Some believe that the Saber-Toothed Cats, impressive prehistoric big cats disappeared long ago, went extinct because the evolution of their canines too such length that they no longer could hunt, bite and eat. It’s really wrong; The animal had an astonishing capacity to crack his mouth wide-open, giving it a strong hook to catch a prey, as you can see in the following animation which allows a comparison with the modern lion anatomy:
All the details on Saber-Toothed Cats anatomy are on HowStuffWorks.