Machairodontinae

Machairodontinae is an extinct subfamily of carnivoran mammals that belonged to the cat family Felidae. These animals are often called "saber-toothed cats" because of their long, sharp teeth, especially the upper maxillary canines. They varied greatly in size, from about the size of a lynx to larger than a lion.

These cats lived during the Middle Miocene to the Early Pliocene, spreading across many continents except Australia and Antarctica. They were top predators in their environments.

Eventually, machairodontines began to disappear, possibly due to changes in climate, less food, and competition with newer big cats and early humans. The last of these animals, such as Smilodon and Homotherium, went extinct around 12-10,000 years ago during a major event that affected many large animal species.

Evolution

A male Amphimachairodus giganteus was one of the largest machairodonts. It dwarfs its modern relative, the common house cat, Felis catus.

Machairodontines were an ancient group of cats that lived millions of years ago. They were part of the cat family, Felidae. They were an early branch that split off from the ancestors of today's cats about 20 million years ago. These cats are known for their long teeth, often called "saber-teeth." Not all of them had teeth this long. Some, like Smilodon, had very long teeth. Others, like Dinofelis, had shorter ones.

These cats first appeared in Europe during a time called the Miocene. Over time, they spread to other places like Africa and Turkey. Scientists used to think there were three main groups of machairodontines. Newer studies show that some of these groups might not be as separate as once thought. Machairodontines were not related to tigers, even though people sometimes call them "saber-toothed tigers." They looked different and hunted in their own special ways.

Subfamily †Machairodontinae
Tribe	Genus	Species
Incertae sedis	†Tchadailurus Bonis et al., 2018	†T. adei
†Homotherini	†Amphimachairodus Kretzoi, 1929	†A. alvarezi †A. coloradensis †A. giganteus †A. kurteni †A. hezhengensis †A. horribilis
	†Homotherium Fabrini, 1890	†H. ischyrus †H. latidens †H. serum †H. venezuelensis
	†Lokotunjailurus Werdelin 2003	†L. emageritus †L. fanonei †L. chinsamyae
	†Nimravides Kitts 1958	†N. catacopsis †N. galiani †N. hibbardi †N. pedionomus †N. thinobates
	†Xenosmilus Martin et al., 2000	†X. hodsonae
†Machairodontini	†Hemimachairodus Koenigswald, 1974	†H. zwierzyckii
	†Machairodus Kaup, 1833	†M. alberdiae †M. aphanistus †M. laskerevi †M. robinsoni
	†Longchuansmilus Jiangzuo et al 2022	†L. xingyongi
	†Adeilosmilus Jiangzuo, Werdelin, Sun et al 2022	†A. kabir
	†Taowu Jiangzuo, Werdelin, Sun et al 2022	†T. liui
	†Miomachairodus Schmidt-Kittler 1976	†M. pseudaeluroides
†Metailurini	†Adelphailurus Hibbard, 1934	†A. kansensis
	†Dinofelis Zdansky, 1924	†D. aronoki †D. barlowi †D. cristata †D. darti †D. diastemata †D. paleoonca †D. petteri †D. piveteaui †D. werdelini
	†Metailurus Zdansky, 1924	†M. boodon †M. major †M. mongoliensis †M. ultimus †M. hengduanshanensis
	†Stenailurus Crusafont-Pairo & Aguirre, 1972	†S. teilhardi
	†Fortunictis Pons-Moyà 1987	†F. acerensis
	†Yoshi Spassov and Geraads, 2014	†Y. garevskii †Y. minor †Y. faie †Y. obscura †Y. youngdengensis
†Smilodontini	†Megantereon Croizet & Jobert, 1828	†M. cultridens †M. ekidoit †M. hesperus †M. inexpectatus †M. microta †M. nihowanensis †M. vakhshensis †M. whitei
	†Paramachairodus Pilgrim, 1913	†P. maximiliani †P. orientalis †P. transasiaticus †P. yingliangi
	†Promegantereon Kretzoi, 1938	†P. ogygia
	†Rhizosmilodon Wallace & Hulbert, 2013	†R. fiteae
	†Smilodon Lund, 1842	†S. fatalis †S. gracilis †S. populator

Fossil remains

The skulls of machairodonts, especially their teeth, are the most studied parts of these ancient cats. They had two types: dirk-toothed cats with long, narrow upper teeth and scimitar-toothed cats with shorter, broader teeth. Some, like Smilodon, had very long teeth, while others, like Dinofelis, had shorter ones.

