Nature’s early “rehearsals” of the sabertooth: Rubidgea
Why is it that there are no sabertooths around today? Call it a matter of coincidence. Being a sabertooth is just one of the potential ways for a terrestrial predator to deal with the challenge of catching large prey and not getting killed in the attempt. The “sabertooth model” has evolved repeatedly in independent lineages of mammalian predators, but there have been a few times over the last 50 million years when there have been no sabertooths around, and (unluckily for us sabertooth enthusiasts) we now live in one such hiatus. But the potential to evolve the “sabertooth adaptations” is still around. Just look at your domestic cat sleeping in the sofa and consider that just a few key mutations would turn that tabby into a basic machairodont. First, make it bigger, maybe lynx size; second, introduce a key mutation to make the upper canines longer and laterally flattened; third, let the animal and its descendants play with their new weapons. Soon they will discover that the usual feline throat-bite becomes a devastating way to cause its prey to bleed to death in seconds, and from that moment on, a set of behavioural adjustments paves the road for the selection of morphological mutations that improve the efficiency of the sabertooth killing bite. And some fifteen million years later, you get something like Smilodon!
But what happened before there were cats, or any mammalian predators around? Well, nature did experiment with the sabertoothed predator model long before mammals or even dinosaurs appeared on Earth, but given the raw material then available, the result would have looked pretty alien for a human observer. Of course I am talking about the gorgonopsians, those synapsids (distant relatives of mammals) from the Permian period, which were the dominat predators of their time and looked like no creature walking this planet today.
Let us look at Rubidgea, one of the largest (brown bear sized) and latest gorgonopsians, which lived in South Africa some 250 million years ago. You would not call it a sabertooth, but it had many of the anatomical features that define those predators. The fearsome upper canines (1) were the primary killing weapon, while the protruding incisors (2) acted both to stabilize the bitten area (thus protecting the canines from some lateral strains) and to pull chunks of meat off the carcass when feeding. The complex shape of the cranio-mandibular joint (3) allowed the mandible to remain articulated with the skull even at gapes in excess of 90 degrees. Some ventral muscles of the neck (4) attaching in the base of the skull contributed to the downward motion neccesary to sink the canines into the flesh of prey. And once the gape was reduced through head depression, the jaw-closing musculature (5) acted to complete the bite.
Just as in mammalian sabertooths, the adaptations of Rubidgea allowed it to dispatch its prey quickly through massive blood loss, thus minimizing the time of struggle and the possibilities that the trashing prey would hurt the predator. Beyond that, the anatomical details were of course enormously different. But the story of the gorgonopsians shows us how some of the key adaptations of sabertooths are among the great, recurrent themes of the evolution of terrestrial predators.
Want to learn much more about the evolution of sabertooths? Get my latest book “Sabertooth”:
Wan to learn much more about how we bring those animals back to life through reconstruction? Get our documentary film “Bringing the Sabertooths Back to Life”:
Watch the trailer here: