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98-462: Paraves are a widespread group of theropod dinosaurs that originated in the Middle Jurassic period. In addition to the extinct dromaeosaurids , troodontids , anchiornithids , and possibly the scansoriopterygids , the group also contains the avialans , which include diverse extinct taxa as well as the over 10,000 species of living birds . Basal members of Paraves are well known for
196-695: 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
294-414: A natural group . The name 'Paraves' (Greek pará , par' 'beside, near' + Latin aves , plural of avis 'bird') was coined by Sereno in 1997. The clade was defined by Sereno in 1998 as a branch-based clade containing all Maniraptora closer to Neornithes (which includes all the birds living in the world today) than to Oviraptor . A node-based clade called Eumaniraptora ("true maniraptorans")
392-435: A tubercle , for ligamentous attachment. Its plantar surface is grooved antero-posteriorly for the passage of the flexor tendons , and marked on either side by an articular eminence continuous with the terminal articular surface. During growth, the growth plates are located distally on the metatarsals, except on the first metatarsal where it is located proximally. Yet it is quite common to have an accessory growth plate on
490-461: 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
588-538: A clade (all theropods closer to dromaeosaurids than to birds) by Jacques Gauthier in 1986. However, several more recent studies have cast doubt on the hypothesis that dromaeosaurids and troodontids were more closely related to each other than either was to birds, instead finding that troodontids were more closely related to birds than to dromaeosaurids. Because Deinonychosauria was originally defined as all animals closer to dromaeosaurids than to birds without specific reference to troodontids, this would render Deinonychosauria
686-484: A clade including Troodontidae and Avialae . In 2015 Chatterjee created Tetrapterygidae in the second edition of his book The Rise of Birds: 225 Million Years of Evolution , where he included Microraptor , Xiaotingia , Aurornis , and Anchiornis ; together they were proposed to be the sister group of the Avialae . Paraves , Eumaniraptora , and Averaptora are often considered to be synonyms, depending on
784-537: 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
882-557: 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 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
980-416: 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
1078-457: 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
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#17327934806051176-476: 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 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
1274-416: 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
1372-421: A second set of airfoils. These species, most famously represented by Microraptor gui , have often been referred to as "four winged dinosaurs". Though it has been suggested that these hind wings would have prevented some paravians from getting around on the ground, and that they must have lived in trees, there is very little evidence that any of the earliest paravians were capable of climbing. This apparent paradox
1470-410: 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
1568-478: 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
1666-425: 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
1764-538: 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
1862-613: A synonym of Dromaeosauridae. The clade containing avialans, microraptorians, unenlagiids, Anchiornis , and Xiaotingia to the exclusion of Eudromaeosauria was named Averaptora by Agnolín and Novas (2013), defined as all animals closer to Passer than to Dromaeosaurus . Most studies use a similar definition for Avialae , which Agnolín and Novas redefine as the least inclusive clade including Archaeopteryx and modern birds. Averaptora additionally contains troodontids according to Cau, Beyrand, Voeten et al . (2017) and other phylogenies in which find Eudromaeosauria to be an outgroup to
1960-406: 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
2058-408: Is wedge -shaped, articulating proximally with the tarsal bones, and by its sides with the contiguous metatarsal bones: its dorsal and plantar surfaces are rough for the attachment of ligaments . The head or distal extremity presents a convex articular surface, oblong from above downward, and extending farther backward below than above. Its sides are flattened, and on each is a depression, surmounted by
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#17327934806052156-463: Is a branch-based clade defined to include all dinosaurs which are more closely related to birds than to oviraptorosaurs . The ancestral paravian is the earliest common ancestor of birds, dromaeosaurids , and troodontids which was not also ancestral to oviraptorosaurs . Paraves often comprises three major sub-groups: Avialae , including Archaeopteryx and modern birds, as well as the dromaeosaurids and troodontids , which may or may not form
2254-468: 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
2352-487: 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
2450-525: Is harder to determine as bone mass only represents a small proportion of the total body mass of animals. One method 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
2548-470: 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
2646-512: 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
2744-507: 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-avialan 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, 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
2842-584: 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
2940-414: 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 Metatarsus The metatarsal bones or metatarsus ( pl. : metatarsi ) are a group of five long bones in
3038-605: 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
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3136-671: 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
3234-589: 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
3332-481: 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
3430-742: 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
3528-524: 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
3626-630: 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
3724-424: The midfoot , located between the tarsal bones (which form the heel and the ankle ) and the phalanges ( toes ). Lacking individual names, the metatarsal bones are numbered from the medial side (the side of the great toe ): the first , second , third , fourth , and fifth metatarsal (often depicted with Roman numerals ). The metatarsals are analogous to the metacarpal bones of the hand . The lengths of
3822-455: 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
