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55-570: 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

110-730: 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

165-691: 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

220-787: A distinct family (Prothylacynidae), phylogenetic analyses have found that these animals do not represent a monophyletic group. The exact age of most Eocene species of sparassodonts is uncertain, given the lack of precise stratigraphic information associated with most specimens and the recent division of the Casamayoran SALMA into the Vacan and Barrancan SALMAs. Several other metatherian taxa have been suggested to be sparassodonts or closely related to sparassodonts. The australian Murgon taxa Archaeonothos has been noted as being similar to sparassodonts, but currently its relationships are not fully concluded. Carneiro (2018) recovered

275-642: 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

330-643: 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

385-528: 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

440-551: A separate side branch that split before the last common ancestor of all modern marsupials. A number of these mammalian predators closely resemble placental predators that evolved separately on other continents, and are cited frequently as examples of convergent evolution . They were first described by Florentino Ameghino , from fossils found in the Santa Cruz beds of Patagonia . Sparassodonts were present throughout South America's long period of "splendid isolation" during

495-599: 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

550-631: 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

605-503: 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

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660-469: A well defined nuchal crest . Sparassodonts spanned a wide range of body sizes, from 2.2-pound (1 kg) weasel or civet -like forms to Thylacosmilus , which was the size of a leopard . Along with the Australian thylacoleonids , sparassodonts include some of the largest metatherian carnivores. Sparassodonts have highly reduced epipubic bones (pelvic bones which support the pouch ), to

715-502: Is 3.1.3.4 3.1.3.4 , with three upper and lower incisors , one upper and lower canine , three upper and lower premolars , and four upper and lower molars in each half of either jaw. Proborhyaenids usually only have two lower incisors instead of three, except for Callistoe . Thylacosmylids have at least two upper and only two lower incisors (the uppers grew into elongated sabers ), and two upper and lower premolars. Some specimens of Borhyaena and Arctodictis are also missing

770-594: Is an unofficial sub-epoch in the international geologic timescale in chronostratigraphy , representing the earliest division of the Pleistocene Epoch within the ongoing Quaternary Period. It is currently estimated to span the time between 2.580 ± 0.005 Ma (million years ago) and 0.773 ± 0.005 Ma. The term Early Pleistocene applies to both the Gelasian Age and the Calabrian Age . While

825-556: 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

880-758: The Cenozoic ; during this time, they shared the niches for large warm-blooded predators with the flightless terror birds . Previously, it was thought that these mammals died out in the face of competition from "more competitive" placental carnivorans during the Pliocene Great American Interchange , but more recent research has showed that sparassodonts died out long before eutherian carnivores arrived in South America (aside from procyonids , which sparassodonts probably did not directly compete with). Sparassodonts have been referred to as borhyaenoids by some authors, but currently

935-819: 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,

990-608: 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

1045-809: 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

1100-452: The postorbital bar connecting the forehead to the cheek, thus framing the eye. They exhibit marked postorbital constriction . The orbital process (between the cheek and the eye socket) is usually diminished, though the zygomatic arch (the cheekbone) is strong. They feature a prominent sagittal crest along the midline of the flattened skull, the crest strength is quite variable among borhyaenids. They have an expanded occipital bone with

1155-1283: The " Gurlin Tsav skull " an unnamed metatherian known from a partial skull found in the Late Cretaceous Nemegt Formation of Mongolia. The following cladogram of sparassodont interrelationships is after Engelman et al. , 2020. Not all studies agree on the sister group relationship between Thylacosmilidae and Borhyaenidae recovered here, with other studies finding thylacosmilids to be within Proborhyaenidae . The relationships among hathliacynids are also relatively unstable. Allqokirus Mayulestes Patene Hondadelphys Stylocynus Cladosictis Acyon Sipalocyon Notogale Sallacyon Lycopsis longirostrus Lycopsis viverensis Lycopsis torresi Lycopsis padillai Prothylacynus Pharsophorus Borhyaena Australohyaena Arctodictis sinclairi Arctodictis munizi Callistoe Paraborhyaena Proborhyaena Eomakhaira Patagosmilus Thylacosmilus Within Metatheria ,

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1210-643: 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

1265-732: The Gelasian and the Calabrian have officially been defined by the International Union of Geological Sciences (IUGS) to effectively constitute the Early Pleistocene, the succeeding Chibanian and Tarantian ages have yet to be ratified. These proposed ages are unofficially termed the Middle Pleistocene and Late Pleistocene respectively. The Chibanian provisionally spans time from 773 ka to 126 ka, and

1320-569: The Holocene is subdivided into Preboreal , Boreal , Atlantic , Subboreal , and Subatlantic stages of the Blytt–Sernander time scale . There are many regional subdivisions for the Upper or Late Pleistocene; usually these represent locally recognized cold ( glacial ) and warm ( interglacial ) periods. The last glacial period ends with the cold Younger Dryas substage. The Early Pleistocene

