|S. fatalis skeleton at National Museum of Natural History, Washington, D.C.|
Smilodon is a genus of the extinct machairodont subfamily of the felids. It is one of the most famous prehistoric mammals and the best known saber-toothed cat. 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 individuals 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 extant cat, with particularly well-developed forelimbs and exceptionally long upper canine teeth. Its jaw had a bigger gape than that of modern cats, and its upper canines were slender and fragile, being adapted for precision killing. S. gracilis was the smallest species at 55 to 100 kg (120 to 220 lb) in weight. S. fatalis had a weight of 160 to 280 kg (350 to 620 lb) and height of 100 cm (39 in). Both of these species are mainly known from North America, but remains from South America have also been attributed to them. S. populator from South America was the largest species, at 220 to 436 kg (485 to 961 lb) in weight and 120 cm (47 in) in height, and was among the largest known felids. The coat pattern of Smilodon is unknown, but it has been artistically restored with plain or spotted patterns.
In North America, Smilodon hunted large herbivores such as bison and camels, and it remained successful even when encountering new prey species in South America. Smilodon is thought to have killed its prey by holding it still with its forelimbs and biting it, but it is unclear in what manner the bite itself was delivered. Scientists debate whether Smilodon had a social or a solitary lifestyle; analysis of modern predator behavior as well as of Smilodon's fossil remains could be construed to lend support to either view. Smilodon probably lived in closed habitats such as forests and bush, which would have provided cover for ambushing prey. Smilodon died out at the same time that most North and South American megafauna disappeared, about 10,000 years ago. Its reliance on large animals has been proposed as the cause of its extinction, along with climate change and competition with other species, but the exact cause is unknown.
During the 1830s, Danish naturalist Peter Wilhelm Lund and his assistants collected fossils in the calcareous caves near the small town of Lagoa Santa, Minas Gerais, Brazil. Among the thousands of fossils found, he recognized a few isolated cheek teeth as belonging to a hyena, which he named Hyaena neogaea in 1839. After more material was found (including canine teeth and foot bones), Lund concluded the fossils instead belonged to a distinct genus of felid, 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. Though some later authors used Lund's original species name neogaea instead of populator, it is now considered an invalid nomen nudum ("naked name"), as it was not accompanied with a proper description and no type specimens were designated. 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.
Fossils of Smilodon were discovered in North America from the second half of the 19th century onwards. In 1869, American paleontologist Joseph Leidy described a maxilla fragment with a molar, which had been discovered in a petroleum bed in Hardin County, Texas. He referred the specimen to the genus Felis (which was then used for most cats, extant as well as extinct) but found it distinct enough to be part of its own subgenus, as F. (Trucifelis) fatalis. The species name means "deadly". In an 1880 article about extinct American cats, American paleontologist Edward Drinker Cope pointed out that the F. fatalis molar was identical to that of Smilodon, and he proposed the new combination S. fatalis. 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. S. fatalis has junior synonyms such as S. mercerii, S. floridanus, and S. californicus. 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. Nordic paleontologists Björn Kurtén and Lars Werdelin supported the distinctness of the two species in an article published in 1990. 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.
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 Port Kennedy Cave near the Schuylkill River in Pennsylvania. Cope found the canine to be distinct from that of the other Smilodon species due to its smaller size and more compressed base. Its specific name refers to the species' lighter build. This species is known from fewer and less complete remains than the other members of the genus. S. gracilis has at times been considered part of genera such as Megantereon and Ischyrosmilus. S. populator, S. fatalis and S. gracilis are currently considered the only valid species of Smilodon, and features used to define most of their junior synonyms have been dismissed as variation between individuals of the same species (intraspecific variation). One of the most famous of prehistoric mammals, Smilodon has often been featured in popular media and is the state fossil of California.
Long the most completely known saber-toothed cat, Smilodon is still one of the best-known members of the group, to the point where the two concepts have been confused. The term "saber-tooth" refers to an ecomorph consisting of various groups of extinct predatory synapsids (mammals and close relatives), which 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. 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. 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. Members of Metailurini were less specialized and had shorter, less flattened canines, and are not recognized as members of Machairodontinae by some researchers.
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. 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. As their canines became longer, the bodies of the cats became more robust for immobilizing prey. In derived smilodontins and homotherins, the lumbar region of the spine and the tail became shortened, as did the hind limbs. Based on mitochondrial DNA sequences extracted from fossils, the lineages of Homotherium and Smilodon are estimated to have diverged about 18 Ma ago. 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. S. fatalis existed 1.6 million–10,000 years ago (late Irvingtonian to Rancholabrean ages), and replaced S. gracilis in North America. S. populator existed 1 million–10,000 years ago (Ensenadan to Lujanian ages); it occurred in the eastern parts of South America.
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. A 1992 ancient DNA analysis suggested that Smilodon should be grouped with modern cats (subfamilies Felinae and Pantherinae). A 2005 study found that Smilodon belonged to a separate lineage. 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. The following cladogram based on fossils and DNA analysis shows the placement of Smilodon among extinct and extant felids, after Rincón and colleagues, 2011:
Smilodon was around the size of modern big cats, but was more robustly built. It had a reduced lumbar region, high scapula, short tail, and broad limbs with relatively short feet. Smilodon is most famous for its relatively long canine teeth, which are the longest found in the saber-toothed cats, at about 28 cm (11 in) long in the largest species, S.populator. The canines were slender and had fine serrations on the front and back side. The skull was robustly proportioned and the muzzle was short and broad. The cheek bones (zygomata) were deep and widely arched, the sagittal crest was prominent, and the frontal region was slightly convex. The mandible had a flange on each side of the front. The upper incisors were large, sharp, and slanted forwards. There was a diastema (gap) between the incisors and molars of the mandible. The lower incisors were broad, recurved, and placed in a straight line across. The p3 premolar tooth of the mandible was present in most early specimens, but lost in later specimens; it was only present in 6% of the La Brea sample. There is some dispute over whether Smilodon was sexually dimorphic. Some studies of S. fatalis fossils have found little difference between the sexes. 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.
