Science College, General Science Dept
4. Evolution of the Felidae
Here is a timeline of the Highlights of Felid Evolution:
As the Timeline shows, there was a primitive cat or cat-like animal as much as forty million years ago. It walked flat-footed rather than up on its toes and its brain was small, but, apart from these, *Dinictis* looked quite cat-like, with long canines and powerful jaws, short legs and a long tail. Some call *Proailurus* the first true cat, and some *Pseudailurus*. Wherever you draw the line, it's clear that evoution was slowly producing the complete cat.
Pseudailurus* is thought to be close to the ancestor of both the modern cats and the sabre-toothed cats. Sabre-toothed cats were further sub-divided into dirk-tooths and scimitar-tooths. Both were characterized by elongated upper canines, but their shape differed in the two sub-groups. *Homotherium*, a scimitar-toothed cat, and *Smilodon*, a dirk-toothed cat, were American genera that survived until the Ice Age ended 10, 000 years ago.
*Smilodon* means "Knife Tooth." It was the largest of the many kinds of sabre-toothed cats, a foot shorter than modern lions but much heavier. *Smilodon* was formerly known as the sabre-toothed tiger.
To allow the fangs to strike, the jaw could be opened to an amazing 120 degrees! Probably they used their fangs to cut and pierce their prey, large, thick-skinned herbivores such as mastodons (large hairy elephants) and bison. This is in contrast to modern big cats which kill by suffocation rather than slicing through windpipe or carotid artery. The fangs could also have been used for display in social interaction.
*Smilodon* must have ambushed their prey as they had bob-tails (long tails are needed for rapid changes of direction during a long chase). Since a lot of old and injured skeletons have been found of this animal, it is thought that *Smilodon* might have lived in groups and shared their kill, much like modern lions. Thus older and weaker members were able to survive.
*Smilodon* could roar like the modern big cats. We know this from the structure of one of its bones, called the hyoid. It is thought that *Smilodon* became extinct mostly because its large prey died out due to climate changes at the end of the last Ice Age.
Another cat that became extinct in North America at about the same time is the American lion *Panthera atrox*. Until very recently, lions were everywhere that there were no glaciers-- North and South America, all across Asia, down into India, Europe and the British Isles, the Middle East and all through Africa. The northernmost Old World lions were enormous, the cave lions, with the longer hair necessary to survive the Ice Age. They have only recently become extinct.
There is controversy as to where the very first Pantherines evolved-- the Old or the New World? It is understood they came from the *Lynx* lineage but their place of origin remains in doubt.
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