3920-480: 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
4018-469: 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
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4116-681: 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
4214-466: 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,
4312-515: 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 (†)
4410-546: 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
4508-459: 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
4606-484: 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,
4704-431: The best-known features of paravians is the presence of an enlarged and strongly curved "sickle claw" on a hyper-extendible second toe, modified to hold the sickle claw clear of the ground when walking, most notably developed in the dromaeosaurids and troodontids. While this characteristic claw and its associated modifications to the anatomy of the foot (such as a shortened metatarsus in eudromaeosaurs ) had been known since
4802-679: The body mass continued to decrease in many forms within Avialae . Fossils show that all the earliest members of Paraves found to date started out as small, while Troodontidae and Dromaeosauridae gradually increased in size during the Cretaceous period. † Oviraptorosauria † Scansoriopterygidae † Xiaotingia † Yixianosaurus † Pedopenna † Aurornis † Serikornis † Eosinopteryx † Anchiornis † Troodontidae † Dromaeosauridae Avialae † Oviraptorosauria † Dromaeosauridae † Troodontidae † Anchiornithinae † Archaeopteryx † Scansoriopterygidae † Rahonavis Pygostylia Paraves
4900-417: The claws highly reduced or lost in some advanced lineages. An increasingly asymmetric wrist joint, a trend that can be traced back to primitive coelurosaurs , allowed the forelimbs to elongate and an elaboration of their plumage, traits that made the evolution of flapping flight possible. Many early members of Paraves had both well-developed wings and long feathers on the hind legs, which in some cases, formed
4998-499: 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
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#17327934806055096-449: The distal first metatarsal. The base of each metatarsal bone articulates with one or more of the tarsal bones at the tarsometatarsal joints , and the head with one of the first row of phalanges at the metatarsophalangeal joints . Their bases also articulate with each other at the intermetatarsal joints The metatarsal bones are often broken by association football (soccer) players. These and other recent cases have been attributed to
5194-474: The earlier study by Manning and colleagues was correct and that the "sickle claws" would have been ineffective as cutting weapons. They compared the claw and overall foot anatomy of various primitive species with modern birds to shed light on their actual function. Fowler and colleagues showed that many modern predatory birds also have enlarged claws on the second toes. In modern raptors, these claws are used to help grip and hold prey of sizes smaller than or equal to
5292-651: The early Jurassic 200 million years ago, and fossil evidence shows that this theropod line evolved new adaptations four times faster than other groups of dinosaurs, and was shrinking 160 times faster than other dinosaur lineages were growing. Turner et al . (2007) suggested that extreme miniaturization was ancestral for the clade, whose common ancestor has been estimated to have been around 65 centimetres (26 in) long and 600–700 grams (21–25 oz) in mass. In Eumaniraptora , both Dromaeosauridae and Troodontidae went later through four independent events of gigantism, three times in dromaeosaurids and once in troodontids, while
5390-421: 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
5488-619: 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
5586-556: The feet were not as specialized and the claws were not as large or as hooked. Additionally, the toe joints allowed more range of motion than the simple up-down movements of advanced dromaeosaurids. This makes it likely that these species specialized in smaller prey that could be pinned using only the inner toes, not requiring the feet to be as strong or sturdy. Extreme examples of miniaturization and progenesis are found in Paraves. The ancestors of Paraves first started to shrink in size in
5684-413: 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
5782-470: 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
5880-408: The first toe ( hallux ) was usually small and angled inward toward the center of the body, but only became fully reversed in more specialized members of the bird lineage. One species, Balaur bondoc , possessed a first toe which was highly modified in parallel with the second. Both the first and second toes on each foot of B. bondoc were held retracted and bore enlarged, sickle-shaped claws. One of
5978-533: The front edge of dromaeosaurid and troodontid teeth were very small and fine, while the back edge had serrations which were very large and hooked. Most of the earliest paravian groups were carnivorous, though some smaller species (especially among the troodontids and early avialans) are known to have been omnivores, and it has been suggested that an omnivorous diet was the ancestral state for this group, with strict carnivory evolving in some specialized lineages. Fossils also suggest that legs and feet covered with feathers
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#17327934806056076-407: The ground, while using shallow wing beats and tail movements to stabilize themselves. Other lines of evidence for this behavior include teeth which had large, hooked serrations only on the back edge (useful in pulling flesh upward rather than slicing it) and large claws on the wings (for greater maneuvering of prey while mantling it with the wings). In more primitive dromaeosaurids and in troodontids,
6174-621: 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
6272-429: The interpretation of paravian systematics. Deinonychosauria will become a synonym of Dromaeosauridae when troodontids are found to form a clade with Avialae, to the exclusion of Dromaeosauridae. Tetrapterygidae is a polyphyletic grouping of four-winged basal paravian genera. Paravians diverged from other maniraptorans around 165 Mya . Then, around 110–90 Mya, the ancestors of Neornithes (modern birds) split from
6370-422: 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
6468-414: 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 is longer than Tyrannosaurus , showing that Spinosaurus
6566-469: 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
6664-457: 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
6762-685: The lightweight design of modern football boots , which provide less protection to the foot. In 2010 some football players began testing a new sock that incorporated a rubber silicone pad over the foot to provide protection to the top of the foot. Stress fractures are thought to account for 16% of injuries related to sports participation, and the metatarsals are the bones most often involved. These fractures are sometimes called march fractures , based on their traditional association with military recruits after long marches. The second and third metatarsals are fixed while walking, thus these metatarsals are common sites of injury. The fifth metatarsal may be fractured if
6860-514: 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,
6958-484: The metatarsal bones in humans are, in descending order, second, third, fourth, fifth, and first. A bovine hind leg has two metatarsals. The five metatarsals are dorsal convex long bones consisting of a shaft or body, a base ( proximally ), and a head ( distally ). The body is prismoid in form, tapers gradually from the tarsal to the phalangeal extremity, and is curved longitudinally, so as to be concave below, slightly convex above. The base or posterior extremity
7056-406: The mid-20th century, their possible functions were the subject mainly of speculation, and few actual studies were published. Initial speculation regarded the claws as slashing implements used to disembowel large prey. In this scenario, the shortened upper foot would serve as an anchor point for powerful tendons to improve kicking ability. However, subsequent studies of the actual claw shape showed that
7154-404: 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
7252-660: 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
7350-560: 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
7448-407: 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
7546-478: The only known non-eumaniraptoran paravian. Since the 1960s, the dromaeosaurids and troodontids have often been classified together in a group or clade named the Deinonychosauria , initially based primarily on the presence of a retractable second toe with sickle-claw (now also known to be present in some avialans). The name Deinonychosauria was coined by Ned Colbert and Dale Russell in 1969, and defined as
7644-651: The other paravians. Other than the crown group of modern birds, which are direct descendants in the stem lineage of Paraves, there are no extant survivors or genetic material, so their entire phylogeny is inferred only from the fossil record. The prototypical fossil is Archaeopteryx , of which 11 specimens have been found , both complete and partial. [REDACTED] [REDACTED] Theropod 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 ,
7742-418: 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
7840-400: 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
7938-541: 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
8036-580: The possession of an enlarged claw on the second digit of the foot, which was held off the ground when walking in some species. A number of differing scientific interpretations of the relationships between paravian taxa exist. New fossil discoveries and analyses make the classification of Paraves an active subject of research. Like other theropods, all paravians are bipedal, walking on their two hind legs. The teeth of basal paravians were curved and serrated, but not blade-like except in some specialized species, such as Dromaeosaurus albertensis . The serrations on
8134-449: The predator, while the birds use their body weight to pin their prey to the ground and eat it alive. Fowler and colleagues suggested that this behavior is entirely consistent with the anatomy of advanced dromaeosaurids like Deinonychus , which had slightly opposing first toes and strong tendons in the toes and foot. This makes it likely that advanced dromaeosaurids also used their claws to puncture and grip their prey to aid in pinning it to
8232-439: 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
8330-468: 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
8428-426: The second toe off the ground in a hyperextended position, with only the third and fourth toes bearing the weight of the animal. This is called functional didactyly. The enlarged second toe bore an unusually large, curved sickle-shaped claw (held off the ground or 'retracted' when walking). This claw was especially large and flattened from side to side in the large-bodied predatory eudromaeosaurs . In these early species,
8526-787: 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
8624-496: 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
8722-476: 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
8820-458: The underside of the claw was only weakly keeled and would not have been an effective cutting instrument. Instead, it appeared to be more of a hooking implement. Manning et al. suggested in 2006 that the claws were similar to crampons and were used for climbing, and in the case of larger species or individuals, climbing up the flanks of very large prey. A larger study of sickle-claw function, published in 2011 by Fowler and colleagues, concluded that
8918-408: 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
9016-603: 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
9114-522: Was addressed by later studies which showed that early paravians like Microraptor were capable of flapping flight and powered launching from the ground into the air without relying on climbing. Microraptor in particular also seems to represent a case of flight evolving independently of the bird lineage within Paraves. Most theropods walked with three toes contacting the ground, but fossilized footprint tracks confirm that many basal paravians, including dromaeosaurids, troodontids, and some early avialans, held
9212-483: Was an ancestral condition, possibly having originated in the Coelurosauria , even if this trait was later lost in more advanced birds. Paravians generally have long, winged forelimbs, though these have become smaller in many flightless species and some extinct lineages that evolved before flight. The wings usually bore three large, flexible, clawed fingers in early forms. The fingers became fused and stiffened and
9310-408: 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
9408-488: Was named by Padian, Hutchinson, & Holtz (1997). They defined their clade to include only avialans and deinonychosaurs. Paraves and Eumaniraptora are generally considered to be synonyms, though some phylogenetic studies suggest that the two groups have a similar but not identical content; Agnolín and Novas (2011) recovered scansoriopterygids and alvarezsaurids as paravians that were not eumaniraptorans, while Turner, Makovicky, and Norell (2012) recovered Epidexipteryx as
9506-403: Was possibly 3 meters longer than Tyrannosaurus , though Tyrannosaurus could still be more massive than Spinosaurus . Specimens such as Sue and Scotty are both estimated to be the heaviest theropods known to science. There is still no clear explanation for why these animals grew so heavy and bulky compared to the land predators that came before and after them. The largest extant theropod
9604-423: 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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