S. gracilis was the smallest species, estimated at 55 to 100 kg (120 to 220 lb) in weight, about the size of a jaguar. It was similar to its predecessor Megantereon of the same size, but its dentition and skull were more advanced, approaching S. fatalis. S. fatalis was intermediate in size between S. gracilis and S. populator. It ranged from 160 to 280 kg (350 to 620 lb). and reached a shoulder height of 100 cm (39 in) and body length of 175 cm (69 in). It was similar to a lion in dimensions, but was more robust and muscular, and therefore had a larger body mass. Its skull was also similar to that of Megantereon, though more massive and with larger canines. S. populator was among the largest known felids, with a body mass range of 220 to 400 kg (490 to 880 lb), and one estimate suggesting up to 470 kg (1,040 lb). A particularly large S. populator skull from Uruguay measuring 39 cm (15 in) in length indicates this individual may have weighed as much as 436 kg (961 lb). It stood at a shoulder height of 120 cm (47 in). Compared to S. fatalis, S. populator was more robust and had a more elongated and narrow skull with a straighter upper profile, higher positioned nasal bones, a more vertical occiput, more massive metapodials and slightly longer forelimbs relative to hindlimbs. Large 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). This is larger than tracks of the Bengal tiger, to which the footprints have been compared.
Traditionally, saber-toothed cats have been artistically restored with external features similar to those of extant felids, by artists such as Charles R. Knight in collaboration with various paleontologists in the early 20th century. In 1969, paleontologist G. J. Miller instead proposed that Smilodon would have looked very different from a typical cat and similar to a bulldog, with a lower lip line (to allow its mouth to open wide without tearing the facial tissues), a more retracted nose and lower-placed ears. Paleoartist Mauricio Antón and coauthors disputed this in 1998 and maintained that the facial features of Smilodon were overall not very different from those of other cats. Antón noted that modern animals like the hippopotamus are able to open their mouths extremely wide without tearing tissue due to a folded orbicularis oris muscle, and such a muscle arrangement exists in modern large felids. Antón stated that 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. 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.
Smilodon and other saber-toothed cats have been reconstructed with both plain-colored coats and with spotted patterns (which appears to be the ancestral condition for feliforms), both of which are considered possible. 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. Some coat features, such as the manes of male lions or the stripes of the tiger, are too unusual to predict from fossils.
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. 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. 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. 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. The availability of prey in the Rancho La Brea area was likely comparable to modern East Africa.
As Smilodon migrated to South America, its diet changed; bison were absent, the horses and proboscideans were different, and native ungulates such as toxodonts and litopterns were completely unfamiliar, yet S. populator thrived as well there as its relatives in North America. Isotopic analysis for Smilodon populator suggests that its main prey species included Toxodon platensis, Pachyarmatherium, Holmesina, species of the genus Panochthus, Palaeolama, Catonyx, Equus neogeus, and the crocodilian Caiman latirostris. This analysis of its diet also indicates that S. populator hunted both in open and forested habitats. The differences between the North and South American species may be due to the difference in prey between the two continents. Smilodon may have avoided eating bone and would have left enough food for scavengers. However, coprolites assigned to S. populator recovered from Argentina preserve Mylodon 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. Examinations of dental microwear from La Brea further suggests that Smilodon consumed both flesh and bone. Smilodon itself may have scavenged dire wolf kills. 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.
The brain of Smilodon had sulcal patterns similar to modern cats, which suggests an increased complexity of the regions that control the sense of hearing, sight, and coordination of the limbs. Felid saber-tooths in general had relatively small eyes that were not as forward-facing as those of modern cats, which have good binocular vision to help them move in trees. Smilodon was likely an ambush predator that concealed itself in dense vegetation, as its limb proportions were similar to modern forest-dwelling cats, and its short tail would not have helped it balance while running. Unlike its ancestor Megantereon, which was at least partially scansorial and therefore able to climb trees, Smilodon was probably completely terrestrial due to its greater weight and lack of climbing adaptations. Tracks from Argentina named Felipeda miramarensis in 2019 may have been produced by Smilodon. If correctly identified, the tracks indicate that the animal had fully retractible claws, plantigrade feet, lacked strong supination capabilities in its paws, notably robust forelimbs compared to the hindlimbs, and was probably an ambush predator.
The heel bone of Smilodon was fairly long, which suggests it was a good jumper. Its well-developed flexor and extensor muscles in its forearms probably enabled it to pull down, and securely hold down, large prey. Analysis of the cross-sections of S. fatalis humeri indicated that they were strengthened by 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. 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. 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.
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. 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. 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 2020 suggests extremely different ecological adaptations in both machairodonts. The mandibular flanges may have helped resist bending forces when the mandible was pulled against the hide of a prey animal.
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. 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. 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.
