This is an accepted version of this page
80-559: Brachyrostra (meaning "short snouts") is a clade within the theropod dinosaur family Abelisauridae . It includes the famous genera Carnotaurus , Abelisaurus , Aucasaurus as well as their close relatives from the Cretaceous Period of Argentina and Brazil plus Caletodraco from France . The group was first proposed in an analysis conducted by Juan Canale and colleagues in 2008. They found that all South American abelisaurids described up to that point grouped together as
160-695: 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
240-461: 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
320-530: 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
400-416: 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
480-452: 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
560-522: A hypertrophied caudofemoralis muscle, the primary locomotory muscle in theropods which was located in the tail and pulled the femur backwards. This enlarged caudofemoralis, giving them a speed estimate of 48–56 km/h (30–35 mph), allowed brachyrostrans to be one of the fastest-running large theropod groups yet known. Within Brachyrostra, there is a slightly more restrictive clade, called Furileusauria ("stiff back lizards"). They represent some of
640-416: 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
720-428: 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
800-410: 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
880-478: 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
SECTION 10
#1732858705298960-425: 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
1040-525: 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
1120-492: A sub-clade of Abelisauridae, which they named based on the relatively unusual shape of their skulls (in comparison with other theropods). They defined the clade Brachyrostra as "all the abelisaurids more closely related to Carnotaurus sastrei than to Majungasaurus crenatissimus ." Brachyrostrans were relatively lightly built compared to other large theropods, ranging in size from 6.1–7.8 m (20–26 ft) and 1400–2000 kg (1.6–2.3 short tons) in weight. They are considered
1200-406: 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
1280-468: 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
1360-482: 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
1440-467: 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
1520-512: 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
1600-565: 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
1680-408: 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
SECTION 20
#17328587052981760-485: 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 Distal Too Many Requests If you report this error to the Wikimedia System Administrators, please include
1840-592: 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
1920-647: 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
2000-584: 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
2080-956: The abelisaurid Llukalkan , Federico Gianechini and colleagues performed a phylogenetic analysis to test the affinities of the new taxon. The simplified strict consensus tree of the analysis is shown below. Similar results have been recovered by other analyses including Coria and colleagues (2002), Canale and colleagues (2008), and Cerroni and colleagues (2020). Kryptops [REDACTED] Genusaurus Arcovenator Rajasaurus [REDACTED] Indosaurus Majungasaurus [REDACTED] Xenotarsosaurus Dahalokely Rahiolisaurus Ilokelesia Ekrixinatosaurus [REDACTED] Skorpiovenator [REDACTED] Llukalkan Pycnonemosaurus Quilmesaurus [REDACTED] Viavenator [REDACTED] Carnotaurus [REDACTED] Aucasaurus [REDACTED] Abelisaurus Brachyrostrans were initially known exclusively from South America. Members of
2160-407: 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
2240-475: 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
2320-742: 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
2400-524: 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
2480-630: 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
Brachyrostra - Misplaced Pages Continue
2560-455: 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
2640-459: The tibia . A more restrictive clade within Furileusauria is the tribe Carnotaurini . This group is a node-based clade and was first proposed by paleontologists Rodolfo Coria , Luis Chiappe , and Lowell Dingus in 2002, being defined as a clade containing " Carnotaurus sastrei , Aucasaurus garridoi , their most recent common ancestor, and all of its descendants." The tribe Carnotaurini
2720-480: 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
2800-461: 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
2880-667: 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
2960-461: 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,
3040-510: 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 (†)
3120-546: 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
3200-459: 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
3280-484: 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,
Brachyrostra - Misplaced Pages Continue
3360-499: 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
3440-421: 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
3520-601: 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
3600-451: The exact same skull adaptations (short snout, small teeth, and a fortified occiput ) as the Jurassic theropod Allosaurus , which presumably preyed upon large animals by gradual jaw slashing. Mazzetta et al. 1998–1999 and Phil Currie et al. 2011 found Carnotaurus to be a swift-running predator with semicursorial adaptations such as femoral resistance against bending moments and
