THYLACOSMILUS (“POUCHED KNIFE” (Marsupial Cat): Hidden Biases

An example of convergent evolution, Thylacosmilus of South America resembled Smilodon (Saber-toothed Cat) of North America.  The size of a modern Jaguar, He had a stout muscular body to stalk his prey.  Living during the Miocene epoch (eight million years ago (mya) to two mya), this marsupial carnivore was the top predator of South America until the coming of Smilodon.

            The most notable feature of Thylacosmilus was his two upper canines which looked like sabers.  Unlike Saber-toothed Cat, his teeth were firmly set in his jaw.  Growing continuously throughout his life, these special teeth wore down through use.  However Thylacosmilus had extensions of his lower jaw which protected these teeth much like scabbards protect swords.

            Thylacosmilus often preyed on animals larger than Himself.  Since He had heavily muscled shoulders and neck, Thylacosmilus would often pounce on his prey.  Then by holding his victim down, He would kill Them by stabbing downwards with his teeth.

            Although He resembled a Cat, Thylacosmilus was not one.  Moreover, He was not the marsupial equivalent of the placental Saber-toothed Cats.  Instead, Thylacosmilus was a member of the Sparassodonts, an ancient family of marsupial predators.

            When the two continents of the New World connected, the Great American Faunal Interchange occurred.  Smilodon went south to invade Thylacosmilus’ territory.  Because He was too specialized in his hunting, Thylacosmilus went extinct.  The more flexible Smilodon completely took over his territory.

            Thylacosmilus highlights our hidden biases.  We assume that because He looked like a Saber-toothed Cat, that Thylacosmilus was one.  Also because He was a close relative of the Marsupials, we assumed that He was doomed.  What we may not understand that during the Interchange, many unique Mammals of both continents went extinct.  Moreover the Opossum Family (Didelphis) who are Marsupials expanded their range from South America to North America, and is still successful today.

            We all have biases that we may not be aware of.  Through his aggressive manner, Thylacosmilus forces us to face them.  He is nothing what we thought He was.  By respecting Him, we can discover what an amazing world lies beyond our perceptions. Let Thylacosmilus challenge your beliefs.