Despite being more powerfully built than other large cats, Smilodon had a weaker bite. Modern big cats have more pronounced zygomatic arches, while these were smaller in Smilodon, which restricted the thickness and therefore power of the temporalis muscles and thus reduced Smilodon's bite force. Analysis of its narrow jaws indicates that it could produce a bite only a third as strong as that of a lion (the bite force quotient measured for the lion is 112). There seems to be a general rule that the saber-toothed cats with the largest canines had proportionally weaker bites. Analyses of canine bending strength (the ability of the canine teeth to resist bending forces without breaking) and bite forces indicate that the saber-toothed cats' teeth were stronger relative to the bite force than those of modern big cats. In addition, Smilodon's gape could have reached over 110 degrees, while that of the modern lion reaches 65 degrees. This made the gape wide enough to allow Smilodon to grasp large prey despite the long canines. A 2018 study compared the killing behavior of Smilodon fatalis and Homotherium serum, and found that the former had a strong skull with little 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.
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 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.
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.
Scientists debate whether Smilodon was social. One study of African predators found that social predators like lions and spotted hyenas respond more to the distress calls of prey than solitary species. Since S. fatalis fossils are common at the La Brea Tar Pits, and were likely attracted by the distress calls of stuck prey, this could mean that this species was social as well. One critical study claims that the study neglects other factors, such as body mass (heavier animals are more likely to get stuck than lighter ones), intelligence (some social animals, like the American lion, may have avoided the tar because they were better able to recognize the hazard), lack of visual and 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. 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.
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. 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. 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. 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. An analysis of brain size in living big cats found no correlation between brain size and sociality. 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. 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).
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 monogamous pairs (along with offspring) with no intense competition among males for females. Likewise, Meachen-Samuels and Binder concluded in 2010 that aggression between males was less pronounced in S. fatalis than in the American lion. Christiansen and Harris found in 2012 that, as S. fatalis did exhibit some sexual dimorphism, there would have been evolutionary selection for competition between males. Some bones show evidence of having been bitten by other Smilodon, possibly the result of territorial battles, competition for breeding rights or over prey. Two S. populator skulls from Argentina show seemingly fatal, unhealed wounds which appear to have been caused by the canines of another Smilodon (though it cannot be ruled out they were caused by kicking prey). If caused by intraspecific fighting, it may also indicate that they had social behavior which could lead to death, as seen in some modern felines (as well as indicating that the canines could penetrate bone). It has been suggested that the exaggerated canines of saber-toothed cats evolved for 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.
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. The structure of the hyoid bones suggest that Smilodon could roar like modern big cats, which may have implications for their social life.
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.
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. 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.
Several Smilodon fossils show signs of ankylosing spondylitis, hyperostosis and trauma. 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. 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. 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 lumbar vertebrae injuries.
Distribution and habitat
Smilodon lived during the Pleistocene epoch (2.5 mya–10,000 years ago), and was perhaps the most recent of the saber-toothed cats. It probably lived in closed habitat such as forest or bush. Fossils of the genus have been found throughout the Americas. The northernmost remains of the genus are S. fatalis fossils from Alberta, Canada. The habitat of North America varied from subtropical forests and savannah in the south, to treeless 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. 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.
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 Andes mountains. However, in 2018, a skull of S. fatalis found in Uruguay east of the Andes was reported, which puts the idea that the two species were allopatric (geographically separated) into question. The American interchange resulted in a mix of native and invasive species sharing the prairies and woodlands in South America; North American herbivores included proboscideans, horses, camelids and deer, South American herbivores included toxodonts, litopterns, ground sloths, and glyptodonts. Native metatherian predators (including the saber-toothed thylacosmilids) had gone extinct by the Pliocene, and were replaced by North American carnivores such as canids, bears, and large cats.
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 phorusrhacid "terror birds" may have dominated the large predator niche in South America until Smilodon arrived. S. populator may have been able to reach larger size than S. fatalis due to a lack of competition in Pleistocene South America; S. populator arrived after the extinction of Arctotherium angustidens, one of the largest carnivores ever, and could therefore assume the niche of mega-carnivore. 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.
Along with most of the Pleistocene megafauna, Smilodon became extinct 10,000 years ago in the Quaternary extinction event. Its extinction has been linked to the decline and extinction of large herbivores, which were replaced by smaller and more agile ones like deer. Hence, Smilodon could have been too specialized at hunting large prey and may have been unable to adapt. A 2012 study of Smilodon tooth wear found no evidence that they were limited by food resources. Other explanations include climate change and competition with Homo sapiens (who entered the Americas around the time Smilodon disappeared), or a combination of several factors, all of which apply to the general Pleistocene extinction event, rather than specifically to the extinction of the saber-toothed cats.
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. Yet fast felids, such as the American lion and the American cheetah (Miracinonyx), also became extinct during the Late Pleistocene. The fact that saber-teeth evolved many times in unrelated lineages also attests to the success of this feature.
The latest Smilodon fatalis specimen recovered from the Rancho La Brea tar pits has been dated to 13,025 years ago. 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. The most recent carbon-14 date for S. fatalis reported was 10,200 years BP for remains from the First American Cave in 1971; however, the most recent "credible" date has been given as 11,130 BP.
- List of largest carnivorans
- List of largest prehistoric carnivorans
- Quaternary extinction event
- Antón 2013, pp. 3–26.
- 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.
- 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.
- Antón 2013, pp. 108–154.
- Leidy, J. (1869). "The extinct mammalian fauna of Dakota and Nebraska: Including an account of some allied forms from other localities, together with a synopsis of the mammalian remains of North America". Journal of the Academy of Natural Sciences of Philadelphia. 7: 366–367. doi:10.5962/bhl.title.20910.
