Saber-toothed predator

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From top and from left to right, Inostrancevia, Hoplophoneus, Barbourofelis, Smilodon, Machaeroides and Thylacosmilus Saber tooth 2.jpg
From top and from left to right, Inostrancevia , Hoplophoneus , Barbourofelis , Smilodon , Machaeroides and Thylacosmilus

A saber-tooth (alternatively spelled sabre-tooth) is any member of various extinct groups of predatory therapsids, predominantly carnivoran mammals, that are characterized by long, curved saber-shaped canine teeth which protruded from the mouth when closed. Saber-toothed mammals have been found almost worldwide from the Eocene epoch to the end of the Pleistocene epoch (42 million years ago – 11,000 years ago). [1] [2] [3]

Contents

One of the best-known genera is the machairodont or "saber-toothed cat" Smilodon , the species of which, especially S. fatalis, are popularly referred to as "saber-toothed tigers", although they are not closely related to tigers ( Panthera ). Despite some similarities, not all saber-tooths are closely related to saber-toothed cats or felids in-general. Instead, many members are classified into different families of Feliformia, such as Barbourofelidae and Nimravidae; [4] the oxyaenid "creodont" genera Machaeroides and Apataelurus ; and two extinct lineages of metatherian mammals, the thylacosmilids of Sparassodonta, and deltatheroideans, which are more closely related to marsupials. In this regard, these saber-toothed mammals can be viewed as examples of convergent evolution. [5] This convergence is remarkable due not only to the development of elongated canines, but also a suite of other characteristics, such as a wide gape and bulky forelimbs, which is so consistent that it has been termed the "saber-tooth suite." [6]

Of the feliform lineages, the family Nimravidae is the oldest, entering the landscape around 42 mya and becoming extinct by 7.2 mya. Barbourofelidae entered around 16.9 mya and were extinct by 9 mya. These two would have shared some habitats.

Morphology

The different groups of saber-toothed predators evolved their saber-toothed characteristics entirely independently. They are most known for having maxillary canines which extended down from the mouth when the mouth was closed. Saber-toothed cats were generally more robust than today's cats and were quite bear-like in build. They are believed to have been excellent hunters, taking animals such as sloths, mammoths, and other large prey. Evidence from the numbers found at the La Brea Tar Pits suggests that Smilodon , like modern lions, was a social carnivore. [7]

The first saber-tooths to appear were non-mammalian synapsids, such as the gorgonopsids; they were one of the first groups of animals within Synapsida to experience the specialization of saber teeth, and many had long canines. Some had two pairs of upper canines with two jutting down from each side, but most had one pair of upper extreme canines. Because of their primitiveness, they are extremely easy to tell from machairodonts. Several defining characteristics are a lack of a coronoid process, many sharp "premolars" more akin to pegs than scissors, and very long skulls. Despite their large canines, however, most gorgonopsians probably lacked the other specializations found in true saber-toothed predator ecomorphs. [8] Two gorgonopsians, Smilesaurus and Inostrancevia , had exceptionally large canines and may have been closer functional analogues to later sabertooths.

The second appearance is in Deltatheroida, a lineage of Cretaceous metatherians. At least one genus, Lotheridium , possessed long canines, and given both the predatory habits of the clade as well as the generally incomplete material, this may have been a more widespread adaptation. [9]

The third appearance of long canines is Thylacosmilus , which is the most distinctive of the saber-tooth mammals and is also easy to tell apart. It differs from machairodonts in possessing a very prominent flange and a tooth that is triangular in cross section. The root of the canines is more prominent than in machairodonts and a true sagittal crest is absent.

The fourth instance of saber-teeth is from the clade Oxyaenidae. The small and slender Machaeroides bore canines that were thinner than in the average machairodont. Its muzzle was longer and narrower.

The fifth saber-tooth appearance is the ancient feliform (carnivoran) family Nimravidae. Both groups have short skulls with tall sagittal crests, and their general skull shape is very similar. Some have distinctive flanges, and some have none at all, so this confuses the matter further. Machairodonts were almost always bigger, though, and their canines were longer and more stout for the most part, but exceptions do appear.

