Machairodontinae: The Sabre-toothed Cats

The sabre-toothed cats of the Machairodontinae family were a widespread and morphologically diverse group of felids that roamed the earth from the Miocene to the Late Pleistocene. For millions of years the sabre-toothed cats were the dominant felid family, successfully occupying North and South America, Eurasia and Africa (Christiansen 2012). The cats of the Machairodontinae family were rather large and physically robust but it was their craniomandibular morphology which has caught the attention of evolutionary biologists and palaeontologists alike. The two large maxillary canines which extend from the upper jaw classify the Machairodontinae cats such as Smilodon fatalis as scimitar-toothed cats  (See figure 1.) in comparison to the extant conical-toothed cats (Panthera tigris) and the dirk-toothed feliforms (Barbourofelis sp.). The canines are elongated , curved, slightly serrated and laterally flattened, with a jaw gape of approximately 100-130 degrees compared to the much shorter canines of the conical-toothed cats with maximum gapes of 65-80 degrees (Wilson 2012). Extremely well preserved fossils of the Smilodon genus have made it the most famous sabre-toothed cat, mainly because it possesses the longest teeth in the Felidae family (up to 30cm in length).


 

Figure 1.  The lateral view (A) and frontal view (B) of a model of the skull of Smilodon fatalis (Brown 2014). 

 
These large scimitar like teeth, along with the well developed muscles in the neck and forelimbs, enabled the sabre-toothed cats to kill large prey and inflict wounds that were deeper and wider. Instead of the powerful and suffocating grip of a conical-toothed cats jaws, sabre-toothed cats had a shearing bite, using their neck muscles to severely wound prey and increasing the chance of major vascular injury (Brown 2014). Due to this difference in killing methods it has been postulated that the Machairodontinae family also had comparatively weaker jaws. So it can be assumed that the Machairodontinae family developed these large canines due to an abundance of large animals during their existence. However, this trait made the sabre-toothed cats over-specialised and when animals began to shrink in size over time, cats such as Smilodon fatalis were unable to hunt smaller animals (Martin 1980). Evolutionary biologists believe this is why we do not see any scimitar-toothed cats today and why the conical-toothed cats are now the dominant felid. 
 
References:
  • Brown, JG 2014, 'Jaw Function in Smilodon fatalis : A Reevaluation of the Canine Shear-Bite and a Proposal for a New Forelimb-Powered Class 1 Lever Model', PLoS ONE, vol. 9, no. 10, viewed 26 March 2015, doi: 10.1371/journal.pone.0107456.
  • Wilson, T, Wilson, DE & Zimanske, JM 2012, 'Pneumothorax as a predatory goal for the sabertooth cat (Smilodon fatalis)', Open Journal of Animal Sciences, vol. 3, no. 1, pp. 42-45.
  • Martin, LD 1980, 'Functional Morphology and the Evolution of Cats', Transactions of the Nebraska Academy of Sciences, vol. 3, pp. 141-154.
  • Christiansen P, 2012, 'Phylogeny of the sabertoothed felids (Carnivora: Felidae:Machairodontinae)', Cladistics, vol. 29, no. 5, pp. 543-559.
 
 

Comments

  1. Unknown28 March 2015 at 17:45

    The sabre-tooth cats are quite fascinating creatures.
    I also quite like how you mentioned the barbourofelids, who are an interesting case of convergent evolution- they look sort of like sabre-tooth cats but are in fact not even part of the felid family.

    A question: you say a reduction in the numbers of large prey led to the decline of sabre-tooth cats, many other big cats also hunt primarily large prey, so how do they still thrive but not the sabre-tooths?

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    Replies
    1. Lili Usher-Chandler29 March 2015 at 16:30

      Although some large cats today can hunt large animals they can also hunt smaller animals just as efficiently. Lions for example can take down full grown buffalo but they tend to hunt the smallest, youngest and or weakest individuals. Whereas the sabre-toothed cats had prey much bigger than even a fully grown buffalo or wildebeest. Sabre-toothed cats were also very robust and less agile than modern big cats, they had strong forelimbs but I suspect could not climb very well or run as fast as the Pantherinae felids ie leopards.

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  2. Tasmin1 April 2015 at 23:40

    Very cool. You mentioned that they had weaker jaws. This seems counter-intuitive, given that they would probably require very large massetar muscle attachment just to open and close the mouth. If the jaws were so weak, did they rely then on increased neck strength to bite and subdue prey? I was also interested in felid dentition – why do cats have three pairs of incisors, whereas we only have two?

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    Replies
    1. Lili Usher-Chandler4 April 2015 at 02:13

      It is a bit unfair to say that the sabre-toothed cats had weak jaws, but comparatively they did have weaker jaws than modern cats because they relied on a different method of killing their prey ie their large canines did the job instead of need strong jaw muscles. But yes sabre-toothes need more muscle mass in their neck and in comparison, modern felids hardly use their neck muscles. This link to a journal article has some really interesting information on the subject http://www.pnas.org/content/104/41/16010.full
      Referring the incisors, I do not know why there is three pairs but it is a trait also held by the most primitive cats and modern cats have either kept that number of pairs because it is useful or there is no significant selection on the number of pairs. Sometimes cats are born with 11 incisors and they tend to lose the incisors first with old age. The incisors are used for extra grip when holding onto prey.

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