- "Sabertooth". National Geographic. 21 September 2011. Retrieved 2021-10-13.
- Cope, E. D. (December 1880). "On the extinct cats of America". The American Naturalist. 14 (12): 833–858. doi:10.1086/272672. JSTOR 2449549.
- Kurtén, B.; Werdelin, L. (1990). "Relationships between North and South American Smilodon". Journal of Vertebrate Paleontology. 10 (2): 158–169. doi:10.1080/02724634.1990.10011804. JSTOR 4523312.
- Werdelin, L.; McDonald, H. G.; Shaw, C. A. (2018). Smilodon: The Iconic Sabertooth (Smilodon from South Carolina: Implications for the taxonomy of the genus ed.). Baltimore: Johns Hopkins University Press. pp. 76–95. ISBN 978-1-4214-2557-3.
- Kurtén, B.; Anderson, E. (1980). Pleistocene Mammals of North America. New York: Columbia University Press. pp. 186–188. ISBN 978-0-231-03733-4.
- 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.
- Churcher, C. S. (1984). The status of Smilodontopsis (Brown, 1908) and Ischyrosmilus (Merriam, 1918): a taxonomic review of two genera of sabretooth cats (Felidae, Machairodontinae). Royal Ontario Museum Life Sciences Contributions. Vol. 140. Royal Ontario Museum. pp. 14–34. doi:10.5962/bhl.title.52222. ISBN 978-0-88854-305-9.
- Meehan, T.; Martin, L. D. J. (2003). "Extinction and re-evolution of similar adaptive types (ecomorphs) in Cenozoic North American ungulates and carnivores reflect van der Hammen's cycles". Die Naturwissenschaften. 90 (3): 131–135. Bibcode:2003NW.....90..131M. doi:10.1007/s00114-002-0392-1. PMID 12649755. S2CID 21117744.
- Antón 2013, pp. 65–76.
- Christiansen, P. (2008). "Evolution of skull and mandible shape in cats (Carnivora: Felidae)". PLOS ONE. 3 (7): e2807. Bibcode:2008PLoSO...3.2807C. doi:10.1371/journal.pone.0002807. PMC 2475670. PMID 18665225.
- Paijmans, J. L. A.; Barnett, R.; Gilbert, M. T. P.; Zepeda-Mendoza, M. L.; Reumer, J. W. F.; de Vos, J.; Zazula, G.; Nagel, D.; Baryshnikov, G. F.; Leonard, J. A.; Rohland, N.; Westbury, M. V.; Barlow, A.; Hofreiter, M. (2017-10-19). "Evolutionary History of Saber-Toothed Cats Based on Ancient Mitogenomics". Current Biology. 27 (21): 3330–3336.e5. doi:10.1016/j.cub.2017.09.033. PMID 29056454.
- Rincón, A.; Prevosti, F.; Parra, G. (2011). "New saber-toothed cat records (Felidae: Machairodontinae) for the Pleistocene of Venezuela, and the Great American Biotic Interchange". Journal of Vertebrate Paleontology. 31 (2): 468–478. doi:10.1080/02724634.2011.550366. JSTOR 25835839. S2CID 129693331.
- de Castro, Mariela Cordeiro; Langer, Max Cardoso (2008). "New postcranial remains of Smilodon populator Lund, 1842 from South-Central Brazil". Revista Brasileira de Paleontologia. 11 (3): 199–206. doi:10.4072/rbp.2008.3.06.
- "What Is a Sabertooth?". University of California Museum of Paleontology. December 2005. Retrieved 2012-06-12.
- Janczewski, D. N.; Yuhki, N.; Gilbert, D. A.; Jefferson, G. T.; O'Brien, S. J. (1992). "Molecular phylogenetic inference from saber-toothed cat fossils of Rancho La Brea". Proceedings of the National Academy of Sciences. 89 (20): 9769–9773. Bibcode:1992PNAS...89.9769J. doi:10.1073/pnas.89.20.9769. PMC 50214. PMID 1409696.
- Barnett, R.; Barnes, I.; Phillips, M. J.; Martin, L. D.; Harington, C. R.; Leonard, J. A.; Cooper, A. (2005). "Evolution of the extinct sabretooths and the American cheetah-like cat". Current Biology. 15 (15): R589–R590. doi:10.1016/j.cub.2005.07.052. PMID 16085477. S2CID 17665121.
- van den Hoek Ostende, L. W.; Morlo, M.; Nagel, D. (2006). "Majestic killers: the sabre-toothed cats (Fossils explained 52)". Geology Today. 22 (4): 150–157. doi:10.1111/j.1365-2451.2006.00572.x. S2CID 128960196.
- Turner, A.; Antón, M. (1997). The Big Cats and Their Fossil Relatives: An Illustrated Guide to Their Evolution and Natural History. Columbia University Press. pp. 57–58, 67–68. ISBN 978-0-231-10229-2. OCLC 34283113.
- "What Is a Sabertooth?". University of California Museum of Paleontology. Retrieved 2013-04-08.
- Slater, G. J.; Valkenburgh, B. V. (2008). "Long in the tooth: evolution of sabertooth cat cranial shape". Paleobiology. 34 (3): 403–419. doi:10.1666/07061.1. ISSN 0094-8373. S2CID 85353590.
