Dueling Sabers: What This Marsupial has in Common With a Cat

Saber-toothed cats such as Smilodon are easy to recognize, thanks to their long, sharp canine teeth. But saber-toothed cats had an unexpected lookalike: something more closely related to a kangaroo than a cat.

Thylacosmilus was a saber-toothed mammal most closely related to marsupials, living in South America between seven and three million years ago. The marsupial’s young would continue developing after birth, while the placental saber-toothed cat gave birth to developed offspring.

No bigger than a modern jaguar, Thylacosmilus was small compared to Smilodon, but they both had very powerful necks, shoulders, and forelimbs. While a cat might sound fiercer than a marsupial any day, Thylacosmilus’ extra-long and pointy fangs were actually longer than the cat’s teeth, compared to body size. (But it’s unlikely the two ever met. Smilodon lived in North America as recently as 10 thousand years ago and only made it to South America after its marsupial doppelganger was extinct.)

The marsupial’s sword-like teeth went all the way back behind its eyes and were deeply anchored in bone. This reveals the stress these teeth had to endure during use. They came down past the animal’s lower jaw over a sheath-like structure that looks like a long chin, which may have protected the teeth. In fact, Thylacosmilus means “pouched saber” or “pouched carving knife.” Smilodon’s teeth were relatively shorter, beginning just in front of the eye. 

Other mammalian sabertooths include the family Nimravidae, sometimes called “false saber-toothed cats,” and the subfamily Machairodontinae (“dagger-like”), the earliest mammalian saber-toothed animals.  

Visit our Evolving Planet exhibition to see some of these saber-toothed mammals!