Xenosmilus (Wikimedia Commons).


Xenosmilus (Greek for "foreign sabre"); pronounced ZEE-no-SMILE-us


Plains of southeast North America

Historical Epoch:

Pleistocene (one million years ago)

Size and Weight:

About five feet long and 400-500 pounds



Distinguishing Characteristics:

Large size; muscular legs; relatively short canines

About Xenosmilus

The body plan of Xenosmilus doesn't conform to previously known saber-tooth-cat standards: this Pleistocene predator possessed both short, muscular legs and relatively short, blunt canines, a combination that has never before been identified in this breed--though paleontologists do believe Xenosmilus was a "machairodont" cat, and thus a descendant of the much earlier Machairodus. (The unique skull and tooth structure of Xenosmilus has inspired a peculiar nickname, the Cookie-Cutter Cat.) It's as yet unknown whether Xenosmilus was restricted to southeast North America, or was more widely distributed across the continent (or, for that matter, ever made it down as far as South America), since the only two fossil specimens were unearthed in Florida in the early 1980's.

The most striking thing about Xenosmilus, besides its cookie-cutter bite, is how big it was--at 400 to 500 pounds, it was just shy of the weight class of the largest known prehistoric cat, Smilodon, better known as the Saber-Toothed Tiger. Like Smilodon, Xenosmilus clearly wasn't suited to stalking or pursuing prey at high speeds; rather, this cat would have lounged in the low branches of trees, pounced on slow-witted megafauna mammals as they passed by, dug its cookie-cutter teeth into their bellies or sides, and then let go and leisurely followed them as they slowly (or not-so-slowly) bled to death. (The bones of peccaries, a type of pig native to North America, have been found in association with Xenosmilus fossils, so we at least know that pork was on the menu!)