- Van Valkenburgh, B.; Sacco, T. (2002). "Sexual dimorphism, social behavior and intrasexual competition in large Pleistocene carnivorans". Journal of Vertebrate Paleontology. 22 (1): 164–169. doi:10.1671/0272-4634(2002)022[0164:sdsbai]2.0.co;2. JSTOR 4524203. S2CID 86156959.
- Meachen-Samuels, J.; Binder, W. (2010). "Sexual dimorphism and ontogenetic growth in the American lion and sabertoothed cat from Rancho La Brea". Journal of Zoology. 280 (3): 271–279. doi:10.1111/j.1469-7998.2009.00659.x.
- Christiansen, Per; Harris, John M. (2012). "Variation in Craniomandibular Morphology and Sexual Dimorphism in Pantherines and the Sabercat Smilodon fatalis". PLOS ONE. 7 (10): e48352. Bibcode:2012PLoSO...748352C. doi:10.1371/journal.pone.0048352. PMC 3482211. PMID 23110232.
- Christiansen, Per; Harris, John M. (2005). "Body size of Smilodon (Mammalia: Felidae)". Journal of Morphology. 266 (3): 369–84. doi:10.1002/jmor.10384. PMID 16235255. S2CID 27233870.
- "Saber-Toothed Cat, Smilodon fatalis". San Diego Zoo Global. January 2009. Archived from the original on 2013-02-03. Retrieved 2013-05-07.
- Sorkin, B. (2008). "A biomechanical constraint on body mass in terrestrial mammalian predators". Lethaia. 41 (4): 333–347. doi:10.1111/j.1502-3931.2007.00091.x.
- Manzuetti, A.; Perea, D.; Jones, W.; Ubilla, M.; Rinderknecht, A. (2020). "An extremely large saber-tooth cat skull from Uruguay (late Pleistocene–early Holocene, Dolores Formation): body size and paleobiological implications". Alcheringa: An Australasian Journal of Palaeontology. 44 (2): 332–339. doi:10.1080/03115518.2019.1701080. S2CID 216505747.
- "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.
- Perkins, Sid (June 10, 2016). "First fossil footprints of saber-toothed cats are bigger than Bengal tiger paws". Science. doi:10.1126/science.aag0602.
- Antón 2013, pp. 157–176.
- Miller, G. J. (1969). "A new hypothesis to explain the method of food ingestion used by Smilodon californicus Bovard". Tebiwa. 12: 9–19.
- Antón, M.; García-Perea, R.; Turner, A. (1998). "Reconstructed facial appearance of the sabretoothed felid Smilodon". Zoological Journal of the Linnean Society. 124 (4): 369–386. doi:10.1111/j.1096-3642.1998.tb00582.x.
- Antón, Mauricio; Siliceo, Gema; Pastor, Juan F.; Salesa, Manuel J. (2022). "Concealed weapons: A revised reconstruction of the facial anatomy and life appearance of the sabre-toothed cat Homotherium latidens (Felidae, Machairodontinae)". Quaternary Science Reviews. 284: 107471. Bibcode:2022QSRv..28407471A. doi:10.1016/j.quascirev.2022.107471. S2CID 248168629.
- Allen, W. L.; Cuthill, I. C.; Scott-Samuel, N. E.; Baddeley, R. (2010). "Why the leopard got its spots: relating pattern development to ecology in felids". Proceedings of the Royal Society B. 278 (1710): 1373–1380. doi:10.1098/rspb.2010.1734. PMC 3061134. PMID 20961899.
- Coltrain, J. B.; Harris, J. M.; Cerling, T. E.; Ehleringer, J. R.; Dearing, M.-D.; Ward, J.; Allen, J. (2004). "Rancho La Brea stable isotope biogeochemistry and its implications for the palaeoecology of late Pleistocene, coastal southern California" (PDF). Palaeogeography, Palaeoclimatology, Palaeoecology. 205 (3–4): 199–219. Bibcode:2004PPP...205..199C. doi:10.1016/j.palaeo.2003.12.008. Archived from the original (PDF) on November 11, 2011.
- Feranec, R. S. (2005). "Growth rate and duration of growth in the adult canine of S. gracilis and inferences on diet through stable isotope analysis" (PDF). Bulletin of the Florida Museum of Natural History. 45 (4): 369–377 – via University of Florida.
- DeSantis, Larisa R. G.; Crites, Jonathan M.; Feranec, Robert S.; Fox-Dobbs, Kena; Farrell, Aisling B.; Harris, John M.; Takeuchi, Gary T.; Cerling, Thure E. (2019). "Causes and Consequences of Pleistocene Megafaunal Extinctions as Revealed from Rancho La Brea Mammals". Current Biology. 29 (15): 2488–2495. doi:10.1016/j.cub.2019.06.059. PMID 31386836.
- Vanvalkenburgh, B.; Hertel, F. (1993). "Tough Times at La Brea: Tooth Breakage in Large Carnivores of the Late Pleistocene". Science. 261 (5120): 456–459. Bibcode:1993Sci...261..456V. doi:10.1126/science.261.5120.456. PMID 17770024. S2CID 39657617.
- Dantas, Mário André Trindade; Cherkinsky, Alexander; Lessa, Carlos Micael Bonfim; Santos, Luciano Vilaboim; Cozzuol, Mario Alberto; Omena, Érica Cavalcante; Silva, Jorge Luiz Lopes; Sial, Alcides Nóbrega; Bocherens, Hervé (2020-07-14). "Isotopic paleoecology (δ13C, δ18O) of a late Pleistocene vertebrate community from the Brazilian Intertropical Region". Revista Brasileira de Paleontologia. 23 (2): 138–152. doi:10.4072/rbp.2020.2.05. ISSN 2236-1715.
