Smilodon

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Smilodon
Temporal range: Early
Ma
Mounted S. populator skeleton at Tellus Science Museum
Scientific classification Edit this classification
Domain: Eukaryota
Kingdom: Animalia
Phylum: Chordata
Class: Mammalia
Order: Carnivora
Suborder: Feliformia
Family: Felidae
Subfamily: Machairodontinae
Tribe: Smilodontini
Genus: Smilodon
Lund, 1842
Type species
Smilodon populator
Lund, 1842
Other species
  • S. fatalis Leidy, 1869
  • S. gracilis Cope, 1880
Synonyms
Genus synonymy
  • Munifelis Muñis, 1845
  • Trucifelis Leidy, 1868
  • Smilodontopsis Brown, 1908
  • Prosmilodon Rusconi, 1929
  • Smilodontidion Kraglievich, 1948
Species synonymy
  • S. populator:
    • Munifelis bonaerensis Muñis, 1845
    • Smilodon blainvillii Desmarest, 1860
    • Machaerodus bonaerensis Burmeister, 1867
    • Machaerodus necator Gervais, 1878
    • Smilodon ensenadensis Ameghino, 1888
    • Machaerodus ensenadensis Ameghino, 1889
    • Smilodon crucians Ameghino, 1904
    • Smilodon bonaerensis Ameghino, 1907
    • Smilodon neogaeus ensenadensis Boule & Thévenin, 1920
    • Smilodon (Prosmilodon) ensenadensis Rusconi, 1929
    • Smilodon neogaeus de Paula Couto, 1940
    • Smilodon necator de Paula Couto, 1940
    • Smilodon (Prosmilodon) ensenadensis ferox Kraglievich, 1947
    • Smilodon (Prosmilodon) ensenadensis minor Kraglievich, 1948
    • Smilodontidion riggii Kraglievich, 1948
    • Machaerodus neogaeus Pictet, 1953
    • Felis smilodon Desmarest, 1953
    • Smilodon populator populator de Paula Couto, 1955
  • S. fatalis:
    • Felis (Trucifelis) fatalis Leidy, 1868
    • Trucifelis fatalis Leidy, 1869
    • Machaerodus fatalis Lydekker, 1884
    • Drepanodon floridanus Leidy, 1889
    • Machaerodus floridanus Leidy, 1889
    • Uncia mercerii Cope, 1895
    • Smilodon floridanus Adams, 1896
    • Machaerodus (Smilodon) mercerii Cope, 1899
    • Smilodon californicus Bovard, 1907
    • Smilodontopsis troglodytes Brown, 1908
    • Smilodontopsis conardi Brown, 1908
    • Smilodontopsis mercerii Brown, 1908
    • Smilodon nebraskensis Matthew, 1918
    • Machaerodus mercerii Matthew, 1918
    • Smilodon (Trucifelis) californicus Merriam & Stock, 1932
    • Smilodon (Trucifelis) fatalis Merriam & Stock, 1932
    • Smilodon (Trucifelis) nebraskensis Merriam & Stock, 1932
    • Smilodon (Trucifelis) californicus brevipes Merriam & Stock, 1932
    • Smilodon trinitensis Slaughter, 1960
  • S. gracilis:
    • Machaerodus (Smilodon) gracilis Cope, 1899
    • Smilodon (Smilodontopsis) gracilis Merriam & Stock, 1932
    • Megantereon gracilis Broom & Schepers 1946
    • Ischyrosmilus gracilis Churcher, 1984
    • Smilodontopsis gracilis Berta, 1995

Smilodon is a

extinct subfamily Machairodontinae. It is one of the best known saber-toothed predators and prehistoric mammals. Although commonly known as the saber-toothed tiger, it was not closely related to the tiger or other modern cats. Smilodon lived in the Americas during the Pleistocene epoch (2.5 mya – 10,000 years ago). The genus was named in 1842 based on fossils from Brazil; the generic name means "scalpel" or "two-edged knife" combined with "tooth". Three species are recognized today: S. gracilis, S. fatalis, and S. populator. The two latter species were probably descended from S. gracilis, which itself probably evolved from Megantereon. The hundreds of specimens obtained from the La Brea Tar Pits in Los Angeles
constitute the largest collection of Smilodon fossils.

Overall, Smilodon was more robustly built than any

coat pattern of Smilodon is unknown, but it has been artistically restored
with plain or spotted patterns.

In North America, Smilodon

megafauna
disappeared, about 10,000 years ago. Its reliance on large animals has been proposed as the cause of its extinction. S. fatalis may have been impacted by habitat turnover and loss of prey it specialized on due to possible climatic plus anthropogenic impacts and other factors while the extinction of S. populator remains poorly understood.

