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65-558: The bushwren ( Xenicus longipes ), also known as the mātuhituhi in the Māori language , was a very small and almost flightless bird that was endemic to New Zealand . It had three subspecies on each of the major islands of New Zealand, the North Island , South Island , and Stewart Island / Rakiura and nearby smaller islands. The species disappeared gradually after the introduction of invasive mammalian predators, last being seen on

130-733: A clade consisting of Falconidae , Psittaciformes and Passeriformes . The following cladogram follows the analysis of Degrange and colleagues, 2015:   Mesembriornis incertus   Mesembriornis milneedwardsi   Llallawavis scagliai   Procariama simplex   Psilopterus affinis   Psilopterus bachmanni   Psilopterus colzecus   Psilopterus lemoinei   Kelenken guillermoi   Devincenzia pozzi   Titanis walleri   Phorusrhacos longissimus   Andalgalornis steulleti   Andrewsornis abbotti   Patagornis marshi   Physornis fortis   Paraphysornis brasiliensis During

195-692: A 71-centimetre (28 in), nearly intact skull. The beak is roughly 46 cm (18 in) long and curves in a hook shape that resembles an eagle's beak. Most species described as phorusrhacid birds were smaller, 60–90 cm (2.0–3.0 ft) tall, but the new fossil belongs to a bird that probably stood about 3 m (9.8 ft) tall. Scientists theorize that the large terror birds were extremely nimble and quick runners, able to reach speeds of 48 km/h (30 mph). Examination of phorusrhacid habitats also indicates that phorusrhacids may have presented intense competition to predatory metatherian sparassodonts such as borhyaenids and thylacosmilids , causing

260-864: A claimed territory selected for large size and cursoriality in Tertiary ancestors of ratites. Temperate rainforests dried out throughout the Miocene and transformed into semiarid deserts, causing habitats to be widely spread across the growingly disparate landmasses. Cursoriality was an economic means of traveling long distances to acquire food that was usually low-lying vegetation, more easily accessed by walking. Traces of these events are reflected in ratite distribution throughout semiarid grasslands and deserts today. Gigantism and flightlessness in birds are almost exclusively correlated due to islands lacking mammalian or reptilian predators and competition. However, ratites occupy environments that are mostly occupied by

325-412: A diverse number of mammals. It is thought that they first originated through allopatric speciation caused by breakup of the supercontinent Gondwana . However, later evidence suggests this hypothesis first proposed by Joel Cracraft in 1974 is incorrect. Rather ratites arrived in their respective locations via a flighted ancestor and lost the ability to fly multiple times within the lineage. Gigantism

390-643: A downward strike, its developed neck muscles and heavy head could produce enough momentum and power to cause fatal damage to the terror bird's prey. Kelenken guillermoi , from the Langhian stage of the Miocene epoch, some 15 million years ago, discovered in the Collón Curá Formation in Patagonia in 2006, represents the largest bird skull yet found. The fossil has been described as being

455-402: A greater extreme, the terror birds (and their relatives the bathornithids ), eogruids , geranoidids , gastornithiforms , and dromornithids (all extinct) all evolved similar body shapes – long legs, long necks and big heads – but none of them were closely related. Furthermore, they also share traits of being giant, flightless birds with vestigial wings, long legs, and long necks with some of

520-643: A large, sharp beak, a powerful neck and sharp talons. However, even with these attributes, the phorusrhacids are often assumed to have preyed on relatively small animals (about the size of a rabbit) that could be dispatched with a minimum of struggle. This is because with the phorusrhacids' beak proportions, the jaw could not generate a great deal of bite force with which to kill the prey. This is disputable as many big-game hunting predators such as Smilodon , great white sharks and Allosaurus have weaker bite forces and often laterally weak skulls as adaptations towards, not away from, killing large prey, relying instead on

585-502: A limited number of times per year. High parental involvement denotes the necessity for choosing a reliable mate. In a climatically stable habitat providing year-round food supply, a male's claimed territory signals to females the abundance of resources readily available to her and her offspring. Male size also indicates his protective abilities. Similar to the emperor penguin, male ratites incubate and protect their offspring anywhere between 85 and 92 days while females feed. They can go up to

