Saber-toothed tiger.

Saber-toothed tiger was slightly shorter, but much heavier compared with a modern lion. It was able to reach 79 to 98 inches in length and 150 to 661 pounds of weight. Despite its name, saber-toothed tiger was not a true tiger. This prehistoric animal is only distantly related to modern lions, cheetahs and tigers.

What is a Saber Tooth Tiger
In short, Saber Tooth Tiger is prehistoric carnivorous mammal, with distinctive pair of long razor sharp canine teeth, that got extinct at the end of the Ice Age some 10,000 years ago.
It is very popular among the prehistoric animals due to its fascinating looks and its elongated sword shaped canine teeth.
It was found in North and South America.
It existed between the Eocene and the Pleistocene period which ranges from 55 million years to 10,000 years ago.
It was the primary predator in the woodlands and grasslands.
Previous studies of fossils suggests that it became extinct mainly due to lack of food which was caused by the climate change. Climate change caused plants extinction which resulted in extinction of herbivores (animals that eat plants) and ultimately it caused Saber Tooth Tiger extinction as there were no more herbivores to hunt for food.
Recent studies on fossils deny the above reason of extinction but do not provide any new theory on saber tooth tiger extinction.
The Saber Tooth Tiger is also called the saber-toothed lion or saber toothed cats but in reality it is not a tiger or a lion or even close to the cats that we have today. It belongs to an extinct sub-family of the cat family (Felidae) which is called Nimravidae or the subfamily Machairodontinae.