Machairodontinae

Taxobox
name = Machairodontinae
fossil_range = Early Miocene to Late Pleistocene

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image_width = 250px
image_caption = "Smilodon californicus" fossil at the
National Museum of Natural History, Washington, DC
regnum = Animalia
phylum = Chordata
classis = Mammalia
ordo = Carnivora
familia = Felidae
subfamilia = †Machairodontinae
subfamilia_authority = Gill, 1872
subdivision_ranks = Tribes
subdivision = †Machairodontini
†SmilodontiniThe Machairodontinae form a subfamily of the Felidae (true cats). It contains some of the extinct cats commonly known as "saber-toothed cats", including the famed genus "Smilodon" as well as other cats with only minor increases in the size and length of their maxillary canines. Sometimes other carnivorous mammals with elongated teeth are also called saber-toothed cats, although they do not belong to the felids. Besides the machairodonts, saber-toothed predators arose in the Nimravidae, the Barbourofelidae, the Creodonta ("Machaeroides") and even in the Marsupials ("Thylacosmilus")Lars W. van den Hoek Ostende, Michael Morlo, Doris Nagel: "Fossils explained 52 Majestic killers: the sabre-toothed cats." Blackwell Publishing Ltd, Geology Today, Vol. 22, No. 4, July–August 2006 [http://www.blackwell-synergy.com/doi/abs/10.1111/j.1365-2451.2006.00572.x online] ] .

Evolution

The Machairodontinae originated in the early or middle Miocene of Africa. The early felid "Pseudaelurus quadridentatus" showed a trend towards elongated upper canines and is believed to be at the base of the machairodontine evolution [Jordi Augusti: "Mammoths, Sabertooths and Hominids 65 Million Years of Mammalian Evolution in Europe", Columbia University Press, 2002. ISBN 0-231-11640-3] . The earliest known machairodontid genus is the middle Miocene "Miomachairodus" from Africa and Turkey [cite journal | author = Lars W. van den Hoek Ostende, Michael Morlo & Doris Nagel | title = Fossils explained 52 Majestic killers: the sabre-toothed cats | journal = Geology Today | volume = 22 | issue = 4 | pages = 150 | month = July | yeah = 2006] . Until the late Miocene machairodontines co-existed at several places together with barbourofelids, archaic large carnivores, bearing also long sabreteeth Lars W. van den Hoek Ostende, Michael Morlo, Doris Nagel: "Fossils explained 52 Majestic killers: the sabre-toothed cats." Blackwell Publishing Ltd, Geology Today, Vol. 22, No. 4, July–August 2006 [http://www.blackwell-synergy.com/doi/abs/10.1111/j.1365-2451.2006.00572.x online] ] . Traditionally three different tribes of machairodontines were recognized, the Smilodontini with typical dirk-toothed forms like "Megantereon" and "Smilodon", the Machairodontini or Homotherini with scimitar-toothed cats like "Machairodus" or "Homotherium" and the Metailurini, containing generea like "Dinofelis" and "Metailurus". However, recently the Metailurini are grouped within another felid subfamily, the Felinae, not into the Machairodontinae Lars W. van den Hoek Ostende, Michael Morlo, Doris Nagel: "Fossils explained 52 Majestic killers: the sabre-toothed cats." Blackwell Publishing Ltd, Geology Today, Vol. 22, No. 4, July–August 2006 [http://www.blackwell-synergy.com/doi/abs/10.1111/j.1365-2451.2006.00572.x online] ] . The last machairodontine genera "Smilodon" and "Homotherium" disappeared not until the latest Pleistocene, roughly 10.000 years ago in the Americas.

The name 'saber-toothed tigers' is misleading. Machairodonts were not even in the same subfamily as tigers, there is no evidence that they had tiger-like coat patterns, and this broad group of animals certainly did not all live or hunt in the same manner as the modern tiger. DNA analysis published in 2005 confirmed and clarified cladistic analysis in showing that the Machairodontinae diverged early from the ancestors of modern cats and are not closely related to any living feline species Lars W. van den Hoek Ostende, Michael Morlo, Doris Nagel: "Fossils explained 52 Majestic killers: the sabre-toothed cats." Blackwell Publishing Ltd, Geology Today, Vol. 22, No. 4, July–August 2006 [http://www.blackwell-synergy.com/doi/abs/10.1111/j.1365-2451.2006.00572.x online] ] . Sabertooths also coexisted in many places together with conical-toothed cats. In Africa and Eurasia, sabertooths competed with several pantherines and cheetahs until the early or middle Pleistocene. "Homotherium" survived in Northern Europe even until the late Pleistocene. In the Americas they coexisted together with the cougar, American lion, American cheetah, and jaguar until the latest Pleistocene. Saber-toothed and conical-toothed cats competed with each other for food resources, until the last of the former became extinct. All recent felids have more or less conical-shaped upper canines.