650-466: A more efficient use of energy in adulthood. The name "ratite" comes from the Latin ratis , raft, a vessel with no keel . Their flat sternum is distinct from the typical sternum of flighted birds because it lacks a keel, like a raft. This structure is the place where flight muscles attach and thus allow for powered flight. However, ratite anatomy presents other primitive characters meant for flight, such as

715-532: A nearly spherical mass with the skull in the center" that resembled giant owl pellets , suggesting that phorusrhacids may have swallowed their prey whole and regurgitated the indigestible parts similar to owls . However, Ameghino never formally described these specimens and they have not yet been relocated, making it difficult to determine if they are phorusrhacid pellets. Fossilized pellets from northwestern Argentina have also been suggested to pertain to small phorusrhacids like Procariama . The etymology of

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780-554: A parachute apparatus to help the bird slow down. Wings are hypothesized to have played a role in sexual selection in early ancestral ratites and were thus maintained. This can be seen today in both the rheas and ostriches. These ratites utilize their wings extensively for courtship and displays to other males. Sexual selection also influences the maintenance of large body size, which discourages flight. The large size of ratites leads to greater access to mates and higher reproductive success . Ratites and tinamous are monogamous and mate only

845-600: A smaller subspecies of this bird was also found recently. With this fossil, it was found that the internal structure of the beak is hollow and reinforced with thin-walled trabeculae . There is also an absence of both zona flexoria palatina and zona flexoria arcus jugalis, which are key features that relate to the evolution of cranial akinesis . The discovery of this skull allows for the establishment of primary osteological homologies, which are useful in comparative anatomy, functional morphology, and phylogenetic studies. Most phorusrhacids were very fast runners. All members possessed

910-637: A specimen of Psilopterus dating to 96,040 ± 6,300 years ago would imply that phorusrhacids survived in South America until the late Pleistocene . Phorusrhacids may have even made their way into Africa and Europe , if the genus Lavocatavis from Algeria and Eleutherornis from France and Switzerland are included. However, the taxonomic placement of both taxa within phorusrhacids are considered highly questionable, and their remains are too fragmentary to be included in phylogenetic analyses. Possible specimens have also been discovered from

975-505: A trackway made by a mid-to-large sized terror bird with functionally didactyl footprints, the inner toe with the sickle claw raised mostly off the ground akin to their Mesozoic counterparts. In the past, these birds were thought to have high beaks, round orbits , and vaulted braincases though there was never enough empirical evidence to support this. However, new fossils have been discovered in Comallo, Argentina. These skulls reveal that

1040-416: A week without eating and survive only off fat stores. The emu has been documented fasting for as long as 56 days. If no continued pressures warrant the energy expenditure to maintain the structures of flight, selection will tend towards these other traits. In penguins , wing structure is maintained for use in locomotion underwater. Penguins evolved their wing structure to become more efficient underwater at

1105-416: Is likely because penguins have well-developed pectoral muscles for hunting and diving in the water. For ground-feeding birds, a cursorial lifestyle is more economical and allows for easier access to dietary requirements. Flying birds have different wing and feather structures that make flying easier, while flightless birds' wing structures are well adapted to their environment and activities, such as diving in

1170-411: Is not a requirement for flightlessness. The kiwi do not exhibit gigantism, along with tinamous , even though they coexisted with the moa and rheas that both exhibit gigantism. This could be the result of different ancestral flighted birds arrival or because of competitive exclusion. The first flightless bird to arrive in each environment utilized the large flightless herbivore or omnivore niche, forcing

1235-431: Is often why flightlessness coincides with body mass. By reducing large pectoral muscles that require a significant amount of overall metabolic energy, ratites decrease their basal metabolic rate and conserve energy. A study looking at the basal rates of birds found a significant correlation between low basal rate and pectoral muscle mass in kiwis. On the contrary, flightless penguins exhibit an intermediate basal rate. This

1300-491: Is that until the arrival of humans roughly a thousand years ago, there were no large mammalian land predators in New Zealand; the main predators of flightless birds were larger birds. Ratites belong to the superorder Palaeognathae , which include the volant tinamou , and are believed to have evolved flightlessness independently multiple times within their own group. Some birds evolved flightlessness in response to

1365-558: The Ameghinornithidae from Europe in the phorusrhacoids; these have meanwhile turned out to be more basal members of Cariamae. Though traditionally considered as members of the Gruiformes , based on both morphological and genetic studies (the latter being based on the seriema ) Cariamiformes may belong to a separate group of birds, Australaves , and their closest living relatives, according to nuclear sequence studies, are

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1430-548: The Broad Breasted White turkey , have become totally flightless as a result of selective breeding ; the birds were bred to grow massive breast meat that weighs too much for the bird's wings to support in flight. Flightlessness has evolved in many different birds independently, demonstrating repeated convergent evolution. There were families of flightless birds, such as the now-extinct Phorusrhacidae , that evolved to be powerful terrestrial predators. Taking this to

1495-654: The Early Eocene . They ranged in height from 1 to 3 m (3 to 10 ft). One of the largest specimens from the Early Pleistocene of Uruguay , possibly belonging to Devincenzia , would have weighed up to 350 kilograms (770 lb). Their closest modern-day relatives are believed to be the 80-centimetre-tall (31 in) seriemas . Titanis walleri , one of the larger species, is known from Texas and Florida in North America . This makes

1560-821: The Gastornithidae , the Dromornithidae , the Palaeognathae , and the Phorusrhacidae. Phorusrhacids are an extinct group within Cariamiformes , the only living members of which are the two species of seriemas in the family Cariamidae. While they are the most taxon-rich group within Cariamiformes, the interrelationships between phorusrhacids are unclear due to the incompleteness of their remains. A lineage of related predatory birds,

1625-655: The Holocene (no more than 11,000 years ago). Extinct species are indicated with a cross (†). A number of species suspected, but not confirmed to be flightless, are also included here. Longer-extinct groups of flightless birds include the Cretaceous patagopterygiformes , hesperornithids , the Cenozoic phorusrhacids ("terror birds") and related bathornithids , the unrelated eogruids , geranoidids , gastornithiforms , and dromornithids (mihirungs or "demon ducks"), and

1690-611: The La Meseta Formation of Seymour Island , Antarctica , suggesting that this group had a wider geographical range in the Paleogene . The closely related bathornithids occupied a similar ecological niche in North America across the Eocene to Early Miocene ; some, like Paracrax , were similar in size to the largest phorusrhacids. At least one analysis recovers Bathornis as sister taxa to phorusrhacids, on

1755-813: The bathornithids , occupied North America prior to the arrival of phorusrhacids, living from the Eocene to Miocene and filled a similar niche to phorusrhacids. Only one genus belongs in the family, Bathornis , according to a 2016 analysis by paleontologist Gerald Mayr, who noted that Bathornis was more lightly built, with longer limbs proportionally and skulls more akin to those of Cariama . Phylogenetic analysis of Cariamiformes and their relatives according to Mayr (2016) in his redescription of Bathornis : A 2024 study finds Bathornis as closer to seriemas than phorusrhacids were. Opisthocomidae Paracrax Elaphrocnemus Bathornis Ameghinornis Dynamopterus Cariama Phorusrhacidae Following

1820-713: The plotopterids . Phorusrhacidae Phorusrhacids , colloquially known as terror birds , are an extinct family of large carnivorous , mostly flightless birds that were among the largest apex predators in South America during the Cenozoic era. Their definitive fossil records range from the Middle Eocene to the Late Pleistocene around 43 to 0.1 million years ago , though some specimens suggest that they were present since

1885-612: The 20th century in the Huiarau Range and from Kapiti Island in 1911. Apparently, the last population lived in the area where Te Urewera National Park was established, just around the time of its extinction. The last authenticated reports of the South Island subspecies ( X. l. longipes ) were from Arthur's Pass in 1966 and Nelson Lakes National Park in 1968. There have been a few unsubstantiated reports since then from Fiordland and Nelson Lakes. The third subspecies,

1950-588: The Cenozoic and competed successfully for a time with large carnivorans such as nimravids , before becoming extinct in the Early Miocene, about 20 million years ago. The phorusrhacid Titanis expanded northward into southern North America during the Interchange and coexisted for several million years with large canids and big cats like Xenosmilus , before its extinction about 1.8 million years ago. There were some suggestions that phorusrhacids, like

2015-682: The Miocene and early Pliocene epochs, there was an increase in the phorusrhacid population size in South America, suggesting that, in that time frame, the various species flourished as predators in the savanna environment. With the emergence of the Isthmus of Panama 2.7 million years ago, carnivorous dogs, bears, and cats from North America were able to cross into South America, increasing competition. (They had been preceded by procyonids as early as 7.3 million years ago. ) The population of phorusrhacids declined thereafter according to older hypotheses, suggesting that competition with newly arrived predators

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2080-551: The North Island in 1955 and the South Island in 1968. Attempts were made to save the remaining population on small islands off Stewart Island, but they ultimately failed with the death of the last remaining known birds in 1972. German naturalist Johann Friedrich Gmelin described the bushwren in 1789. It grew to about 9 cm long and 16 g in weight. It fed mostly on invertebrates , which it captured by running along

2145-569: The Stewart Island bushwren or Stead's bushwren ( X. l. variabilis ), was found on Stewart Island / Rakiura and nearby islands. It is known to have survived on Stewart Island until 1951, but was probably exterminated there by feral cats . It lived on Kotiwhenua (Solomon) Island , being reasonably common, until the early 1960s. It survived on predator-free Taukihepa / Big South Cape Island until black rats ( R. rattus ) invaded it in 1964. The New Zealand Wildlife Service attempted to save

2210-413: The ability to fly. They are, however, weak fliers and are incapable of traveling long distances by air. Although selection pressure for flight was largely absent, the wing structure has not been lost except in the New Zealand moas. Ostriches are the fastest running birds in the world and emus have been documented running 50 km/h. At these high speeds, wings are necessary for balance and serving as

2275-404: The absence of predators, for example on oceanic islands . Incongruences between ratite phylogeny and Gondwana geological history indicate the presence of ratites in their current locations is the result of a secondary invasion by flying birds. It remains possible that the most recent common ancestor of ratites was flightless and the tinamou regained the ability to fly. However, it is believed that

2340-403: The basis of shared features in the jaws and coracoid , though this has been seriously contested, as these might have evolved independently for the same carnivorous, flightless lifestyle. The neck can be divided into three main regions. In the higher regions of the neck, the phorusrhacid has bifurcate neural spines (BNS), while it has high neural spines in its lower regions. This suggests that

2405-437: The beak as a blade to strike at or slash vital organs. It has been recently shown that at least some phorusrhacids like Andalgalornis , while very fast runners in a straight line, were poor at tight turns at speed, which contradicts the idea of phorusrhacids being agile predators of small prey. All phorusrhacids are thought to have been carnivorous. The strong downwards curve from the tip of this beak suggests that it ripped

2470-458: The beak more resilient to force from the front to back direction, thus suggesting that it could cause a great amount of harm through pecking as opposed to side-to-side head movements like shaking prey. Generally speaking, it is thought that a terror bird would use its feet to injure prey by kicking it, and to hold the prey down and dispatch by pecking at it with its large beak. Larger prey may also have been attacked by pecking and kicking, or by using

2535-485: The bottom of the fossil-containing stratum), which would extend the existence of the smaller members of this group of avian predators considerably. Another unidentified smaller type which may be a possible psilopterine from the La Paz Local Fauna of Uruguay has also been dated to the late Pleistocene, perhaps 17,620 ± 100 years ago based on radiocarbon analysis using accelerator mass spectrometry (AMS) for

2600-472: The branches of trees. It nested on or near the ground. Bushwrens had a hopping or bobbing movement, with a fast running speed on the ground or branches. Their call was a 'subdued trill' or 'seep', sometimes repeated in quick succession. They built spherical nests near the ground with an entrance on the side, and typically laid two eggs in November or December. It was widespread throughout the main islands of

2665-453: The cost of their efficiency in the air. The only known species of flightless bird in which wings completely disappeared was the gigantic, herbivorous moa of New Zealand , hunted to extinction by humans by the 15th century. In moa, the entire pectoral girdle is reduced to a paired scapulocoracoid , which is the size of a finger. Many flightless birds are extinct ; this list shows species that are either still extant or became extinct in

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2730-457: The country until the late 19th century when mustelids were introduced and joined rats as invasive mammalian predators. The only authenticated reports of the North Island subspecies ( X. l. stokesi ) since 1900 were from the southern Rimutaka Range in 1918 and the Ureweras up to 1955, with probable sightings on June 13, 1949, near Lake Waikareiti , and several times in the first half of