3680-413: 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
3760-470: 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
3840-901: The group have been unearthed from the Anacleto Formation , the Bajo de la Carpa Formation , the Candeleros Formation , the Huincul Formation , and possibly the Sir Fernandez field of the Allen Formation to the southeast. A single named taxon, Pycnonemosaurus is also known from the Cachoeira do Bom Jardim Formation in Mato Grosso , Brazil. The description of the French taxon Caletodraco ,
3920-526: 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,
4000-412: The homologous materials not yet found in all other abelisaurids being: "a very broad coracoid (coracoid maximum width three times the distance across the scapular glenoid area), a humerus with a large and hemispherical head, an extremely short ulna and radius (ulna to humerus ratio 1:3 or less), and frontal prominences (swells or horns) that are located laterally on the skull roof." In their description of
4080-608: 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
SECTION 50
#17328587052984160-408: The intervertebral articulation in dorsal vertebrae , a crescent-shaped morphology of the distal tip of the transverse processes in anterior and middle caudal vertebrae, transverse processes of anterior caudal vertebrae that is distally expanded and projected anteriorly, a convex external margin of the transverse processes in anterior caudal vertebrae, and a downturned process on the cnemial crest of
4240-598: The jaw structure in Carnotaurus was built for swift, rather than strong, bites, with adaptations for mandibular kinesis to assist in swallowing small prey items whole. Surprisingly, it exhibits a form of paracraniokinesis in which the dentary bone articulates against the surangular bone , further jointing the lower jaw and hypothetically allowing this animal a wider array of hunting strategies. However, in 1998 and 2009, Robert Bakker and Francois Therrien and colleagues contested this finding, stating that Carnotaurus had
4320-422: 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
4400-412: The larger brachyrostrans, with an average length of 7.1 ± 2.1 m (23.3 ± 6.9 ft). The taxon is a stem-based clade and is defined as the most inclusive clade containing Carnotaurus sastrei but not Ilokelesia aguadagrandensis , Skorpiovenator bustingorryi , or Majungasaurus crenatissimus . Synapomorphies of Furileusauria recovered by Filippi and colleagues include:
4480-544: 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
4560-464: 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
4640-457: 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
4720-453: 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,
4800-515: The most derived abelisaurids, with traits like very short, narrow skulls and extremely reduced forearms, even more so than other abelisaurids. Many brachyrostrans had horns or rugosities on the frontal and nasal bones, which have been interpreted as bearing cornified structures or dermal armor. Studies of the skull anatomy of the most well-known species, Carnotaurus sastrei , lead to debate over what type of prey these animals hunted. Studies by Mazzetta et al. in 1998, 2004, and 2009 suggest that
4880-404: 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
SECTION 60
#17328587052984960-660: 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
5040-553: 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
5120-492: 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
5200-407: 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
5280-418: 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
5360-400: 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
5440-531: 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
5520-408: The presence of a tip in the middle area of the posterior surface of the ventral process of the postorbital , the presence of a knob followed by a deep notch in the postorbital- squamosal contact, the absence of fenestra between the frontal and lacrimal bones, an anterior projection of the distal end of the cervical epiphophyses , a posterior margin of the postzygapophyses which is level with
5600-439: 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
5680-468: 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
5760-783: 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
5840-491: 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
5920-469: 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
6000-408: 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
6080-603: 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
6160-408: 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
6240-439: Was named in 2002 by Rodolfo Coria et al. in 2002 after their discovery of Aucasaurus garridoi . Their morphological definition of it is by several synapomorphies of the clade, with two ambiguous ones: "the presence of hyposphene–hypantrum articulations in the proximal and middle sections of the caudal series, and cranial processes in the epipophyses of the cervical vertebrae." They defined more ambiguous synapomorphies due to
6320-423: 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
6400-729: Was the first definitive evidence of the clade from outside South America. The Albian taxon Genusaurus , which also hails from France, may also represent a European member of this clade. If it is truly a brachyrostran, it would represent the oldest member of the clade. The enigmatic taxon Dahalokely , from Madagascar may also belong to Brachyrostra, although this remains uncertain. [REDACTED] [REDACTED] [REDACTED] [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 ,
#297702