1375-506: The Holocene, dates are relative to the year 2000 (e.g. Greenlandian began 11,700 years before 2000). For the beginning of the Northgrippian a date of 8,236 years before 2000 has been set. The Meghalayan has been set to begin 4,250 years before 2000. 'Tarantian' is an informal, unofficial name proposed for a stage/age to replace the equally informal, unofficial 'Upper Pleistocene' subseries/subepoch. In Europe and North America,

1430-735: 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

1485-646: The Tarantian from then until the definitive end of the whole Pleistocene, c. 9700 BC in the 10th millennium BC . Sparassodonta † Hathliacynidae † Hondadelphidae † Borhyaenidae † Proborhyaenidae † Thylacosmilidae Sparassodonta (from Greek σπαράσσειν [ sparassein ], to tear, rend; and ὀδούς , gen. ὀδόντος [ odous , odontos ], tooth) is an extinct order of carnivorous metatherian mammals native to South America, related to modern marsupials . They were once considered to be true marsupials, but are now thought to be

1540-401: 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

1595-436: 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

1650-457: 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

1705-483: 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

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1760-443: The buccal, or cheekward, side) and associated stylar cusps. In the lower molars, the trigonids (the buccal shearing side) have an inflated paracristid and marginalized or absent metaconid; and the talonid (the distal, or backendwards, crushing side) is either reduced or gone. Sparassodonts can be divided into six major groups; basal sparassodonts (?earliest Paleocene -late Miocene ), species that cannot be easily assigned to any of

1815-507: 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

1870-626: 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

1925-597: The genus Varalphadon from the Late Cretaceous of North America as a basal member of Sparassodonta. However, this interpretation of Varalphadon as a sparassodont has not been supported by later phylogenetic analyses, and most of the purported synapomorphies between Varalphadon and sparassodonts are not actually present in Varalphadon or have been suggested to be due to convergent evolution. Sparassodonts have sometimes been considered closely related to

1980-425: The last upper molar, showing that the presence of this tooth was variable in these species. Sparassodonta is characterized by dental synapomorphies that distinguish the group from other closely related mammals. Unequivocal traits uniting the earliest Sparassodonts include: In borhyaenids, only the third premolar was ever replaced in the animal's lifetime, similar to other metatherians. In thylacosmilids, only

2035-454: The latest review of the group, that of Prevosti and Forasiepi (2018), with additions from more recent studies. Although Mayulestes was originally described as a sparassodont, later phylogenetic analyses have shown that it most likely does not belong to this group; however more recent studies show it to be closely related to sparassodonts. Similarly, while basal borhyaenoids such as Lycopsis and Prothylacynus were once thought to belong to

2090-411: 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

2145-405: The lower third premolar was replaced. The cusps of the sparassodont molar correlate to a cutting function rather than a crushing one. In the upper molars, the paracone (on the lingual, or tongueward, side) is reduced and fused to the metacone (distal, towards the back of the mouth), inflating the postmetacrista (the lingual border of the metacone); and they almost always lack the stylar shelf (on

2200-502: 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

2255-461: 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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2310-428: The molar enamel samples of a proboscidean from the same site, but the validity of this previous radiocarbon dating has been considered highly questionable due to the enamel's lack of collagen; the tibia of Macrauchenia patachonica from the same site has been more precisely dated to a mean value of approximately 21,600 ± 1,000 years ago based on gamma spectrometry and radiocarbon dating. Early Pleistocene For

2365-463: 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

2420-528: The other sparassodont groups and whose teeth often exhibit adaptations for omnivory ; hathliacynids (late Oligocene -early Pliocene /late Pliocene), which range from a marten to a thylacine in size, and have long, fox-like muzzles and teeth strongly suited for carnivory ; basal borhyaenoids (middle Eocene -late Miocene), borhyaenoids which are unable to be easily classified into the families Borhyaenidae , Thylacosmilidae , or Proborhyaenidae and range in form and size; borhyaenids (early-late Miocene),

2475-441: 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

2530-659: 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

2585-452: The point that early analysis could not even find evidence for them. This is a characteristic shared with the Australian thylacine , and historically argued as a synapomorphy , though nowadays it is considered to have developed independently for poorly understood reasons. As with thylacines, it is very likely that they possessed long cartilaginous elements instead. The dental formula of sparassodonts varies considerably. In borhyaenids, it

2640-429: 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

2695-444: 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

2750-406: 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

2805-425: The sparassodont group most specialized for running, but not as much as living carnivorans or even thylacines ; proborhyaenids (middle Eocene-late Oligocene ), robust, wolverine -like forms with ever-growing upper and lower canines ; and thylacosmilids (early Miocene-late Pliocene), another terrestrially specialized group with ever-growing saber-like upper canines . The taxonomic classification below follows

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2860-570: The term Borhyaenoidea refers to a restricted subgroup of sparassodonts comprising borhyaenids and their close relatives. Almost all sparassodonts have an exceptionally shortened snout—most especially thylacosmylids. Hathliacynids usually have a longer snout than the other groups. The nasal bones extend past the eye sockets , often reaching the lacrimal bone . Except for thylacosmylids beyond Patagosmilus , sparassodonts feature an open eye socket, with more marginalized (though nonetheless prominent) postorbital processes which would otherwise form

2915-490: 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

2970-546: 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

3025-546: 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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