Homotherium from South America?

According to a news report released last night the first confirmed remains of a scimitar-toothed cat have been found in Venezula, a contemporary of the dirk-toothed cat Smilodon. The uncovered remains are said to represent six individual sabercats, called Homotherium, including a complete skull. This makes Homotherium one of the most widely traveled and persistent of all sabercats; it has been found in Africa, Europe, Asia, North America, and South America, and the genus was present from about five million years ago to 10,000 years ago (although it became extinct in different parts of the world at different times).

The article announcing the discovery leaves a few things unclear, however. The term "saber-toothed tiger" has been out of favor as a common term for at least fifty years (see G.G. Simpson's discussion of the subject in The Meaning of Evolution). There were several groups of saber-toothed predators in the past but not all of them were true cats (despite appearances), and creatures like Smilodon and Homotherium belonged to a group of true cats called the machairodonts. This group is distinct from living big cats in a number of ways and are not more closely related to tigers than living big cats as a group are related to each other (for all their diversity most fall into one genus, Panthera). Today the machairodonts are commonly called "saber-toothed cats," although I usually prefer the shorter derivation "sabercat" when writing.

So what do terms like "scimitar-toothed" and "dirk-toothed" mean? Even though they looked similar sabercats were not all alike in form or habit, and at present it seems that there were at least three different groupings of sabercats that employed different hunting and killing techniques. Scimitar-toothed cats, like Homotherium, had shorter and more roughly-serrated canine teeth and relatively long legs, while dirk-toothed cats like Smilodon had very long and finely-serrated canines but a bulkier build. The somewhat strange sabercat Xenosmilus, alone in the third group, had a smattering of features from both including a heavy build and short, broad teeth. Generally it has been inferred that these traits denote different prey preferences and hunting styles, dirk-toothed cats going after prey much larger than themselves while the scimitar-toohed cats fed on smaller, quicker animals. Although there is still debate over how sabercats caught and killed their prey these ecomorphological differences suggest that the role of sabercats in ancient habitats was not equivalent to those of their modern-day felid cousins.

As far as I am aware the Homotherium fossils have only just been discovered, which means we'll have to wait a little while before finding out more details in the technical literature. Still, it's interesting news that hopefully will give the often-overlooked Homotherium some time in the spotlight.