When is a tiger not a tiger?
A tiger is not a tiger when it is a saber toothed cat. The saber toothed cats represent a now extinct line, the Machairodontinae that diverged from the line that leads to the Panthera genus or modern big cats about 23 million years ago during the Miocene epoch. There are no descendents of the Machairodontinae line living today. The last of the breed, Smilodon fatalis and Smilodon populator are thought to have become extinct about 10000 years ago.
The big saber toothed cats are all thought to have descended from Megantereon, a true cat that enjoyed a wide distribution throughout Africa, Asia, North America and Europe over a period of about eight and one half million years during the late Miocene and into the Pleistocene. Megantereon had all the credentials. Its stocky jaguar sized body maxed out at about 350 pounds and this apex predator sported enlarged canines like his famous descendents. Megantereon's immensely strong forelegs were as large of those of a modern African lion.
Megantereon died out about 500,000 years ago, its remains have been found at some of the same sites as our ancestors Homo ergaster and Homo erectus, giving rise to speculation that the latter must at least occasionally have become prey.
Replacing and possibly evolving directly from Megantereon, Smilodon gracilis appeared about two and one half million years ago and became extinct about 500,000 years ago. Gracilis was actually a smaller animal than Megantereon, at most little more than 220 pounds, yet it was a true saber toothed cat and in all likelihood spawned the behemoth species which followed.
The big boys:
Gracilus gradually gave way to two larger species, Smilodon fatalis and Smilodon populator. Fatalis roamed North America and parts of South America. This species was approximately the size of a modern Siberian tiger, but the build was more powerful, almost bear like, and the fore body strength is unmatched by any of the predators of today. Smilodon fatalis may have reached a weight of 650 pounds, and may have stood almost 40 inches high at the shoulder.
Smilodon fatalis is thought to have fed on most of the larger game animals extant at the time and as it became extinct no earlier than 10,000 years ago it would have crossed paths with modern human beings. It is hard to visualize a positive outcome for the humans when such encounters occurred.
If Smilodon fatalis was awe inspiring, how much more so Smilodon populator, a true giant who roamed South America from approximately a million years ago to just under 10,000 years past. These titanic cats could weigh 900 pounds, measure over seven feet in length and stand four feet tall at the shoulder. Their famous fangs could top eleven inches in length.
Populator had immense front body strength compared to that of modern day big cats and even to its cousin, the remarkably powerful Smilodon fatalis. As the enormous canine teeth were not truly adapted for biting is thought that Smilodon used its strength to pull down and hold its prey, and then utilized its tremendously powerful neck muscles to power the fangs through the windpipe, blood vessels and nerves resulting in a relatively quick kill.
Smilodon would have needed all of this power to subdue animals like the horse, camel, bison, deer, young mammoths and mastodons and even the ground sloth and occasional human on which it apparently fed. The trade off for this robust body build was a decrease in speed, and Smilodon would probably have had difficulty in subduing smaller, fleet footed game.
It has been suggested, although it is not certain, that Smilodon behaved more like the social African lion and lived and hunted in prides or packs, rather than like the solitary tiger or leopard.
This lack of speed may have contributed to the downfall of Smilodon, which occurred only yesterday on the historic time line. Ten thousand years ago many of the larger game species also became extinct either due to the activities of upstart Homo sapiens or to clamatorial change consistent with the end of the ice age. In any event, Smilodon of all species were left without their best source of prey, the result was evidently catastrophic.
Many intact skeletons of both fatalis and populator are known, the former from the La Brea Tar Pits among other sites, and the latter from a number of cave sites in South America. Excellent reproductions may be found on line and in museums, and in various film specials on the History Channel, A and E and Discovery.