in form to
11172-439: 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." A few fossil traces tentatively associated with the Coelurosauria date as far back as the late Triassic . What has been found between then and the earliest Middle Jurassic is fragmentary. The oldest known unambiguous members of Coelurosauria are
11286-439: The relative absence of trackway evidence for tail dragging suggested that, when walking, the giant, long-tailed theropods would have adopted a more horizontal posture with the tail held parallel to the ground. However, the orientation of the legs in these species while walking remains controversial. Some studies support a traditional vertically oriented femur, at least in the largest long-tailed theropods, while others suggest that
11400-468: The scope of Marsh's Order Theropoda, it came to replace a previous taxonomic group that Marsh's rival E. D. Cope had created in 1866 for the carnivorous dinosaurs: Goniopoda ("angled feet"). By the early 20th century, some palaeontologists, such as Friedrich von Huene , no longer considered carnivorous dinosaurs to have formed a natural group. Huene abandoned the name "Theropoda", instead using Harry Seeley 's Order Saurischia , which Huene divided into
11514-783: The shape of the tooth or denticles . The morphology of the teeth is distinct enough to tell the major families apart, which indicate different diet strategies. An investigation in July 2015 discovered that what appeared to be "cracks" in their teeth were actually folds that helped to prevent tooth breakage by strengthening individual serrations as they attacked their prey. The folds helped the teeth stay in place longer, especially as theropods evolved into larger sizes and had more force in their bite. Mesozoic theropods were also very diverse in terms of skin texture and covering. Feathers or feather-like structures (filaments) are attested in most lineages of theropods (see feathered dinosaur ). However, outside
11628-402: The shoulder). In contrast, abelisaurids had a large and bulbous humeral head (although similarly rounded) while that of other theropods was flattened from front to back. The leg is also somewhat characteristic in members of this family. The tibia (large innermost bone of the lower leg) was flattened from the front near the foot, although it was rounded further up the leg. As in other theropods,
11742-491: The suborders Coelurosauria and Pachypodosauria . Huene placed most of the small theropod groups into Coelurosauria, and the large theropods and prosauropods into Pachypodosauria, which he considered ancestral to the Sauropoda (prosauropods were still thought of as carnivorous at that time, owing to the incorrect association of rauisuchian skulls and teeth with prosauropod bodies, in animals such as Teratosaurus ). Describing
11856-430: The synapomorphies of the clade included "Keel or carinae in the postaxial cervical centra, absence of hyposphene-hypantra in caudal vertebrae (reversal to the plesiomorphic theropodan condition), a prominent dorsomedial process on the semilunate carpal, a convex ventral margin of the pubic foot, a subrectangular distal end of tibia and a sulcus along the posterior margin of the proximal end of fibula." Another proposed clade
11970-483: The teeth in the mouth were similar to the teeth of more conventional theropods. The rest of the body was also more similar to that of conventional theropods, with a neck, arms, and legs of moderate length. At least one noasaurine, the eponymous Noasaurus , had a large and deeply curved "sickle-shaped" claw of the hand. The diet of noasaurines is difficult to determine, with hypotheses ranging from fish to insects or other small animals. Rauhut & Carrano (2016) found only
12084-469: The theropod dinosaurs were the carnivorous Eodromaeus and, possibly, the herrerasaurids of Argentina . The herrerasaurs existed during the early late Triassic (Late Carnian to Early Norian ). They were found in North America and South America and possibly also India and Southern Africa. The herrerasaurs were characterised by a mosaic of primitive and advanced features. Some paleontologists have in
12198-408: The way theropods have often been reconstructed in art and the popular media, the range of motion of theropod forelimbs was severely limited, especially compared with the forelimb dexterity of humans and other primates . Most notably, theropods and other bipedal saurischian dinosaurs (including the bipedal prosauropods ) could not pronate their hands—that is, they could not rotate the forearm so that
12312-603: The wrist not seen in other theropods, thanks to the presence of a specialized half-moon shaped wrist bone (the semi-lunate carpal) that allowed the whole hand to fold backward towards the forearm in the manner of modern birds. In 2001, Ralph E. Molnar published a survey of pathologies in theropod dinosaur bone. He found pathological features in 21 genera from 10 families. Pathologies were found in theropods of all body size although they were less common in fossils of small theropods, although this may be an artifact of preservation. They are very widely represented throughout
12426-527: Was an island near Madagascar during the Cretaceous). In 2020 indeterminate remains were described from the Barremian-Aptian and Cenomanian of Australia. Members of this subfamily are definitively part of Noasauridae, although this group may not necessarily be elevated to subfamily status whenever elaphrosaurines are found to be outside of Noasauridae. Many members of this subfamily are quite fragmentary, and as
12540-423: 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
12654-408: Was gone by the late Triassic. Digit I is reduced and generally do not touch the ground, and greatly reduced in some lineages. They also lack a digit V on their hands and have developed a furcula which is otherwise known as a wishbone. Early neotheropods like the coelophysoids have a noticeable kink in the upper jaw known as a subnarial gap. Averostrans are some of the most derived theropods and contain
12768-460: Was named by Thomas Holtz , who defined it as "the most recent common ancestor of Ornithomimus and birds , and all descendants of that common ancestor." One of the possible synapomorphies of this clade is the presence of feathers homologous to those of birds, based on study of a specimen of Shuvuuia . The following family tree illustrates a synthesis of the relationships of the major coelurosaurian groups based on various studies conducted in
12882-544: Was referred to Elaphrosaurinae. This is the first evidence of Elaphrosaurinae from Australia. The following cladogram is based on the phylogenetic analysis conducted by Rauhut and Carrano in 2016, showing the relationships among the Noasauridae: Abelisauridae Laevisuchus Deltadromeus Limusaurus CCG 20011 Elaphrosaurus Velocisaurus Noasaurus Masiakasaurus Even in recent studies,
12996-423: Was swimming near the surface of a river and just the tips of its toes and claws could touch the bottom. The tracks indicate a coordinated, left-right, left-right progression, which supports the proposition that theropods were well-coordinated swimmers. During the late Triassic , a number of primitive proto-theropod and theropod dinosaurs existed and evolved alongside each other. The earliest and most primitive of
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