Meet an early “extreme” sabertooth: Eusmilus sicarius

Sabertooth predators evolved at least 5 times independently among mammals. Among them, the first group to attain all the extreme adaptations that we associate with the sabertooth “model” were the nimravids, a family of true carnivorans that thrived in the Eocene and Oligocene periods. Almost 30 million years ago (when the ancestors of more familiar sabertooths like Smilodon were only ocelot-like creatures chasing smallish prey in the forests of the Old World), the nimravid  lineage of Eusmilus had already acquired all the “sabertooth” adaptations to the limit or nearly so. With the body size of a large leopard, the american species Eusmilus sicarius was a giant among the carnivores of its time. Of course it had enormous saber-like canines, but it also had other attributes that we see in other specialized sabertoothed predators: a huge downward projection on its chin; large incisors arranged in an arch well  ahead of the canines; an enormous mastoid process for the attachment of powerful neck muscles that aided the animal to sink its sabers into the flesh of prey; and quite a few other subtle features. Other families of mammals would make their own “experiments” with the sabertooth adaptations, but this nimravid was the first to achieve this level of sophistication. And yet the nimravids disappeared without descendance near the end of the Oligocene. The cause of that extinction is a great mistery, but certainly it is not a unique episode. Sabertooth predators have evolved time and again with enormous success, becoming the top predators in several continents, and each time they have been wiped off the face of the Earth. In a way, they died of success, something that should give us humans food for thought. But that is a different story…

And here is a life reconstruction of Eusmilus sicarius, the apex of sabertooth ev0lution in the Oligocene of North America. The animal was about the size of a large leopard. Some paleontologists think this species does not belong in the genus Eusmilus but rather in Hoplophoneus, but while we await for this matter to settle I will use the traditional name here.


Posted on 03/05/2013, in Uncategorized. Bookmark the permalink. Leave a comment.

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