2795-509: The earlier-arriving procyonids, which evolved to large body size in South America, but these were omnivorous ), with native South American predator lineages (including most phorusrhacids and all sparassodonts and sebecids) dying out well before the arrival of most larger placental carnivores. Bathornithids , which were similar in ecology and are likely close relatives of phorusrhacids, existed entirely within North America during part of

2860-473: The evolution of flightlessness hypothesized intraspecific competition selected for a reduced individual energy expenditure, which is achieved by the loss of flight. Some flightless varieties of island birds are closely related to flying varieties, implying flight is a significant biological cost . Flight is the most costly type of locomotion exemplified in the natural world. The energy expenditure required for flight increases proportionally with body size, which

2925-627: The flesh from the body of other animals; many extant bird species with this feature are carnivorous. CT scans performed on the skull of a phorusrhacid reveal that the species would not have been able to shake its prey side to side, but rather exert significant downward force. Florentino Ameghino claimed in a letter to Édouard Trouessart that he had specimens from Argentina of "petrified masses preserving skeletons of large rodents, Interatheriidae [small notoungulates ] and even Proterotheriidae [deer-sized litopterns ], with all their bones crushed and corroded, piled on with no apparent order and forming

2990-402: The fusion of wing elements, a cerebellar structure, the presence of a pygostyle for tail feathers, and an alula on the wing. These morphological traits suggest some affinities to volant groups. Palaeognathes were one of the first colonizers of novel niches and were free to increase in abundance until the population was limited by food and territory. A study looking at energy conservation and

3055-510: The later arrivals to remain smaller. In environments where flightless birds are not present, it is possible that after the K/T Boundary there were no niches for them to fill. They were pushed out by other herbivorous mammals . New Zealand had more species of flightless birds (including the kiwi , several species of penguins , the takahē , the weka , the moa, and several other extinct species ) than any other such location. One reason

3120-411: The living families of Cariamidae and Sagittariidae , but their differences in body mass are too drastic and, thus, one cannot overly depend on these living families for answers. During the early Cenozoic , after the extinction of the non-bird dinosaurs , mammals underwent an evolutionary diversification , and some bird groups around the world developed a tendency towards gigantism ; this included

3185-475: The loss of flight is an easier transition for birds than the loss and regain of flight, which has never been documented in avian history. Moreover, tinamou nesting within flightless ratites indicates ancestral ratites were volant and multiple losses of flight occurred independently throughout the lineage. This indicates that the distinctive flightless nature of ratites is the result of convergent evolution. Two key differences between flying and flightless birds are

3250-503: The majority of Pleistocene megafauna, were killed off by human activity such as hunting or habitat change. This idea is no longer considered valid, as improved dating on Titanis specimens show that the last phorusrhacids went extinct over one million years before humans arrived. However, several fossil finds of smaller forms have been described from the late Pleistocene of Uruguay in South America. Psilopterus may have been present until 96,040 ± 6,300 years ago (maximum age obtained from

3315-462: The mammalian predators to choose forested habitats to avoid the more successful and aggressive avian predators on the open plains. The feet of the phorusrhacids had four toes, the first of which, known as the hallux , was reduced and did not touch the ground, while the others, corresponding to the second, third and fourth toes, were kept on the ground. Analysis of the resistance of the toes based on biomechanical models of curved beams, in particular of

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3380-464: The name Phorusrhacidae is based on the type genus Phorusrhacos . When first described by Florentino Ameghino in 1887, the etymology of Phorusrhacos was not given. Current thinking is that the name is derived from a combination of the Greek words "phoros", which means bearer or bearing , and "rhakos", which translates to wrinkles , scars or rents . Researchers have compared Phorusrhacidae with

3445-430: The ocean. Species with certain characteristics are more likely to evolve flightlessness. For example, species that already have shorter wings are more likely to lose flight ability. Some species will evolve flatter wings so that they move more efficiently underwater at the cost of their flight. Additionally, birds that undergo simultaneous wing molt, in which they replace all of the feathers in their wings at once during

3510-441: The phorusrhacid had a highly flexible and developed neck allowing it to carry its heavy head and strike with terrifying speed and power. Although the phorusrhacid externally looks like it has a short neck, its flexible skeletal neck structure proves that it could expand farther beyond the expected reach and intimidate its prey using its height, allowing it to strike more easily. Once stretched out into its full length in preparation for

3575-662: The phorusrhacids the only known large South American predator to migrate north in the Great American Interchange that followed the formation of the Isthmus of Panama land bridge (the main pulse of the interchange began about 2.6 Ma ago; Titanis at 5 Ma was an early northward migrant). It was once believed that T. walleri became extinct in North America around the time of the arrival of humans, but subsequent datings of Titanis fossils provided no evidence for their survival after 1.8 Ma. However, reports from Uruguay of new findings of phorusrachids such as

3640-431: The presence of a cutting edge, a wide gape made possible by the reduction of jaw musculature, and the driving force of the body or neck. Since phorusrhacids share many of the same adaptations, such as a large, laterally flattened skull with a sharp-edged beak and powerful neck musculature, it is possible that they were specialized predators of relatively large prey. The bones of the beak were tightly fused together, making

3705-642: The ratites, although they are not related. Divergences and losses of flight within ratite lineage occurred right after the K-Pg extinction event wiped out all non-avian dinosaurs and large vertebrates 66 million years ago. The immediate evacuation of niches following the mass extinction provided opportunities for Palaeognathes to distribute and occupy novel environments. New ecological influences selectively pressured different taxa to converge on flightless modes of existence by altering them morphologically and behaviorally. The successful acquisition and protection of

3770-447: The revision by Alvarenga and Höfling (2003), there are now 5 subfamilies , containing 14 genera and 18 species : These species were the product of adaptive radiation. The following classification is based on LaBarge, Garderner & Organ (2024), and taxa identified as incertae sedis were all excluded from phylogenetic analysis in their study (except for Brontornis ): Family Phorusrhacidae Alvarenga and Höfling did not include

3835-406: The second toe and its nail claw, indicate that it was modified into a "sickle claw" and was relatively uniform in various species and said claw would be relatively curved and large, which implies the need to keep it elevated to avoid wear or breakage due to contact with the ground, which would be achieved with a well-developed extensor tubercle and soft tissue pads on the fingers. The second toe, which

3900-513: The smaller wing bones of flightless birds and the absent (or greatly reduced) keel on their breastbone, which anchors muscles needed for wing movement. Adapting to a cursorial lifestyle causes two inverse morphological changes to occur in the skeleto-muscular system: the pectoral apparatus used to power flight is paedorphically reduced while peramorphosis leads to enlargement of the pelvic girdle for running. Repeated selection for cursorial traits across ratites suggests these adaptions comprise

3965-496: The species by relocating all the birds they could capture. They caught six birds and transferred them to Kaimohu Island , where they did not survive and they finally died out in 1972. Flightless bird Many domesticated birds, such as the domestic chicken and domestic duck , have lost the ability to fly for extended periods, although their ancestral species, the red junglefowl and mallard , respectively, are capable of extended flight. A few particularly bred birds, such as

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4030-492: The terror bird has a triangular dorsal view, a rostrum that is hooked and more than half the length of the actual skull, and a more compact caudal portion. The external nares and antorbital fenestras (areas found in the nose) were found to be more square than triangular. These all contribute to a skull that is more rectangular in view rather than triangular. The structure of the fossils also suggest that these birds may have been swifter than originally thought. A skull from

4095-575: The year, are more likely to evolve flight loss. A number of bird species appear to be in the process of losing their powers of flight to various extents. These include the Zapata rail of Cuba , the Okinawa rail of Japan , and the Laysan duck of Hawaii . All of these birds show adaptations common to flightlessness, and evolved recently from fully flighted ancestors, but have not yet completely given up

4160-549: Was a major contributor to their extinction. Similar ideas have been considered for sparassodonts and for South America's terrestrial sebecid crocodilians. However, the role of competitive displacement in South American predator lineages has been questioned by some researchers. The timing of turnover events and the decline of South American predators do not correlate well with the arrival of large carnivores like canids or sabretooths (although they do correlate well with

4225-547: Was shorter and had fewer phalanges, also had more resistance and would make it easier to hold the claw off the ground and retain prey, a compromise with its predatory function and movement on the run, as occurs with modern seriemas, although to a lesser degree of specialization than dromaeosaurid dinosaurs. This is further supported by footprints from the Late Miocene of the Río Negro Formation , showcasing

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