Taxonomy

Zoological Museum, Copenhagen

During the 1830s, Danish

canine teeth and foot bones), Lund concluded the fossils instead belonged to a distinct genus of felids, though transitional to the hyenas. He stated it would have matched the largest modern predators in size, and was more robust than any modern cat. Lund originally wanted to name the new genus Hyaenodon, but realizing this had recently become preoccupied by another prehistoric predator, he instead named it Smilodon populator in 1842. He explained the Ancient Greek meaning of Smilodon as σμίλη (smilē), "scalpel" or "two-edged knife", and οδόντος (odóntos), "tooth". This has also been translated as "tooth shaped like double-edged knife". He explained the species name populator as "the destroyer", which has also been translated as "he who brings devastation". By 1846, Lund had acquired nearly every part of the skeleton (from different individuals), and more specimens were found in neighboring countries by other collectors in the following years.[1][2] Though some later authors used Lund's original species name neogaea instead of populator, it is now considered an invalid nomen nudum, as it was not accompanied with a proper description and no type specimens were designated.[3] Some South American specimens have been referred to other genera, subgenera, species, and subspecies, such as Smilodontidion riggii, Smilodon (Prosmilodon) ensenadensis, and S. bonaeriensis, but these are now thought to be junior synonyms of S. populator.[4]

molar and maxilla fragment of S. fatalis

Fossils of Smilodon were discovered in North America from the second half of the 19th century onwards.

new combination S. fatalis.[7] Most North American finds were scanty until excavations began in the La Brea Tar Pits in Los Angeles, where hundreds of individuals of S. fatalis have been found since 1875.[1] S. fatalis has junior synonyms such as S. mercerii, S. floridanus, and S. californicus.[4] American paleontologist Annalisa Berta considered the holotype of S. fatalis too incomplete to be an adequate type specimen, and the species has at times been proposed to be a junior synonym of S. populator.[3] Nordic paleontologists Björn Kurtén and Lars Werdelin supported the distinctness of the two species in an article published in 1990.[8] A 2018 article by the American paleontologist John P. Babiarz and colleagues concluded that S. californicus, represented by the specimens from the La Brea Tar Pits, was a distinct species from S. fatalis after all and that more research is needed to clarify the taxonomy of the lineage.[9]

In his 1880 article about extinct cats, Cope also named a third species of Smilodon, S. gracilis. The species was based on a partial canine, which had been obtained in the

state fossil of California.[1]

Evolution

Academy of Natural Sciences of Philadelphia

Long the most completely known

convergently evolved extremely long maxillary canines, as well as adaptations to the skull and skeleton related to their use. This includes members of Gorgonopsia, Thylacosmilidae, Machaeroidinae, Nimravidae, Barbourofelidae, and Machairodontinae.[1][13] Within the family Felidae (true cats), members of the subfamily Machairodontinae are referred to as saber-toothed cats, and this group is itself divided into three tribes: Metailurini (false saber-tooths); Homotherini (scimitar-toothed cats); and Smilodontini (dirk-toothed cats), to which Smilodon belongs.[4] Members of Smilodontini are defined by their long slender canines with fine to no serrations, whereas Homotherini are typified by shorter, broad, and more flattened canines, with coarser serrations.[14] Members of Metailurini were less specialized and had shorter, less flattened canines, and are not recognized as members of Machairodontinae by some researchers.[4]

The earliest felids are known from the Oligocene of Europe, such as Proailurus, and the earliest one with saber-tooth features is the Miocene genus Pseudaelurus.[4] The skull and mandible morphology of the earliest saber-toothed cats was similar to that of the modern clouded leopards (Neofelis). The lineage further adapted to the precision killing of large animals by developing elongated canine teeth and wider gapes, in the process sacrificing high bite force.[15] As their canines became longer, the bodies of the cats became more robust for immobilizing prey.[14] In derived smilodontins and homotherins, the lumbar region of the spine and the tail became shortened, as did the hind limbs.[4] Based on mitochondrial DNA sequences extracted from fossils, the lineages of Homotherium and Smilodon are estimated to have diverged about 18 Ma ago.[16]

The earliest species of Smilodon is S. gracilis, which existed from 2.5

million to 500,000 years ago (early Blancan to Irvingtonian ages) and was the successor in North America of Megantereon, from which it probably evolved. Megantereon itself had entered North America from Eurasia during the Pliocene, along with Homotherium. S. gracilis reached the northern regions of South America in the Early Pleistocene as part of the Great American Interchange.[17][14] S. fatalis existed 1.6 million–10,000 years ago (late Irvingtonian to Rancholabrean ages), and replaced S. gracilis in North America.[8] S. populator existed 1 million–10,000 years ago (Ensenadan to Lujanian ages); it occurred in the eastern parts of South America.[18]