The sixth appearance is the barbourofelids. These feliform carnivorans are very closely related to actual cats. The best-known barbourofelid is the eponymous Barbourofelis , which differs from most machairodonts by having a much heavier and more stout mandible, smaller orbits, massive and almost knobby flanges, and canines that are farther back. The average machairodont had well-developed incisors, but barbourofelids' were more extreme.

The seventh and last saber-toothed group to evolve were the machairodonts themselves.

Diet

Reconstruction of a Smilodon Smilodon fatalis.jpg
Reconstruction of a Smilodon

The evolution of enlarged canines in Tertiary carnivores was a result of large mammals being the source of prey for saber-toothed predators. The development of the saber-toothed condition appears to represent a shift in function and killing behavior, rather than one in predator-prey relations. Many hypotheses exist concerning saber-tooth killing methods, some of which include attacking soft tissue such as the belly and throat, where biting deep was essential to generate killing blows. The elongated teeth also aided with strikes reaching major blood vessels in these large mammals. However, the precise functional advantage of the saber-tooth's bite, particularly in relation to prey size, is a mystery. A new point-to-point bite model is introduced in the article by Andersson et al., showing that for saber-tooth cats, the depth of the killing bite decreases dramatically with increasing prey size. [10] The extended gape of saber-toothed cats results in a considerable increase in bite depth when biting into prey with a radius of less than 10 cm. For the saber-tooth, this size-reversed functional advantage suggests predation on species within a similar size range to those attacked by present-day carnivorans, rather than "megaherbivores" as previously believed.

A disputing view of the cat's hunting technique and ability is presented by C. K. Brain in The Hunters or the Hunted?, in which he attributes the cat's prey-killing abilities to its large neck muscles rather than its jaws. [11] Large cats use both the upper and lower jaw to bite down and bring down the prey. The strong bite of the jaw is accredited to the strong temporalis muscle that attach from the skull to the coronoid process of the jaw. The larger the coronoid process, the larger the muscle that attaches there, so the stronger the bite. As C.K. Brain points out, the saber-toothed cats had a greatly reduced coronoid process and therefore a disadvantageously weak bite. The cat did, however, have an enlarged mastoid process, a muscle attachment at the base of the skull, which attaches to neck muscles. According to C.K. Brain, the saber-tooth would use a "downward thrust of the head, powered by the neck muscles" to drive the large upper canines into the prey. This technique was "more efficient than those of true cats". [11]

Biology

The similarity in all these unrelated families involves the convergent evolution of the saber-like canines as a hunting adaptation. Meehan et al. [12] note that it took around 8 million years for a new type of saber-toothed cat to fill the niche of an extinct predecessor in a similar ecological role; this has happened at least four times with different families of animals developing this adaptation. Although the adaptation of the saber-like canines made these creatures successful, it seems that the shift to obligate carnivorism, along with co-evolution with large prey animals, led the saber-toothed cats of each time period to extinction. As per Van Valkenburgh, the adaptations that made saber-toothed cats successful also made the creatures vulnerable to extinction. In her example, trends toward an increase in size, along with greater specialization, acted as a "macro-evolutionary ratchet": when large prey became scarce or extinct, these creatures would be unable to adapt to smaller prey or consume other sources of food, and would be unable to reduce their size so as to need less food. [13]

More recently, it has been suggested that Thylacosmilus differed radically from its placental counterparts in possessing differently shaped canines and lacking incisors. This suggests that it was not ecologically analogous to other saber-teeth and possibly an entrail specialist. [14] Another study has found that other saber toothed species similarly had diverse lifestyles and that superficial anatomical similarities obscure them. [15]

Phylogeny of feliform saber-tooths

The following cladogram shows the relationships between the feliform saber-tooths, including the Nimravidae, Barbourofelidae and Machairodontinae. [16] [17] Saber-toothed groups are marked with background colors.