Teeth

Machairodonts are divided into two types: dirk-toothed and scimitar-toothed. Dirk-toothed cats had elongated, narrow upper canines and generally had stocky bodies. Scimitar-toothed cats had broader and shorter upper canines and a typically lithe body form with longer legs. The longer-toothed cats often had a bony flange that extended from their lower mandible. However, one genus, "Xenosmilus", known only from two fairly complete fossils, broke this mould, possessing both the stout heavy limbs associated with dirk-toothed cats, and the stout canines of a scimitar-toothed cat.

Hunting techniques

The method by which machairodonts hunted is hotly debatedFact|date=September 2008. It was originally thoughtFact|date=September 2008 that they used a 'stabbing' motion with their teeth (dropping their jaws wide open, baring their teeth, and thrashing downward). However, this is now considered unlikelyFact|date=September 2008, for the teeth, being so long, were fragile, and a large prey animal thrashing about could easily injure the teeth, which would impair hunting. Some scientists suggestFact|date=September 2008 that the cats slashed at the bellies of large animals with their teeth and waited for them to die of blood loss, although the risk of breakage would still be high. When the bite of a dirk toothed cat is matched against the neck of a large ungulate, however, it shows that the bite would sever all arteries and veins, while acting as a clamp around the windpipeFact|date=September 2008. This method would still have been risky for the teeth if the prey moved too much, but less risky than the stabbing method; with the neck bite, the cat would be anchored with its incisors and lower canines. Also, if the cats worked in prides (there is evidence that some species may haveFact|date=September 2008), they could have subdued the animal before performing the killing bite.

Genera

The genera of Machairodontines [McKenna, M., Bell, K.,: Classification of Mammals: Above the Species Level. Columbia University Press; Auflage: New Ed; 2000.] :

Machairodontini

*"Machairodus": Miocene; Eurasia, Africa and North America
*"Homotherium": early Pliocene [Alan Turner: "The Evolution of the guild of larger terrestrial carnivores during the Plio-Pleistocene in Africa". Geobios, no 23, fasc. 3, p. 349-368, 1990.] to latest Pleistocene; Eurasia, Africa, North America and South America
*"Xenosmilus": early Pleistocene; North America [ L. D. Martin et al.: "Three Ways To Be a Saber-Toothed Cat." Naturwissenschaften, Springer Berlin / Heidelberg, 1999. [http://www.springerlink.com/content/h0h54wfnbvuanqvg/fulltext.pdf online] ]
*"Lokontailurus": late Miocene; AfricaLars W. van den Hoek Ostende, Michael Morlo, Doris Nagel: "Fossils explained 52 Majestic killers: the sabre-toothed cats." Blackwell Publishing Ltd, Geology Today, Vol. 22, No. 4, July–August 2006 [http://www.blackwell-synergy.com/doi/abs/10.1111/j.1365-2451.2006.00572.x online] ]
*"Miomachairodus": middle Miocene; North Africa, Turkey
*"Hemimachairodus": Pleistocene; Java

Smilodontini
*"Paramachairodus" [cite book |last=Turner |first=Alan |year=1997 |title= The Big Cats and their fossil relatives|publisher= Columbia University Press|location=New York|pages= 60|isbn= 0-231-10228-3] : middle to late Miocene; Europe and Asia
*"Megantereon": early Pliocene to middle Pleistocene; Europe, Asia, Africa and North America
*"Smilodon": late Pliocene to latest Pleistocene, North and South America

Notes and References

* [http://www.eurekalert.org/pub_releases/2005-08/cp-dte080305.php Report on Barnett group's study in "Current Biology" August 9, 2005] : Ross Barnett et al.: "Evolution of the extinct Sabretooths and the American cheetah-like cat" in "Current Biology", Vol. 15, R589-R590, August 9, 2005