Despite the colloquial name "saber-toothed tiger", Smilodon is not closely related to the modern tiger (which belongs in the subfamily Pantherinae), or any other extant felid.[19] A 1992 ancient DNA analysis suggested that Smilodon should be grouped with modern cats (subfamilies Felinae and Pantherinae).[20] A 2005 study found that Smilodon belonged to a separate lineage.[21] A study published in 2006 confirmed this, showing that the Machairodontinae diverged early from the ancestors of modern cats and were not closely related to any living species.[22] The following cladogram based on fossils and DNA analysis shows the placement of Smilodon among extinct and extant felids, after Rincón and colleagues, 2011:[17]

S. fatalis skeleton at National Museum of Natural History
S. populator statue in Tierpark Berlin
Felidae

Proailurus

Pseudaelurus

Pantherinae

Panthera (tigers, lions, jaguars, and leopards)

Felinae

Caracal

Leopardus (ocelot and relatives)

domestic cats and relatives)

Herpailurus (jaguarundi)

Miracinonyx

Puma (cougar)

Machairodontinae

Dinofelis

Paramachairodus

Megantereon

Smilodon gracilis

Smilodon populator

Smilodon fatalis

Description

Size of the three Smilodon species compared to a human

Skeleton

Smilodon was around the size of modern

sexually dimorphic. Some studies of S. fatalis fossils have found little difference between the sexes.[26][27] Conversely, a 2012 study found that, while fossils of S. fatalis show less variation in size among individuals than modern Panthera, they do appear to show the same difference between the sexes in some traits.[28]

S. gracilis was the smallest species, estimated at 55 to 100 kg (120 to 220 lb) in weight, about the size of a

fossil tracks from Argentina (for which the ichnotaxon name Smilodonichium has been proposed) have been attributed to S. populator, and measure 17.6 cm (6.9 in) by 19.2 cm (7.6 in).[33] This is larger than tracks of the Bengal tiger, to which the footprints have been compared.[34]

External features

Smilodon and other saber-toothed cats have been reconstructed with both plain-colored

feliforms), both of which are considered possible.[35] Studies of modern cat species have found that species that live in the open tend to have uniform coats while those that live in more vegetated habitats have more markings, with some exceptions.[36] Some coat features, such as the manes of male lions or the stripes of the tiger, are too unusual to predict from fossils.[35]

Traditionally, saber-toothed cats have been

extant phylogenetic bracketing (where the features of the closest extant relatives of a fossil taxon are used as reference) is the most reliable way of restoring the life-appearance of prehistoric animals, and the cat-like Smilodon restorations by Knight are therefore still accurate.[35] A 2022 study by Antón and colleagues concluded that the upper canines of Smilodon would have been visible when the mouth was closed, while those of Homotherium would have not, after examining fossils and extant big cats.[39]

Paleobiology

Diet

S. populator canine tooth; the tip points to the right

An apex predator, Smilodon primarily hunted large mammals. Isotopes preserved in the bones of S. fatalis in the La Brea Tar Pits reveal that ruminants like bison (Bison antiquus, which was much larger than the modern American bison) and camels (Camelops) were most commonly taken by the cats there.[40] Smilodon fatalis may have also occasionally preyed upon Glyptotherium, based on a skull from a juvenile Glyptotherium texanum recovered from Pleistocene deposits in Arizona that bear the distinctive elliptical puncture marks best matching those of Smilodon, indicating that the predator successfully bit into the skull through the glyptodont's armored cephalic shield.[41] In addition, isotopes preserved in the tooth enamel of S. gracilis specimens from Florida show that this species fed on the peccary Platygonus and the llama-like Hemiauchenia.[42] Stable carbon isotope measurements of S. gracilis remains in Florida varied significantly between different sites and show that the species was flexible in its feeding habits.[43] Isotopic studies of dire wolf (Aenocyon dirus) and American lion (Panthera atrox) bones show an overlap with S. fatalis in prey, which suggests that they were competitors.[40] More detailed isotope analysis however, indicates that Smilodon fatalis preferred forest-dwelling prey such as tapirs, deer and forest-dwelling bison as opposed to the dire wolves' preferences for prey inhabiting open areas such as grassland.[44] The availability of prey in the Rancho La Brea area was likely comparable to modern East Africa.[45]

Two S. populator stalking a Palaeolama group in Brazil

As Smilodon migrated to South America, its diet changed; bison were absent, the

osteoderms and a Lama scaphoid bone. In addition to this unambiguous evidence of bone consumption, the coprolites suggest that Smilodon had a more generalist diet than previously thought.[48] Examinations of dental microwear from La Brea further suggests that Smilodon consumed both flesh and bone.[49] Smilodon itself may have scavenged dire wolf kills.[50] It has been suggested that Smilodon was a pure scavenger that used its canines for display to assert dominance over carcasses, but this theory is not supported today as no modern terrestrial mammals are pure scavengers.[51]

Predatory behavior

Tracks from Argentina which may have been produced by Smilodon

The

supination capabilities in its paws, notably robust forelimbs compared to the hindlimbs, and was probably an ambush predator.[55]

The

cortical thickening to such an extent that they would have been able to sustain greater loading than those of extant big cats, or of the extinct American lion. The thickening of S. fatalis femurs was within the range of extant felids.[56] Its canines were fragile and could not have bitten into bone; due to the risk of breaking, these cats had to subdue and restrain their prey with their powerful forelimbs before they could use their canine teeth, and likely used quick slashing or stabbing bites rather than the slow, suffocating bites typically used by modern cats.[56] On rare occasions, as evidenced by fossils, Smilodon was willing to risk biting into bone with its canines. This may have been focused more towards competition such as other Smilodon or potential threats such as other carnivores than on prey.[54]

saber-toothed cat
(A) and reconstructions of neck bite in prey of different sizes (B, C)

Debate continues as to how Smilodon killed its prey. Traditionally, the most popular theory is that the cat delivered a deep stabbing bite or open-jawed stabbing thrust to the throat, killing the prey very quickly.[56][57] Another hypothesis suggests that Smilodon targeted the belly of its prey. This is disputed, as the curvature of their prey's belly would likely have prevented the cat from getting a good bite or stab.[58] In regard to how Smilodon delivered its bite, the "canine shear-bite" hypothesis has been favored, where flexion of the neck and rotation of the skull assisted in biting the prey, but this may be mechanically impossible. However, evidence from comparisons with Homotherium suggest that Smilodon was fully capable of and utilized the canine shear-bite as its primary means of killing prey, based on the fact that it had a thick skull and relatively little trabecular bone, while Homotherium had both more trabecular bone and a more lion-like clamping bite as its primary means of attacking prey. The discovery, made by Figueirido and Lautenschlager et al., published in 2018 suggests extremely different ecological adaptations in both machairodonts.[59] The mandibular flanges may have helped resist bending forces when the mandible was pulled against the hide of a prey animal.[60]

S. fatalis skull cast (left) and restoration by Mauricio Antón showing a wide gape

The protruding incisors were arranged in an arch, and were used to hold the prey still and stabilize it while the canine bite was delivered. The contact surface between the canine crown and the gum was enlarged, which helped stabilize the tooth and helped the cat sense when the tooth had penetrated to its maximum extent. Since saber-toothed cats generally had a relatively large infraorbital foramen (opening) in the skull, which housed nerves associated with the whiskers, it has been suggested the improved senses would have helped the cats' precision when biting outside their field of vision, and thereby prevent breakage of the canines. The blade-like carnassial teeth were used to cut skin to access the meat, and the reduced molars suggest that they were less adapted for crushing bones than modern cats.[51] As the food of modern cats enters the mouth through the side while cutting with the carnassials, not the front incisors between the canines, the animals do not need to gape widely, so the canines of Smilodon would likewise not have been a hindrance when feeding.[38] A study published in 2022 of how machairodonts fed revealed that wear patterns on the teeth of S. fatalis also suggest that it was capable of eating bone to a similar extent as lions. This and comparisons with bite marks left by the contemporary machairodont Xenosmilus suggest that Smilodon and its relatives could efficiently de-flesh a carcass of meat when feeding without being hindered by their long canines.[61]

Despite being more powerfully built than other large cats, Smilodon had a weaker bite. Modern big cats have more pronounced

trabecular bone for a stabbing canine-shear bite, whereas the latter had more trabecular bone and used a clamp and hold style more similar to lions. The two would therefore have held distinct ecological niches.[67]

Natural traps

, 1913

Many Smilodon specimens have been excavated from

asphalt seeps that acted as natural carnivore traps. Animals were accidentally trapped in the seeps and became bait for predators that came to scavenge, but these were then trapped themselves. The best-known of such traps are at La Brea in Los Angeles, which have produced over 166,000 Smilodon fatalis specimens[68] that form the largest collection in the world. The sediments of the pits there were accumulated 40,000 to 10,000 years ago, in the Late Pleistocene. Though the trapped animals were buried quickly, predators often managed to remove limb bones from them, but they were themselves often trapped and then scavenged by other predators; 90% of the excavated bones belonged to predators.[69]