- Van Valkenburgh, B.; Teaford, M. F.; Walker, A. (1990). "Molar microwear and diet in large carnivores: inferences concerning diet in the sabretooth cat, Smilodon fatalis". Journal of Zoology. 222 (2): 319–340. doi:10.1111/j.1469-7998.1990.tb05680.x.
- Moreno Rodríguez, Ana P.; Chimento, Nicolás R.; Agnolín, Federico L.; Jofré, Guillermo; Gentil, Adriel (2022-07-31). "A Possible Smilodon (Mammalia, Felidae) Coprolite from the Pleistocene of Argentina". PALAIOS. 37 (7): 402–410. Bibcode:2022Palai..37..402M. doi:10.2110/palo.2021.056. ISSN 1938-5323. S2CID 251078622.
- DeSantis, Larisa R.G.; Shaw, Christopher A. (2018). "Sabertooth Cats with Toothaches: Impacts of Dental Injuries on Feeding Behavior in Late Pleistocene Smilodon Fatalis (Mammalia, Felidae) from Rancho la Brea (Los Angeles, California)". Geological Society of America Abstracts with Programs. 50 (6): 322567. doi:10.1130/abs/2018AM-322567.
- Van Valkenburgh, B. (1991). "Iterative evolution of hypercarnivory in canids (Mammalia: Carnivora): evolutionary interactions among sympatric predators". Paleobiology. 17 (4): 340–362. doi:10.1017/S0094837300010691. JSTOR 2400749. S2CID 251052044.
- Antón 2013, pp. 176–216.
- Gonyea, W. J. (1976). "Behavioral implications of saber-toothed felid morphology". Paleobiology. 2 (4): 332–342. doi:10.1017/S0094837300004966. JSTOR 2400172. S2CID 87481727.
- "What Is a Sabertooth?". Berkeley.edu. Retrieved 1 June 2017.
- Anton, Mauricio (2013). Sabertooth.
- Agnolin, F. L.; Chimento, N. R.; Campo, D. H.; Magnussen, M.; Boh, D.; De Cianni, F. (2019). "Large Carnivore Footprints from the Late Pleistocene of Argentina". Ichnos. 26 (2): 119–126. doi:10.1080/10420940.2018.1479962. S2CID 134190731.
- Meachen-Samuels, J. A.; Van Valkenburgh, B. (2010). "Radiographs reveal exceptional forelimb strength in the sabertooth cat, Smilodon fatalis". PLOS ONE. 5 (7): e11412. Bibcode:2010PLoSO...511412M. doi:10.1371/journal.pone.0011412. ISSN 1932-6203. PMC 2896400. PMID 20625398.
- McHenry, C. R.; Wroe, S.; Clausen, P. D.; Moreno, K.; Cunningham, E. (2007). "Supermodeled sabercat, predatory behavior in Smilodon fatalis revealed by high-resolution 3D computer simulation". PNAS. 104 (41): 16010–16015. Bibcode:2007PNAS..10416010M. doi:10.1073/pnas.0706086104. PMC 2042153. PMID 17911253.
- Anyonge, W. (1996). "Microwear on canines and killing behavior in large carnivores: saber function in Smilodon fatalis". Journal of Mammalogy. 77 (4): 1059–1067. doi:10.2307/1382786. JSTOR 1382786.
- Figueirido, B.; Lautenschlager, S.; Pérez-Ramos, A.; Van Valkenburgh, B. (2018). "Distinct Predatory Behaviors in Scimitar- and Dirk-Toothed Sabertooth Cats". Current Biology. 28 (20): 3260–3266.e3. doi:10.1016/j.cub.2018.08.012. PMID 30293717.
- Macchiarelli, R.; Brown, J. G. (2014). "Jaw function in Smilodon fatalis: a reevaluation of the canine shear-bite and a proposal for a new forelimb-powered class 1 lever model". PLOS ONE. 9 (10): e107456. Bibcode:2014PLoSO...9j7456B. doi:10.1371/journal.pone.0107456. ISSN 1932-6203. PMC 4182664. PMID 25272032.
- Domínguez-Rodrigo, Manuel; Egeland, Charles P.; Cobo-Sánchez, Lucía; Baquedano, Enrique; Hulbert, Richard C. (2022). "Sabertooth carcass consumption behavior and the dynamics of Pleistocene large carnivoran guilds". Scientific Reports. 12 (1): 6045. Bibcode:2022NatSR..12.6045D. doi:10.1038/s41598-022-09480-7. PMC 9061710. PMID 35501323.
- Hecht, J. (1 October 2007). "Sabre-tooth cat had a surprisingly delicate bite". New Scientist.
- Wroe, S.; McHenry2, C.; Thomason, J. (2004). "Bite club: comparative bite force in big biting mammals and the prediction of predatory behaviour in fossil taxa" (PDF). Proceedings of the Royal Society. 272 (1563): 619–25. doi:10.1098/rspb.2004.2986. PMC 1564077. PMID 15817436. Archived from the original (PDF) on 2013-08-25.
- Christiansen, P. (2007). "Comparative bite forces and canine bending strength in feline and sabretooth felids: implications for predatory ecology". Zoological Journal of the Linnean Society. 151 (2): 423–437. doi:10.1111/j.1096-3642.2007.00321.x.