Machairodonts had fewer teeth than modern cats because they ate meat. Most had six small teeth, two long teeth, and six middle teeth in each jaw, with only two back teeth in the top jaw. Their longer teeth needed bigger gaps in their skulls, which changed the shape of their jaw muscles and bones. This let them open their mouths wider than modern cats.

The bodies of dirk-toothed machairodonts, like Smilodon, were sturdy and strong, with shorter tails and wide ribcages. Scimitar-toothed machairodonts were more varied, with some being long-legged and lean, like Homotherium, and others, like Xenosmilus, having a mix of traits from both groups. In 2020, scientists found a preserved cub of the species Homotherium latidens in Yakutia, Russia, which was a rare and exciting discovery.

Derived anatomy and diet

Machairodonts, especially those with long teeth like Smilodon and Megantereon, had weaker jaws than modern lions. Their jaw muscles were not as strong, but their neck muscles helped them use their long teeth when hunting.

Studies of Smilodon fossils show that they mainly ate bison and horses, and sometimes ground sloths and mammoths. They were good at taking meat from bones and could eat smaller bones, like modern lions. Scientists have studied the faces of these cats and think they might have had longer lips to help with their large teeth, though this idea is not certain. Comparisons of their hyoid bones suggest they might have made sounds similar to modern cats.

Main article: Stable isotope analysis

Main articles: sagittal crest, pinnae, rhinarium, jowls, hyoid

Social behavior

Main article: Smilodon § Social behavior

Scientists have studied whether Smilodon, a type of saber-toothed cat, lived in groups or alone. They looked at fossils from California’s La Brea tar pits and compared them to modern animals in Africa. The fossils suggest Smilodon might have been social because many were found together, similar to lions. But some experts think Smilodon had a small brain, which might mean it wasn’t very social.

Another saber-toothed cat, Homotherium, may have hunted in groups too. Fossils found in Texas show Homotherium might have hunted young mammoths together and brought them to caves to eat safely. Evidence from injuries also suggests these cats might have lived in groups, helping each other survive.

Functionality of the sabers

Scientists have wondered how machairodonts, often called saber-toothed cats, used their long teeth. One idea is that they used these teeth like knives to stab their prey. But teeth are fragile and could break easily against hard bones, so this idea is not widely accepted today.

Another idea is that the long teeth were not for hunting but for showing off, like a lion's mane. This would help in finding mates or showing status. But since both male and female machairodonts had these teeth, this idea also has problems.

Some believe machairodonts were scavengers, finding dead animals to eat instead of hunting them. This would mean their teeth were not needed for killing, and they could use their good smell and hearing to find food left by other animals.

A more accepted idea is that machairodonts used a special bite to the throat of their prey. Instead of just clamping the throat like modern cats, they might have caused damage with their teeth. This could make the prey bleed and die quickly. However, this method could also attract other predators to the scene.

One specific idea is that machairodonts could bite the neck and then leave the prey to bleed to death. Another idea is that they could bite and compress the throat, causing both suffocation and injury.

Some scientists think machairodonts could tear open the belly of their prey. This would require several cats working together to hold the prey still while one cat bit into the belly. This method could cause bleeding and death quickly, and it might be safer for the cats because the belly is softer than the neck. However, this method also has problems, such as the risk of being kicked by the prey or not being able to grip large animals properly.

Notes and references

A study about the extinct saber-toothed cats was published in Current Biology. The report, by Ross Barnett and others, discussed the evolution of these ancient cats.