Machairodontinae

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Machairodontinae Fossil range: Early Miocene to Late Pleistocene
Smilodon californicus fossil at the National Museum of Natural History, Washington, DC
Scientific classification
Kingdom: Animalia Phylum: Chordata Class: Mammalia Order: Carnivora Family: Felidae Subfamily: †Machairodontinae Gill, 1872
Tribes
†Machairodontini †Smilodontini

The 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)^[1].

Contents 1 Evolution 2 Teeth 3 Hunting techniques 4 Genera 5 Notes and References

[edit] Evolution

The Machairodontinae obviously 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 ^[2]. The earliest known machairodontid genus is the middle Miocene Miomachairodus from Africa and Turkey ^[3]. Until the late Miocene machairodontines co-existed at several places together with barbourofelids, archaic large carnivores, bearing also long sabreteeth ^[1]. 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 ^[1]. 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 ^[1]. 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 the coexisted together with 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.

[edit] 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 lither 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.

[edit] Hunting techniques

The method by which machairodonts hunted is hotly debated. It was originally thought 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 unlikely, 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 suggest 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 windpipe. 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 have), they could have subdued the animal before performing the killing bite.

[edit] Genera

The genera of Machairodontines^[4]:

Machairodontini

• Machairodus: Miocene; Eurasia, Africa and North America
• Homotherium: early Pliocene^[5] to latest Pleistocene; Eurasia, Africa and North America
• Xenosmilus: early Pleistocene; North America^[6]
• Lokontailurus: late Miocene; Africa^[1]
• Miomachairodus: middle Miocene; North Africa, Turkey
• Hemimachairodus: Pleistocene; Java

Smilodontini

• Paramachairodus^[7]: middle to late Miocene; Europe and Asia
• Megantereon: early Pliocene to middle Pleistocene; Europe, Asia, Africa, North America
• Smilodon: late Pliocene to latest Pleistocene, North and South America

[edit] Notes and References