- Andersson, K.; Norman, D.; Werdelin, L. (2011). "Sabretoothed carnivores and the killing of large prey". PLOS ONE. 6 (10): e24971. Bibcode:2011PLoSO...624971A. doi:10.1371/journal.pone.0024971. PMC 3198467. PMID 22039403.
- Martin, L. D. (1980). "Functional morphology and the evolution of cats". Transactions of the Nebraska Academy of Sciences. 8: 141–154.
- Figueirido, B.; Lautenschlager, S.; Pérez-Ramos, A.; Van Valkenburgh, B. (2018). "Distinct Predatory Behaviors in Scimitar- and Dirk-Toothed Sabertooth Cats". Current Biology. 28 (20): 3260–3266.e3. doi:10.1016/j.cub.2018.08.012. PMID 30293717.
- 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. Natural History Museum of Los Angeles County (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): 91–95. Archived from the original (PDF) on December 25, 2016. Retrieved September 30, 2017.
- Antón 2013, pp. 30–33.
- Carbone, C.; Maddox, T.; Funston, P. J.; Mills, M. G. L.; Grether, G. F.; Van Valkenburgh, B. (2009). "Parallels between playbacks and Pleistocene tar seeps suggest sociality in an extinct sabretooth cat, Smilodon". Biology Letters. 5 (1): 81–85. doi:10.1098/rsbl.2008.0526. PMC 2657756. PMID 18957359.
- Kiffner, C. (2009). "Coincidence or evidence: was the sabretooth cat Smilodon social?". Biology Letters. 5 (4): 561–562. doi:10.1098/rsbl.2009.0008. PMC 2781900. PMID 19443504.
- Van Valkenburgh, B.; Maddox, T.; Funston, P. J.; Mills, M. G. L.; Grether, G. F.; Carbone, C. (2009). "Sociality in Rancho La Brea Smilodon: arguments favour 'evidence' over 'coincidence'". Biology Letters. 5 (4): 563–564. doi:10.1098/rsbl.2009.0261. PMC 2781931.
- 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.
- Balisi, M. A.; Sharma, A. K.; Howard, C. M.; Shaw, C. A.; Klapper, R.; Lindsey, Emily L. (2020). "Computed tomography reveals hip dysplasia in Smilodon: Implications for social behavior in an extinct Pleistocene predator". bioRxiv 10.1101/2020.01.07.897348.
- McCall, S.; Naples, V.; Martin, L. (2003). "Assessing behavior in extinct animals: was Smilodon social?". Brain, Behavior and Evolution. 61 (3): 159–164. doi:10.1159/000069752. PMID 12697957. S2CID 2756104.
- Balisi, Mairin A.; Sharma, Abhinav K.; Howard, Carrie M.; Shaw, Christopher A.; Klapper, Robert; Lindsey, Emily L. (2021). "Computed tomography reveals hip dysplasia in the extinct Pleistocene saber-tooth cat Smilodon". bioRxiv. 11 (1): 21271. doi:10.1101/2020.01.07.897348. PMC 8553773. PMID 34711910. S2CID 235663241.
- Radinsky, L. B. (1975). "Evolution of the felid brain". Brain, Behavior and Evolution. 11 (3–4): 214–254. doi:10.1159/000123636. PMID 1181005.
- Yamaguchi, N.; Kitchener, A. C.; Gilissen, E.; MacDonald, D. W. (2009). "Brain size of the lion (Panthera leo) and the tiger (P. tigris): implications for intrageneric phylogeny, intraspecific differences and the effects of captivity". Biological Journal of the Linnean Society. 98 (1): 85–93. doi:10.1111/j.1095-8312.2009.01249.x.
- Chimento, N. R.; Agnolin, F. L.; Soibelzon, L.; Ochoa, J. G.; Buide, V. (2019). "Evidence of intraspecific agonistic interactions in Smilodon populator (Carnivora, Felidae)". Comptes Rendus Palevol. 18 (4): 449–454. doi:10.1016/j.crpv.2019.02.006.
- O’Brien, D. M (2019). "Static scaling and the evolution of extreme canine size in a saber-toothed cat (Smilodon fatalis)". Integrative and Comparative Biology. 59 (5): 1303–1311. doi:10.1093/icb/icz054. PMID 31120517.
- Reynolds, Ashley R.; Seymour, Kevin L.; Evans, David C. (January 7, 2021). "Smilodon fatalis siblings reveal life history in a saber-toothed cat". iScience. 24 (1): 101916. Bibcode:2021iSci...24j1916R. doi:10.1016/j.isci.2020.101916. PMC 7835254. PMID 33532710.
- Hearld, F.; Shaw, C. (1991). "Sabertooth Cats". In Seidensticker, J.; Lumpkin, S. (eds.). The Great Cats. Rodale Pr. p. 26. ISBN 978-1-875137-90-9.
- Pickrell, J. (2018). "Saber-Toothed Cats May Have Roared Like Lions". Scientific American. Retrieved 29 October 2018.
- "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.
- Mihlbachler, M. C.; Wysocki, M. A.; Feranec, R. S.; Tseng, Z. J.; Bjornsson, C. S. (2015-07-01). "Using a novel absolute ontogenetic age determination technique to calculate the timing of tooth eruption in the saber-toothed cat, Smilodon fatalis". PLOS ONE. 10 (7): e0129847. Bibcode:2015PLoSO..1029847W. doi:10.1371/journal.pone.0129847. PMC 4489498. PMID 26132165.
