Saber-toothed cat

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A Smilodon skull on display at the American Museum of Natural History

A saber-toothed cat (alternatively spelled sabre-toothed cat),[1] also misleadingly known as a saber-toothed tiger,[2][3] is any of various groups of predatory mammals related to modern cats (or resembling cats) that were characterized by long, curved saber-shaped canine teeth. These animals belong to taxa of Machairodontinae (Felidae), Barbourofelidae and Nimravidae (both Feliformia), as well as two families related to marsupials that were found worldwide from the Eocene epoch to the end of the Pleistocene epoch (42 mya – 11,000 years ago), existing for about 42 million years.[4][5][6] The large maxillary canine teeth extended from the mouth even when it was closed. Despite the name, not all animals known as saber-toothed cats were closely related to modern felines.

The Nimravidae are 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

These subfamilies evolved their saber-toothed characteristics entirely independently. They are most known for having maxillary canines which were, in some species, up to 50 cm (19.7 inches) long and extended down from the mouth even when the mouth was closed. Sabre-toothed cats were generally more robust than today's cats and were quite bear-like in build. They were believed to be excellent hunters and hunted animals such as sloths, mammoths, and other large prey. Evidence from the numbers found at La Brea Tar Pits suggests that Smilodon, like modern lions, was a social carnivore.[7]

The first late saber-tooth instance is a group of animals ancestral to mammals but not yet mammals. Known as synapsids or mammal-like reptiles, they were one of the first groups of animals to experience specialization of 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. With no cononoid process, many sharp "premolars" more like pegs than scissors and a very long, lizard-like head are among several characteristics that mark them out.

The second 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 a 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 third instance of saber teeth is from order Creodonta. The small and slender Machaeroides bore canines that were thinner than in the average machairodont. Its muzzle was longer and narrower.

The fourth saber-tooth appearance is the ancient family of carnivores, the nimravids, and they are notoriously hard to tell apart from machairodonts. Both groups have short skulls, 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 fifth appearance is the barbourofelids. These carnivores are very closely related to actual cats, and as such, they are hard to tell apart. The best known barbourofelid is Barbourofelis, which differs from most machairodonts by 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 sixth and last of the saber-tooth group to evolve were the machairodonts themselves.

Prey

Steps of reconstruction

Many of the saber-toothed cats' food sources were large mammals such as elephants, rhinos, and other colossal herbivores of the era. The evolution of enlarged canines in Tertiary carnivores was a result of large mammals being the source of prey for saber-toothed cats. 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-toothed cat'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. 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 sabre-tooth, this size-reversed functional advantage suggests predation on species within a similar size range to those attacked by present-day carnivorans, rather than "mega herbivores" 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. 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”.

Ecology

The similarity in all these unrelated families involves convergent evolution of the saber-like canines as a hunting adaptation. Meehan et al.[full citation needed] 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.[8]

Saber-tooth genera

FELIDAE

Proailurus 25 mya; Europe, Asia; one species; 9 kg




Pseudaelurus 18 mya; Europe, Asia, North America; 12 species; average 40 kg




Subfamily Felinae

(modern cats 10 mya – present; North America, South America, Europe, Asia, Africa; 44 species)


Subfamily Machairodontinae

Tribe Metailurini

Adelphailurus 10–5 mya; North America; one species; 50 kg



Pontosmilus four species



Stenailurus 7 mya; Europe




Metailurus 9 mya – 11,000 BCE; Africa, North America, Europe, Asia; six species



Dinofelis (aka Therailurus) 5–1 mya; Europe, Asia, Africa, North America; eight species; average 90 kg





Tribe Smilodontini

Paramachairodus (aka Paramegantereon, Promegantereon) 15–9 mya; Europe, Asia; two species; average 55 kg




Megantereon 6–2 mya; North America, Africa, Asia; 12 species; average 120 kg



Smilodon 2.5 mya – 10,000 BCE; North America, South America; three species; average 400 kg






Tribe Homotherini

Lokotunjailurus 10 mya; Africa




Homotherium 5 mya – 10,000 BCE; North America, South America, Europe, Asia, Africa; 14 species; average 190 kg



Xenosmilus 1 mya; North America; one species; 300 kg




Tribe Machairodontini

Miomachairodus 12 mya; Europe, Asia, Africa, North America; one species



Machairodus (aka Nimvarides, Amphimachairodus) 11 mya – 126,000 BCE; Europe, Asia, Africa, North America; 20 species; average 300 kg