Nimravidae

Dinictis felina

Pogonodon platycopis

Eusmilus

Eusmilus olsontau

Eusmilus villebramarensis

Eusmilus cerebralis

Hoplophoneus dakotensis

Hoplophoneus primaevus

Hoplophoneus occidentalis

Nanosmilus kurténi

Eofelis edwardsii

Nimravus brachyops

("false sabertoothed cats")

Haplogale media

Barbourofelidae
Barbourofelis

Barbourofelis morrisi

Barbourofelis fricki

Barbourofelis loveorum

Barbourofelis whitfordi

Sansanosmilus vallesiensis

("false sabertoothed cats")
Felidae

Proailurus lemanensis

" Pseudaelurus "

Hyperailuricitis skinneri

Nimravides

Nimravides pedionomus

Nimravides thinobates

Hyperailuricitis intrepidus

Hyperailuricitis validus

Pseudaelurus quadridentatus

Machairodontinae
Machairodus

Machairodus aphanistus

Machairodus horribilis

Amphimachairodus

Amphimachairodus kurteni

Amphimachairodus kabir

Amphimachairodus giganteus

Lokotunjailurus emageritus

Homotheriini
Dinobastis

Dinobastis serus

Dinobastis venezuelensis

Xenosmilus hodsonae

Homotherium latidens

(scimitar‑toothed cats)
Metailurini
Dinofelis

Dinofelis petteri

Dinofelis paleoonca

Dinofelis cristata

Metailurus

Metailurus major

Metailurus parvulus

Promegantereon ogygia

Smilodontini
Megantereon

Megantereon whitei

Megantereon cultridens

Megantereon ekidoit

Megantereon hesperus

Smilodon

Smilodon fatalis

Smilodon populator

Smilodon gracilis

(dirk‑toothed cats)
(sabertoothed cats)
Styriofelis

Styriofelis lorteti

Styriofelis turnauensis

Felinae sensu lato (includes all extant pantherines and felines)

(grade)

Saber-tooth genera

Genus Name Species Appeared
(Ma   BP)
Died out
(Ma BP)
RegionsCanine size
Smilodon 3–52.50.01North and South America17–30 cm
Hoplophoneus 533.723.8North and South America
Eusmilus 330.528Eurasia and North America
Dinictis 44025North America
Dinaelurus 1 ? ?North America
Dinailurictis 1 ? ? ?
Eofelis 2 ? ? ?
Nimravidus(Nimravides)2 ? ? ?
Nimravus (Nimravinus)633.520Europe and North America
Nimraviscus 1 ? ? ?
Pogonodon 2156Europe and North America
Quercylurus 1 ? ? ?
Archaelurus 1 ? ? ?
Aelurogale (Ailurictis)1 ? ? ?
Ictidailurus 1 ? ? ?
Albanosmilus 3183Eurasia and Africa
Afrosmilus 12510Africa
Barbourofelis 7153Eurasia and Africa
Ginsburgsmilus 12310Africa
Prosansanosmilus 2185Eurasia and Africa
Sansanosmilus 3123Eurasia and Africa
Syrtosmilus 1238Africa
Vampyrictis 1153Eurasia and Africa
Vishnusmilus 1 ? ? ?
Homotherium 1030.01Eurasia, Africa, North America, South America
Thylacosmilus 2101.8South Americaover 30 cm
Metailurus 9158Eurasia
Adelphailurus 1235North America
Paramachairodus 320–159Europe
Machairodus 18152Eurasia, Africa, North America
Miomachairodus 113.655.33Eurasia, Africa, North America
Amphimachairodus 4late Miocene ?Eurasia, North Africa, North America
Hemimachairodus 1PleistocenePleistoceneJava
Lokotunjailurus 1late Miocenelate MioceneAfrica
Megantereon 830.5Eurasia, Africa, North America
Dinofelis 651.5Eurasia, Africa, North America
Therailurus 152Eurasia, Africa, North America
Pontosmilus 4209Eurasia
Proailurus 23020Europe and North America
Pseudaelurus 12010Europe and North America
Xenosmilus 11.71North America
Stenailurus 1 ? ? ?
Epimachairodus 1 ? ? ?
Hemimachairodus 1 ? ? ?
Ischyrosmilus 1 ? ? ?