The Talara Tar Seeps in Peru represent a similar scenario, and have also produced fossils of Smilodon. Unlike in La Brea, many of the bones were broken or show signs of weathering. This may have been because the layers were shallower, so the thrashing of trapped animals damaged the bones of previously trapped animals. Many of the carnivores at Talara were juveniles, possibly indicating that inexperienced and less fit animals had a greater chance of being trapped. Though Lund thought accumulations of Smilodon and herbivore fossils in the Lagoa Santa Caves were due to the cats using the caves as dens, these are probably the result of animals dying on the surface, and water currents subsequently dragging their bones to the floor of the cave, but some individuals may also have died after becoming lost in the caves.[69]

Social life

S. fatalis pair approaching a group of the ground sloth Paramylodon, one mired, at the La Brea Tar Pits, by Knight, 1921

Scientists debate whether Smilodon was

olfactory lures, the type of audio lure, and the length of the distress calls (the actual distress calls of the trapped prey animals would have lasted longer than the calls used in the study). The author of that study ponders what predators would have responded if the recordings were played in India, where the otherwise solitary tigers are known to aggregate around a single carcass.[71] The authors of the original study responded that though effects of the calls in the tar pits and the playback experiments would not be identical, this would not be enough to overturn their conclusions. In addition, they stated that weight and intelligence would not likely affect the results as lighter carnivores are far more numerous than heavy herbivores and the social (and seemingly intelligent) dire wolf is also found in the pits.[72]

Lion pride attacking an African buffalo in Tanzania; Smilodon may also have hunted in groups

Another argument for sociality is based on the healed injuries in several Smilodon fossils, which would suggest that the animals needed others to provide them food.[73][74] This argument has been questioned, as cats can recover quickly from even severe bone damage and an injured Smilodon could survive if it had access to water.[75] However, a Smilodon suffering hip dysplasia at a young age that survived to adulthood suggests that it could not have survived to adulthood without aid from a social group, as this individual was unable to hunt or defend its territory due to the severity of its congenital issue.[76] The brain of Smilodon was relatively small compared to other cat species. Some researchers have argued that Smilodon's brain would have been too small for it to have been a social animal.[77] An analysis of brain size in living big cats found no correlation between brain size and sociality.[78] Another argument against Smilodon being social is that being an ambush hunter in closed habitat would likely have made group-living unnecessary, as in most modern cats.[75] Yet it has also been proposed that being the largest predator in an environment comparable to the savanna of Africa, Smilodon may have had a social structure similar to modern lions, which possibly live in groups primarily to defend optimal territory from other lions (lions are the only social big cats today).[51]

Tip of an S. fatalis saber imbedded in the rib of another S. fatalis

Whether Smilodon was sexually dimorphic has implications for its reproductive behavior. Based on their conclusions that Smilodon fatalis had no sexual dimorphism, Van Valkenburgh and Sacco suggested in 2002 that, if the cats were social, they would likely have lived in

sexual display and competition, but a statistical study of the correlation between canine and body size in S. populator found no difference in scaling between body and canine size concluded it was more likely they evolved solely for a predatory function.[80]

A set of three associated skeletons of S. fatalis found in Ecuador and described in 2021 by Reynolds, Seymour, and Evans suggests that there was prolonged parental care in Smilodon. The two subadult individuals uncovered share a unique inherited trait in their dentaries, suggesting they were siblings; a rare instance of familial relationships being found in the fossil record. The subadult specimens are also hypothesized to have been male and female, respectively, while the adult skeletal remains found at the site are believed to have belonged to their mother. The subadults were estimated to have been around two years of age at the time of their deaths, but were still growing.[81] S. fatalis had proportionally larger hyoid bones than modern felid species and thus likely produced deeper vocalizations. While Smilodon had the same number of hyoid bones as the "roaring" cats, their shape was closer to that of "purring" species.[82]

Development

George C. Page Museum

Smilodon started developing its adult saber-teeth when the animal reached between 12 and 19 months of age, shortly after the completion of the eruption of the cat's

baby teeth. Both baby and adult canines would be present side by side in the mouth for an approximately 11-month period, and the muscles used in making the powerful bite were developed at about one-and-a-half years old as well, eight months earlier than in a modern lion. After Smilodon reached 23 to 30 months of age, the infant teeth were shed while the adult canines grew at an average growth rate of 7 mm (0.3 in) per month during a 12-month period. They reached their full size at around 3 years of age, later than modern species of big cats. Juvenile and adolescent Smilodon specimens are extremely rare at Rancho La Brea, where the study was performed, indicating that they remained hidden or at denning sites during hunts, and depended on parental care while their canines were developing.[83][84][85]