Genus Name Species Appeared
(Ma BP)
Died out
(Ma BP)
Regions Canine Size
Smilodon 3–5 2.5 0.01 North & South America 17–30 cm
Hoplophoneus 5 33.7 23.8 North and South America
Eusmilus 3 30.5 28 Eurasia, North America
Dinictis 4 40 25 North America
Dinaelurus 1  ?  ? North America
Dinailurictis 1  ?  ?  ?
Eofelis 2  ?  ?  ?
Nimravidus (Nimravides) 2  ?  ?  ?
Nimravus (Nimravinus) 6 33.5 20 Europe, North America
Nimraviscus 1  ?  ?  ?
Pogonodon 2 15 6 Europe, North America
Quercylurus 1  ?  ?  ?
Archaelurus 1  ?  ?  ?
Aelurogale (Ailurictis) 1  ?  ?  ?
Ictidailurus 1  ?  ?  ?
Albanosmilus 3 18 3 Africa, Eurasia
Afrosmilus 1 25 10 Africa
Barbourofelis 7 15 3 Africa, Eurasia
Ginsburgsmilus 1 23 10 Africa
Prosansanosmilus 2 18 5 Africa, Eurasia
Sansanosmilus 3 12 3 Africa, Eurasia
Syrtosmilus 1 23 8 Africa
Vampyrictis 1 15 3 Africa, Eurasia
Vishnusmilus 1  ?  ?  ?
Homotherium 10 3 0.01 Africa, Eurasia, North & South America
Thylacosmilus (sparassodont) 2 10 1.8 South America over 30 cm
Metailurus 9 15 8 Eurasia
Adelphailurus 1 23 5 North America
Paramachairodus 3 20–15 9 Europe
Machairodus (Ancestral to Homotherium) 18 15 2 Africa, Eurasia, North America
Miomachairodus 1 13.65 5.33 Europe, Asia, Africa, North America
Hemimachairodus 1 Pleistocene Pleistocene Java
Lokotunjailurus 1 late Miocene late Miocene Africa
Megantereon 8 3 0.5 Africa, Eurasia, North America
Dinofelis 6 5 1.5 Africa, Eurasia, North America
Therailurus 1 5 2 Africa, Eurasia, North America
Pontosmilus 4 20 9 Eurasia
Proailurus 2 30 20 Europe, North America
Pseudaelurus 1 20 10 Europe, North America
Xenosmilus 1 1.7 1 North America
Stenailurus 1  ?  ?  ?
Epimachairodus 1  ?  ?  ?
Hemimachairodus 1  ?  ?  ?
Ischyrosmilus 1  ?  ?  ?

Saber-tooth evolutionary tree

All saber-tooth 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 marsupial, and thus more closely related to kangaroos and opossums than the felines. The creodonts diverged next, and then the nimravids, before the blossoming of the truly feline saber-tooths.

References

  1. ^ See for example "sabre-toothed cat" Encyclopædia Britannica. 2009. Encyclopædia Britannica Online. 26 Oct. 2009.
  2. ^ Pool, Bob (September 16, 2012). "What Is A Sabertooth". UC Berkeley. Retrieved 2012-06-12. "I remember reading about this as a kid. I can still remember seeing a picture of the saber-toothed tiger struggling in the tar" 
  3. ^ "What Is a Sabertooth?". University of California Museum of Paleontology. December 2005. Retrieved 2012-06-12. "The name "saber-toothed tiger" is misleading as these animals are not closely related to tigers." 
  4. ^ "PaleoBiology Database: ''Smilodon'', basic info". Paleodb.org. Retrieved 2012-09-06. 
  5. ^ "PaleoBiology Database: ''Nimravidae'', basic info". Paleodb.org. Retrieved 2012-09-06. 
  6. ^ "PaleoBiology Database: ''Barbourofelidae'', basic info". Paleodb.org. Retrieved 2012-09-06. 
  7. ^ Carbone, C.; Maddox, T.; Funston, P. J.; Mills, M. G.; Grether, G. F.; Van Valkenburgh, B. (2009). "Parallels between playbacks and Pleistocene tar seeps suggest sociality in an extinct sabretooth cat, Smilodon". Biol Lett. 5 (1): 81–85. doi:10.1098/rsbl.2008.0526. PMC 2657756. PMID 18957359. 
  8. ^ Van Valkenburgh, B. (2007). "Deja vu: the evolution of feeding morphologies in the Carnivora". Integrative and Comparative Biology 47 (1): 147–163. doi:10.1093/icb/icm016. 

Further reading

  • Anton, Mauricio (2013). Sabertooth. Bloomington: Indiana University Press. ISBN 0253010497. 

Sources

  • Andersson, K., Norman, D. and Werdelin, L. "Sabretoothed Carnivores and the Killing of Large Prey". PloS ONE 6.10 (2011): 1–6. Academic Search Premier. Web. 11 Oct. 2012. http://dx.doi.org/10.1371/journal.pone.0024971
  • Brain, C. K. "Part 2: Fossil Assemblages from the Sterkfontein Valley Caves: Analysis and Interpretation." The Hunters or the Hunted?: An Introduction to African Cave Taphonomy. Chicago: University of Chicago, 1981. N. pag. Print.
  • Meehan, T.J., Martin, L.D. "Extinction and Re-Evolution of Similar Adaptive Types (Ecomorphs) in Cenozoic North American Ungulates and Carnivores Reflect van der Hammen's Cycles". Naturwissenschaften (2003) 90:131–135. 07 Feb. 2003. http://dx.doi.org/10.1007/s00114-002-0392-1
  • Mol, D., W. v. Logchem, K. v. Hooijdonk, R. Bakker. The Saber-Toothed Cat. DrukWare, Norg 2008. ISBN 978-90-78707-04-2.
  • Sardella, R. "Web of Knowledge [v5.6]". SOC PALEONTOLOGICA ITALIANA, C/O E. SERPAGLI, EDITOR, IST DI PALEONTOLOGIA VIA UNIV 4, MODENA, 00000, ITALY, 10 Mar. 2012. Web. 18 Oct. 2012. <http://apps.webofknowledge.com/full_record.do?product=WOS>.
  • Van Valkenburgh, B. "Déjà vu: The Evolution of Feeding Morphologies in the Carnivora". Integrative and Comparative Biology. (2007) 47 1:147–163. 22 May 2007. http://dx.doi.org/10.1093/icm016

External links