Saber-tooth taxonomy

All saber-toothed mammals lived between 33.7 million and 9,000 years ago, but the evolutionary lines that led to the various saber-tooth genera started to diverge much earlier. It is thus a polyphyletic grouping.

The lineage that led to Thylacosmilus was the first to split off, in the late Cretaceous. It is a metatherian, and thus more closely related to kangaroos and opossums than the felines. The hyaenodonts diverged next, possibly before Laurasiatheria, then the oxyaenids, and then the nimravids, before the diversification of the truly feline saber-tooths.

Related Research Articles

<i>Machairodus</i> Extinct genus of carnivores

Machairodus is a genus of large machairodont or ''saber-toothed cat'' that lived in Africa, Eurasia and North America during the late Miocene. It is the animal from which the subfamily Machairodontinae gets its name and has since become a wastebasket taxon over the years as many genera of sabertooth cat have been and are still occasionally lumped into it.

<i>Smilodon</i> Extinct genus of saber-toothed cat

Smilodon is a genus of felids belonging to the 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. 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.

<i>Homotherium</i> Extinct genus of carnivores

Homotherium is an extinct genus of machairodontine scimitar-toothed cat that inhabited North America, South America, Eurasia, and Africa during the Pliocene and Pleistocene epochs from around 4 million to 12,000 years ago. In comparison to Smilodon, the canines of Homotherium were shorter, and it was probably adapted to running down rather than ambushing prey.

<span class="mw-page-title-main">Nimravidae</span> Extinct family of mammals in the order Carnivora

Nimravidae is an extinct family of carnivorans, sometimes known as false saber-toothed cats, whose fossils are found in North America and Eurasia. Not considered to belong to the true cats, the nimravids are generally considered closely related and classified as a distinct family in the suborder Feliformia. Fossils have been dated from the Middle Eocene through the Late Miocene epochs, spanning about 33.2 million years.

<span class="mw-page-title-main">Machairodontinae</span> Extinct subfamily of carnivores

Machairodontinae is an extinct subfamily of carnivoran mammals of the family Felidae. They were found in Asia, Africa, North America, South America, and Europe from the Miocene to the Pleistocene, living from about 16 million until about 10,000 years ago.

<span class="mw-page-title-main">Smilodontini</span> Extinct tribe of carnivores

Smilodontini is an extinct tribe within the Machairodontinae or "saber-toothed cat" subfamily of the Felidae. The tribe is also known as the "dirk-toothed cats". They were endemic to South America, North America, Europe, Asia, and Africa during the Miocene to Pleistocene, from 10.3 mya—11,000 years ago, existing for approximately 10.3 million years.

<i>Xenosmilus</i> Extinct genus of carnivores

Xenosmilus is an extinct genus of homotherin machairodontine that was discovered in Florida in 2001. It has one species, Xenosmilus hodsonae.

<i>Thylacosmilus</i> Extinct genus of mammals

Thylacosmilus is an extinct genus of saber-toothed metatherian mammals that inhabited South America from the Late Miocene to Pliocene epochs. Though Thylacosmilus looks similar to the "saber-toothed cats", it was not a felid, like the well-known North American Smilodon, but a sparassodont, a group closely related to marsupials, and only superficially resembled other saber-toothed mammals due to convergent evolution. A 2005 study found that the bite forces of Thylacosmilus and Smilodon were low, which indicates the killing-techniques of saber-toothed animals differed from those of extant species. Remains of Thylacosmilus have been found primarily in Catamarca, Entre Ríos, and La Pampa Provinces in northern Argentina.

<i>Dinictis</i> Extinct genus of carnivores

Dinictis is a genus of the Nimravidae, an extinct family of feliform mammalian carnivores, also known as "false saber-toothed cats". Assigned to the subfamily Nimravinae, Dinictis was endemic to North America from the Late Eocene to Early Miocene epochs, existing for about 16.8 million years.