A 2017 study indicates that juveniles were born with a robust build similar to the adults. Comparison of the bones of juvenile S. fatalis specimens from La Brea with those of the contemporaneous American lion revealed that the two cats shared a similar growth curve. Felid forelimb development during ontogeny (changes during growth) has remained tightly constrained. The curve is similar to that for modern cats such as tigers and cougars, but shifts more towards the robust direction of the axes than is seen in modern felids.[86] Examinations by Reynolds, Seymour, and Evans (2021) suggest that Smilodon had a unique and fast growth rate similar to a tiger, but that there was a prolonged period of growth in the genus similar to what is seen in lions, and that the cubs were reliant on their parents until this growth period ended.[81]

Paleopathology

subchondral defects
in S. fatalis limb-joints (arrows)

Several Smilodon fossils show signs of ankylosing spondylitis, hyperostosis and trauma.[87] One study of 1,000 Smilodon skulls found that 36% of them had eroded parietal bones, which is where the largest jaw muscles attach. They also showed signs of microfractures, and the weakening and thinning of bones possibly caused by mechanical stress from the constant need to make stabbing motions with the canines.[88] Bony growths where the deltoid muscle inserted in the humerus is a common pathology for a La Brea specimen, which was probably due to repeated strain when Smilodon attempted to pull down prey with its forelimbs. Sternum injuries are also common, probably due to collision with prey.[89]

The frequency of trauma in S. fatalis specimens was 4.3%, compared to 2.8% in the dire wolf, which implies the ambush predatory behavior of the former led to greater risk of injury than the pursuit predatory behavior of the latter. Smilodon remains exhibit relatively more shoulder and

inbred, the researchers suggested this would have been the case for the prehistoric species as well as they approached extinction, but cautioned that more research was needed to determine if this was also the case in specimens from other parts of the Americas.[91]

Osteomyelitis in the left fourth metacarpal bone has been reported in a S. populator specimen dating back to Marine Isotope Stage 5. This pathology resulted in the machairodont individual becoming incapable of flexing its toe and would have severely diminished its ability to hunt prey.[92]

Distribution and habitat

Painting of animals around a lake
Environment of what is now White Sands National Park, with S. fatalis in the reeds in the right foreground

Smilodon lived during the

mammoth steppes in the north. The mosaic vegetation of woods, shrubs, and grasses in southwestern North America supported large herbivores such as horses, bison, antelope, deer, camels, mammoths, mastodons, and ground sloths. North America also supported other saber-toothed cats, such as Homotherium and Xenosmilus, as well as other large carnivores including dire wolves, short-faced bear (Arctodus simus) and the American lion.[14][69][96] Competition from such carnivores may have prevented North American S. fatalis from attaining the size of South America's S. populator. The similarity in size of S. fatalis and the American lion suggests niche overlap and direct competition between these species, and they appear to have fed on similarly sized prey.[97]

Animals that participated in the Great American Interchange, with North American migrants like S. populator (lower right) in blue

S. gracilis entered South America during the early to middle Pleistocene, where it probably gave rise to S. populator, which lived in the eastern part of the continent. S. fatalis also entered western South America in the late Pleistocene, and the two species were thought to be divided by the

thylacosmilids) had gone extinct by the Pliocene, and were replaced by North American carnivores such as canids, bears, and large cats.[14]

S. populator was very successful, while Homotherium never became widespread in South America. The extinction of the thylacosmilids has been attributed to competition with Smilodon, but this is probably incorrect, as they seem to have disappeared before the arrival of the large cats. The

Arctotherium angustidens, one of the largest carnivores ever, and could therefore assume the niche of mega-carnivore.[97] S. populator preferred large prey from open habitats such as grassland and plains, based on evidence gathered from isotope ratios that determined the animal's diet. In this way, the South American Smilodon species was probably similar to the modern lion. S. populator probably competed with the canid Protocyon there, but not with the jaguar, which fed primarily on smaller prey.[99][100] On the other hand, morphometry points to S. populator being best adapted for more closed environments.[101]

Extinction

, George C. Page Museum

Along with most of the New World Pleistocene megafauna, Smilodon became extinct by 10,000 years ago in the