- Feranec, R. C. (2004). "Isotopic evidence of saber-tooth development, growth rate, and diet from the adult canine of Smilodon fatalis from Rancho La Brea". Palaeogeography, Palaeoclimatology, Palaeoecology. 206 (3–4): 303–310. Bibcode:2004PPP...206..303F. doi:10.1016/j.palaeo.2004.01.009.
- Long, K.; Prothero, D.; Madan, M.; Syverson, V. J. P.; Smith, T. (2017). "Did saber-tooth kittens grow up musclebound? A study of postnatal limb bone allometry in felids from the Pleistocene of Rancho La Brea". PLOS ONE. 12 (9): e0183175. Bibcode:2017PLoSO..1283175L. doi:10.1371/journal.pone.0183175. PMC 5617143. PMID 28953899.
- Bjorkengren, A. G.; Sartoris, D. J.; Shermis, S.; Resnick, D. (1987). "Patterns of paravertebral ossification in the prehistoric saber-toothed cat". American Journal of Roentgenology. 148 (4): 779–782. doi:10.2214/ajr.148.4.779. PMID 3103404.
- Duckler, G. L. (1997). "Parietal depressions in skulls of the extinct saber-toothed felid Smilodon fatalis: evidence of mechanical strain". Journal of Vertebrate Paleontology. 17 (3): 600–609. doi:10.1080/02724634.1997.10011006.
- Brown, C.; Balisi, M.; Shaw, C. A.; Van Valkenburgh, B. (2017). "Skeletal trauma reflects hunting behaviour in extinct sabre-tooth cats and dire wolves". Nature Ecology & Evolution. 1 (5): 0131. doi:10.1038/s41559-017-0131. PMID 28812696. S2CID 8008808.
- Meloro, C.; Elton, S.; Louys, J.; Bishop, L. C.; Ditchfield, P. (2013). "Cats in the forest: predicting habitat adaptations from humerus morphometry in extant and fossil Felidae (Carnivora)" (PDF). Paleobiology. 39 (3): 323–344. doi:10.1666/12001. S2CID 83957027.
- Reynolds, A. R.; Seymour, K. L.; Evans, D. C. (2019). "Late Pleistocene records of felids from Medicine Hat, Alberta, including the first Canadian record of the sabre-toothed cat Smilodon fatalis". Canadian Journal of Earth Sciences. 56 (10): 1052–1060. Bibcode:2019CaJES..56.1052R. doi:10.1139/cjes-2018-0272. hdl:1807/96725. S2CID 134586651.
- 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. Natural History Museum of Los Angeles County (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): 37–52. Archived from the original (PDF) on December 20, 2016. Retrieved February 6, 2017.
- Sherani, S. (2016). A new specimen-dependent method of estimating felid body mass (No. e2327v2). PeerJ Preprints.
- Manzuetti, A.; Perea, D.; Ubilla, M.; Rinderknecht, A. (2018). "First record of Smilodon fatalis Leidy, 1868 (Felidae, Machairodontinae) in the extra-Andean region of South America (late Pleistocene, Sopas Formation), Uruguay: Taxonomic and paleobiogeographic implications". Quaternary Science Reviews. 180: 57–62. Bibcode:2018QSRv..180....1M. doi:10.1016/j.quascirev.2017.11.024.
- Bocherens, H.; Cotte, M.; Bonini, R.; Scian, D.; Straccia, P.; Soibelzon, L.; Prevosti, F. J. (2016-04-24). "Paleobiology of sabretooth cat Smilodon population in the Pampean Region (Buenos Aires Province, Argentina) around the Last Glacial Maximum: Insights from carbon and nitrogen stable isotopes in bone collagen". Palaeogeography, Palaeoclimatology, Palaeoecology. 449: 463–474. Bibcode:2016PPP...449..463B. doi:10.1016/j.palaeo.2016.02.017.
- Hays, B. (2016-03-21). "Saber-toothed cats were the lions of prehistoric South America". UPI Science News. UPI. Retrieved 2016-04-19.
- DeSantis, L. R. G.; Schubert, B. W.; Scott, J. R.; Ungar, P. S. (2012). "Implications of diet for the extinction of saber-toothed cats and American lions". PLOS ONE. 7 (12): e52453. Bibcode:2012PLoSO...752453D. doi:10.1371/journal.pone.0052453. PMC 3530457. PMID 23300674.
- Antón 2013, pp. 217–230.
- O'Keefe, F.R.; Fet, E.V.; Harris, J.M. (2009). "Compilation, calibration, and synthesis of faunal and floral radiocarbon dates, Rancho La Brea, California". Contributions in Science. 518: 1–16. doi:10.5962/p.226783. S2CID 128107590.
- Prieto, Alfredo; Labarca, Rafael; Sierpe, Víctor (2010). "New evidence of the sabertooth cat Smilodon (Carnivora: Machairodontinae) in the late Pleistocene of southern Chilean Patagonia". Revista Chilena de Historia Natural. 83 (2). doi:10.4067/S0716-078X2010000200010.
- "Two New Studies of Sabertooth (Smilodon fatalis) Anatomy". July 8, 2011.
- Fiedel, Stuart (2009). "Sudden Deaths: The Chronology of Terminal Pleistocene Megafaunal Extinction" (PDF). In Haynes, Gary (ed.). American Megafaunal Extinctions at the End of the Pleistocene. Springer. pp. 21–37. doi:10.1007/978-1-4020-8793-6_2. ISBN 978-1-4020-8792-9.