<i>Barbourofelis</i> Extinct genus of carnivores

Barbourofelis is an extinct genus of large, predatory, feliform carnivoran mammals of the family Barbourofelidae. The genus was endemic to North America and Eurasia during the Miocene until its extinction during the Tortonian, living from 13.6 to 4.9 Ma.

<span class="mw-page-title-main">Barbourofelidae</span> Extinct family of feliform carnivorans

Barbourofelidae is an extinct family of carnivorans of the suborder Feliformia, sometimes known as false saber-toothed cats, that lived in North America, Eurasia and Africa during the Miocene epoch and existed for about 7.9 million years. Thought to be an independent lineage from the Nimravidae and Machairodontinae, which had all attained elongated canines, recent research argues that it may be a subfamily of the Nimravidae, extending its biochronological range into the Miocene, although this issue is not yet fully resolved.

<span class="mw-page-title-main">Feliformia</span> Suborder of carnivores

Feliformia is a suborder within the order Carnivora consisting of "cat-like" carnivorans, including cats, hyenas, mongooses, viverrids, and related taxa. Feliformia stands in contrast to the other suborder of Carnivora, Caniformia.

<i>Machaeroides</i> Extinct genus of carnivores

Machaeroides ("dagger-like") is an extinct genus of sabre-toothed predatory placental mammals from extinct subfamily Machaeroidinae within extinct family Oxyaenidae, that lived in North America (Wyoming) from the early to middle Eocene.

Dinaelurus is a genus of the Nimravidae, an extinct family of feliform mammalian carnivores, also known as "false saber-toothed cats". Assigned to subfamily Nimravinae, Dinaelurus was endemic to North America during the Eocene-Oligocene epochs, existing for approximately 10.2 million years.

Quercylurus major is an extinct, cat-like nimravid carnivora from the early Oligocene of France. Its fossils were found in Early Oligocene strata in Quercy. Q. major was possibly the largest nimravid ever known, as its fossils suggest it was similar in size to the modern-day lion.

The cat gap is a period in the fossil record of approximately 25 million to 18.5 million years ago in which there are few fossils of cats or cat-like species found in North America. The cause of the "cat gap" is disputed, but it may have been caused by changes in the climate, changes in the habitat and environmental ecosystem, the increasingly hypercarnivorous trend of the cats, volcanic activity, evolutionary changes in dental morphology of the Canidae species present in North America, or a periodicity of extinctions called van der Hammen cycles.

<i>Mentoclaenodon</i>

Mentoclaenodon is an extinct genus of arctocyonid ungulate mammals.

<span class="mw-page-title-main">Thylacosmilidae</span> Extinct family of mammals

Thylacosmilidae is an extinct family of metatherian predators, related to the modern marsupials, which lived in South America between the Miocene and Pliocene epochs. Like other South American mammalian predators that lived prior to the Great American Biotic Interchange, these animals belonged to the order Sparassodonta, which occupied the ecological niche of many eutherian mammals of the order Carnivora from other continents. The family's most notable feature are the elongated, laterally flattened fangs, which is a remarkable evolutionary convergence with other saber-toothed mammals like Barbourofelis and Smilodon.

<span class="mw-page-title-main">Homotherini</span> Extinct tribe of carnivores

Homotherini is a tribe of saber-toothed cats of the family Felidae. The tribe is commonly known as scimitar-toothed cats. These saber-toothed cats were distributed en North America, Europe, Asia, Africa, and South America from the Miocene to Pleistocene living from c. 23 Ma until c. 12,000 years ago.

<i>Amphimachairodus</i> Extinct genus of carnivores

Amphimachairodus is an extinct genus of large machairodonts. It is also a member of the tribe Homotherini within Machairodontinae and is most closely related to such genera as Xenosmilus, Homotherium itself, and Nimravides. It inhabited Eurasia, Northern Africa and North America during the late Miocene epoch.

References

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Further reading