Saber-toothed cat

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The fossilized skeleton of a sabre-toothed cat

The terms saber-toothed cat and saber-toothed tiger describes numerous cat-like species that lived during various parts of the Cenozoic and evolved their saber-toothed characteristics entirely independently. The saber-tooth morphology is an excellent example of convergent evolution as it occurred repeatedly and independently in at least four distinct mammalian groups.

1 Saber-tooth genera
2 Saber-tooth evolutionary tree
3 Why such large teeth?
4 Species
5 External links

[edit] Saber-tooth genera

The genera of sabre-toothed cats, along with the regions and time periods where they have been found, is summarized here:

Genus Name	Number of Species	Times	Regions
Smilodon	4	2.5 MYA to 11,000 YA	North America
Hoplophoneus	5	33.7 MYA to 23.8 MYA	North and South America
Dinictis	4	40 MYA	North America
Homotherium	10	3 MYA to 10,000 YA	Europe and Asia
Thylacosmilus (marsupial)	2	10 MYA to 1.8 MYA	South America
Metailurus	9	15 MYA to 8 MYA	China and Eastern Europe
Machairodus (Ancestral to Homotherium)	6	15 MYA to 2 MYA	Africa, Europe, Asia, and North America
Megantereon	2	3 MYA - 9,000 Years Ago	Africa, Eurasia, and North America
Dinofelis	6	5 MYA to 1.5 MYA	Africa, Eurasia, and North America
Paramachairodus	2	20-15 MYA to 9 MYA	Spain
Xenosmilus (1 specimen)	1	1 MYA (?)	Central Florida

[edit] Saber-tooth evolutionary tree

A statue of two saber-tooth tigers fighting

Saber-Tooth model display in the La Brea Tar Pits Museum.

All saber-tooth mammals lived between 9,000 and 33.7 million years ago, but the evolutionary lines that lead to the various saber-tooth genera started to diverge much earlier.

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.

Class Mammalia
- Subclass Marsupialia (diverged ? MYA, in the Cretaceous)
  - Order Sparassodonta (an extinct group of marsupial carnivores)
    - Family Borhyaenidae
    - Family Thylacosmilidae
      - Thylacosmilus
- Subclass Placentalia
  - Order Creodonta (diverged ? MYA, in the Paleocene)
    - Family Hyaenodontidae
      - Hyaenodon
      - Boualitomus
      - Laekitherium
      - Metapterodon
      - Triacodon
      - Parvagula
  - Order Carnivora
    - Family Nimravidae (diverged from the felioformes 48–55 MYA, in the late Eocene)
      - Dinictis
      - Hoplophoneus
    - Family Felidae (true cats)
      - Subfamily Machairodontinae (diverged ? MYA, in the ?)
        
        Tribe Homotheriini
        
        Homotherium
        
        Machairodus
        
        Xenosmilus
        
        Tribe Metailurini
        
        Dinofelis
        
        Metailurus
        
        Tribe Smilodontini
        
        Megantereon
        
        Paramachairodus
        
        Smilodon

[edit] Why such large teeth?

The most dramatic feature common to all of the saber-toothed cats was their enlarged upper canines. While it is generally agreed upon that they were used in hunting, the exact way they were used has been debated since the 1880s when Smilodon was first described.

[edit] Grabbing

Some paleontologists believe that the primary purpose is to grab and hold large prey. This is not well supported by evidence, however, as it has been shown that saber-teeth used in this way may be broken relatively easily, and fossil skulls with broken saber-teeth are rare.

[edit] Slashing

A more accepted hypothesis suggests that saber-teeth were used for a shearing bite to the throat or abdomen of large prey (Akersten, 1985), or to deliver deep stab wounds, from which the prey would eventually bleed to death. As the cat's teeth grew bigger, its prey such as Brontotheriidae may have adapted tougher skin, thus creating a feedback loop leading to bigger teeth on one side and tougher skin on the other (Cohen and Stewart, 2004).

There is a strong possibility judging from the position of molars designed for grasping and crunching bone that the sabretooth's bite was meant to come from the back of the neck. This way, the canines could puncture the esophagus while the back molars gripped/crushed the spinal column. This method of attacking prey's necks by leaping on their back is a hunting method common to most stalking cats today.

[edit] Display

Another possible use was as a social display structure (like most horns and antlers). If this is the case, it would support the theory that sabertooths were social animals.