Homo sapiens[103] (who entered the Americas around the time Smilodon disappeared), or a combination of several factors, all of which apply to the general Late Pleistocene extinction event, rather than specifically to the extinction of the saber-toothed cats.[104] One factor often cited here is the cooling in the Younger Dryas, which may have drastically reduced the habitable space for many species. In terms of human influence, there is evidence of a fire-induced regime change in Rancho la Brea that preceded the extirpation of megafauna in the area, with humans most likely responsible for the increase in fire intensity.[105]

Writers of the first half of the twentieth century theorized that the last saber-toothed cats, Smilodon and Homotherium, became extinct through competition with the faster and more generalized felids that replaced them. It was even proposed that the saber-toothed predators were inferior to modern cats, as the ever-growing canines were thought to inhibit their owners from feeding properly. Since then, however, it has been shown that the diet of machairodontines such as Smilodon and Homotherium was diverse. They do not seem to have been limited to giant animals as prey, as suggested before, but fed on whatever was available, including bovines, equines and camelids.[106][107] Additionally, non-machairodontine felids such as the American lion and Miracinonyx also became extinct during the Late Pleistocene, and saber-toothed and conical toothed felids had formerly coexisted for more than a million years.[108] The fact that saber-teeth evolved many times in unrelated lineages also attests to the success of this feature.[104]

Skeletal diagram of S. populator

The youngest direct radiocarbon date for S. fatalis differs from that of S. populator by thousands of years, the former just before the Younger Dryas cooling event and the latter by the early Holocene.[109] The latest S. fatalis specimen recovered from the Rancho La Brea tar pits has been dated to 13,025 years ago.[110] A specimen of S. fatalis from Iowa dates to 13,605–13,455 years Before Present (BP).[111] The latest Smilodon populator remains found in the cave of Cueva del Medio, near the town of Soria, northeast Última Esperanza Province, Magallanes Region in southernmost Chile have been dated to 10,935–11,209 years ago.[112] The most recent credible carbon-14 date for S. fatalis has been given as 11,130 BP.[113] However, such radiocarbon dates are likely uncalibrated, meaning that they were not adjusted from calendar years to regular years. As a result, the dates appear younger than they actually are. Therefore, the S. fatalis specimen from Rancho La Brea is the youngest-recorded of the species,[109] suggesting extinction before the Younger Dryas based on its last appearance in California as opposed to other regions where megafauna declined by the Younger Dryas.[105]

