What is NOT a cat?

In the past many people, maybe even yourself, have mistaken prehistoric or living organisms as 'true cats' that are in fact very different to felids, genetically and morphologically. These false cats are the result of convergent evolution and did not evolve from Proailurus. But the prehistoric mammals mentioned here were obligate carnivores, typically only hunting live prey and so they developed similar attributes to capture and kill animals. As previously mentioned felids appeared quite recently on the evolutionary time scale, while the first sabre-toothed mammals resembling cats appeared approximately 50 mya, long before the Felidae family emerged (van den Hoek Ostendel et.al 2006). The Machaeroidinae family included the very first sabre-toothed cat-like organism. Around 44mya the Nimravids appeared followed by the Barbourofelids (23mya) the name itself contains the misleading suffix 'felid'. At first the Barbourofelids were considered a subfamily of Nimravidae but it was later decided that the Nimravids are more canidlike while the Barbourofelids were more felid-like. However, based on dental morphology and skull shape they would also have to be placed in a separate family from the true sabre-toothed cats (Machairodontinae) and felids (See figure 1) (van den Hoek Ostendel et.al 2006).


 Figure 1. Sketches of Barbourofelis fricki (left) & Machairodus coloradensis (right) (Martin 1980).

 

 

One other notable false sabre-toothed cat is Thylacosmilus, a metatherian sparassodont from South America (c. 7 mya), more closely related to modern marsupials with large canines that originated from the top of the skull extending downwards through the upper jaw. The nimravids and barbourofelids are both placed in the suborder Feliformia, which also contains modern cat-like mammals including the viverrids and hyaenids. They all share one important common attribute which is a double chambered auditory bullae, crucial in identifying feliforms (Ewer 1973). Although many would not consider a hyena a cat, it is easy to mistake a viverrid for a cat. The most common viverrids are civets, genets and mongooses. Both arboreal viverrids and felids are very phylogenetically similar and have fully retractile claws. Yet the largest difference between the two is that viverrids are usually omnivorous and use their retractile claws as an important tool for movement, while strictly carnivorous felids retained their retractile claws primarily for hunting (Gonyea & Ashworth 1975).


References:
  • Ewer RF 1973, The Carnivores, Cornell University Press. 
  • Gonyea W & Ashworth R 1975, 'The Form and Function of Retractile Claws in the Felidae and Other Representative Carnivorans', Journal of Morphology, vol. 145, no. 2, pp. 229-238.
  • Martin LD 1980, 'Functional Morphology and the Evolution of Cats', Transactions of the Nebraska Academy of Sciences and Affiliated Societies, vol. 8, pp. 141-154.
  • Van den Hoek Ostendel LW, Morlo, M & Nagel D 2006,'Fossils explained 52', Geology Today, vol. 22, no. 4, pp. 150-157.

Comments

  1. Unknown25 April 2015 at 17:33

    Non-felid sabre tooths are quite fascinating creatures. Predatory mammals seem to have a bit of a tendency to develop sabre teeth (indeed predatory therapsids in general, as the non-mammalian gorgonopsids also had what we could call sabre teeth).

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    Replies
    1. Lili Usher-Chandler25 April 2015 at 20:11

      Correct. I do enjoy studying the evolution of supercarnivorous animals, but mammals especially. These large maxillary canines (for mammals at least) are used to cause serious damage as a way to kill prey, in comparison to for example lion jaws which are used to hold and suffocate prey or break their neck.

      Delete
  2. Tasmin2 May 2015 at 22:21

    I find this very interesting, that these animals were evolutionarily older. What is so fantastic about the auditory bullae? Why is it crucial for identifying feliforms?

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    Replies
    1. Lili Usher-Chandler6 May 2015 at 01:52

      I apologise, but I should have and have now said in the blog above, that feliforms are identified specifically by a double chambered auditory bulla. It is composed of two bones joined by a septum. Briefly put, carnivores specifically have enlarged auditory bullae that can translate certain vibrations of the eardrum into signals their brain interprets as sound. Thus felids and other carnivores usually have high sensitivity to particular frequencies, so they can hear things humans usually can't such as the slight rustling of leaves when there is prey nearby. There is not enough current research that has been conducted to study the function of the septum and double chambered structure in feliforms, unfortunately.

      Delete

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