See also

References

  1. ^ a b c d e Antón 2013, pp. 3–26.
  2. ^ Lund, P. W. (1842). Blik paa Brasiliens Dyreverden för sidste Jordomvæltning (in Danish). Copenhagen: Det Kongelige Danske Videnskabernes Selskabs Naturvidenskabelige og Matematiske Afhandlinger. pp. 54–57.
  3. ^ a b c d e Berta, A. (1985). "The status of Smilodon in North and South America" (PDF). Contributions in Science, Natural History Museum of Los Angeles County. 370: 1–15. Archived from the original (PDF) on 28 May 2014.
  4. ^ a b c d e f g h i j Antón 2013, pp. 108–154.
  5. .
  6. ^ "Sabertooth". National Geographic. 21 September 2011. Retrieved 2021-10-13.
  7. ^
    JSTOR 2449549
    .
  8. ^ .
  9. .
  10. .
  11. ^ Berta, A. (1987). "The sabercat Smilodon gracilis from Florida and a discussion of its relationships (Mammalia, Felidae, Smilodontini)". Bulletin of the Florida State Museum. 31: 1–63.
  12. .
  13. .
  14. ^ a b c d e f g Antón 2013, pp. 65–76.
  15. PMID 18665225. Open access icon
  16. .
  17. ^ .
  18. .
  19. ^ "What Is a Sabertooth?". University of California Museum of Paleontology. December 2005. Retrieved 2012-06-12.
  20. PMID 1409696
    .
  21. .
  22. .
  23. ^ .
  24. ^ "What Is a Sabertooth?". University of California Museum of Paleontology. Retrieved 2013-04-08.
  25. S2CID 85353590
    .
  26. ^ .
  27. ^ .
  28. ^ .
  29. ^ .
  30. ^ "Saber-Toothed Cat, Smilodon fatalis". San Diego Zoo Global. January 2009. Archived from the original on 2013-02-03. Retrieved 2013-05-07.
  31. .
  32. .
  33. ^ "Hallazgo inédito en Miramar: huellas fosilizadas de un gran tigre dientes de sable". 0223.com.ar (in Spanish). 0223. May 26, 2016. Retrieved 28 May 2016.
  34. .
  35. ^ a b c d Antón 2013, pp. 157–176.
  36. PMID 20961899
    .
  37. ^ Miller, G. J. (1969). "A new hypothesis to explain the method of food ingestion used by Smilodon californicus Bovard". Tebiwa. 12: 9–19.
  38. ^ .
  39. .
  40. ^ (PDF) on November 11, 2011.
  41. ^ Antón 2013, pp. 203–204.
  42. – via University of Florida.
  43. . Retrieved 21 January 2024 – via Cambridge Core.
  44. .
  45. .
  46. .
  47. .
  48. .
  49. .
  50. .
  51. ^ a b c d e Antón 2013, pp. 176–216.
  52. S2CID 87481727
    .
  53. ^ "What Is a Sabertooth?". Berkeley.edu. Retrieved 1 June 2017.
  54. ^
    Anton, Mauricio
    (2013). Sabertooth.
  55. S2CID 134190731
    .
  56. ^
  57. .
  58. .
  59. .
  60. .
  61. ^ Hecht, J. (1 October 2007). "Sabre-tooth cat had a surprisingly delicate bite". New Scientist.
  62. PMID 15817436. Archived from the original (PDF) on 2013-08-25.{{cite journal}}: CS1 maint: numeric names: authors list (link
    )
  63. .
  64. ^ Martin, L. D. (1980). "Functional morphology and the evolution of cats". Transactions of the Nebraska Academy of Sciences. 8: 141–154.
  65. PMID 30293717
    .
  66. ^ Shaw, Christopher A.; Quinn, James P. (September 15, 2015). John M. Harris (ed.). "The Addition of Smilodon fatalis (Mammalia: Carnivora: Felidae) to the Biota of the Late Pleistocene Carpinteria Asphalt Deposits in California, with Ontogenetic and Ecologic Implications for the Species" (PDF). Science Series 42: Contributions in Science (A special volume entitled La Brea and Beyond: the Paleontology of Asphalt–Preserved Biotas in commemoration of the 100th anniversary of the Natural History Museum of Los Angeles County's excavations at Rancho La Brea). Natural History Museum of Los Angeles County: 91–95. Archived from the original (PDF) on December 25, 2016. Retrieved September 30, 2017.
  67. ^ a b c Antón 2013, pp. 30–33.
  68. PMID 18957359
    .
  69. .
  70. .
  71. ^ Heald, F. (1989). ""Injuries and diseases in Smilodon californicus Bovard, 1904, (Mammalia, Felidae) from Rancho La Brea, California". Journal of Vertebrate Paleontology. 9 (3): 24A.
  72. .
  73. ^ .
  74. .
  75. .
  76. .
  77. .
  78. .
  79. ^ .
  80. .
  81. ^ "Dagger-like canines of saber-toothed cats took years to grow". ScienceDaily. 2015-07-01. Archived from the original on 2015-07-02. Retrieved 2015-07-02.
  82. PMID 26132165. Open access icon
  83. .
  84. .
  85. .
  86. .
  87. ^ Antón 2013, p. 199.
  88. S2CID 8008808
    .
  89. .
  90. . Retrieved 5 February 2024 – via Elsevier Science Direct.
  91. .
  92. .
  93. .
  94. ^ DeSantis, L.R.G.; Schubert, B.W.; Schmitt-Linville, E.; Ungar, P.; Donohue, S.; Haupt, R.J. (September 15, 2015). John M. Harris (ed.). "Dental microwear textures of carnivorans from the La Brea Tar Pits, California and potential extinction implications" (PDF). Science Series 42: Contributions in Science (A special volume entitled La Brea and Beyond: the Paleontology of Asphalt–Preserved Biotas in commemoration of the 100th anniversary of the Natural History Museum of Los Angeles County's excavations at Rancho La Brea). Natural History Museum of Los Angeles County: 37–52. Archived from the original (PDF) on December 20, 2016. Retrieved February 6, 2017.
  95. ^ a b Sherani, S. (2016). A new specimen-dependent method of estimating felid body mass (No. e2327v2). PeerJ Preprints.
  96. .
  97. .
  98. ^ Hays, B. (2016-03-21). "Saber-toothed cats were the lions of prehistoric South America". UPI Science News. UPI. Retrieved 19 April 2016.
  99. ISSN 0094-8373
    . Retrieved 21 January 2024 – via Cambridge Core.
  100. .
  101. ^
  102. ^ a b Antón 2013, pp. 217–230.
  103. ^
    PMID 37590347
    .
  104. .
  105. .
  106. ^ Antón 2013, p. 223.
  107. ^ .
  108. .
  109. .
  110. .
  111. .

Bibliography