A new study has shed light on a bizarre prehistoric South American saber-toothed animal, which is distinctly different from other saber-tooth predators. Saber-toothed cats are iconic for being considered fierce prehistoric predators. There are currently almost a hundred known species, and they have various differences.
In particular, the marsupial Thylacosmilus atrox, with a size like a jaguar's, lived roughly five million years in the past in the area of present-day Argentina. This marsupial saber-toothed animal is usually presented as the perfect example of convergent evolution.
It had huge canines that grow continuously, which made people mistakenly think it was more vicious than other placental carnivores and saber-toothed predators. It seems, however, that this is not the case.
University of Bristol School of Earth Sciences professor Christine Janis led an international research team that studied the teeth and skull of the animal. They published their conclusions in the PeerJ journal.
Janis said that the impressive canines do not conform to the animal's anatomy. For one, it lacks incisors for getting the meat off a prey's bone. It also does not have fused lower jaws. She adds that the Thylacosmilus' canines also differs from other saber-tooth cats by being triangular instead of flat.
Co-author and associate professor Borja Figueirido of Spain's University of Málaga said that its skull looks superficially like any other saber-tooth mammal, but has many differing details.
University of Birmingham lecturer Stephan Lautenschlager, a contributing author to the study, says that Thylacosmilus had a bite that was weaker than that of the saber-toothed tiger Smilodon. He adds that Thylacosmilus' canines and skull were weaker for stabbing but stronger for the 'pull-back' motion, which suggests it used its canines to open carcasses instead of killing prey.
In addition, Thylacosmilus had small molars that didn't wear down on its sides, as the molars of meat-eaters do. Based on the dental study of Vanderbilt University assistant professor Larisa DeSantis, the molars did not wear flat from above, consistent with bone-crushing. Instead, she says the microwear on the tooth surface shows that it ate soft food. The tooth wear is similar to cheetahs', who eat fresh carcasses. She says the animal did not crush bone with its molars and could have specialized instead of soft, internal organs.
Janis also added that the animal had short legs and a stiff back. It also did not have retractable claws. Thus, it was not capable of pursuing, pouncing, and holding prey. It may have therefore been a specialized scavenger.
She says that the canines may have opened carcasses, and its big tongue may have been used to extract internal organs. This is similar to extant mammals who do not have incisors, such as anteaters and walruses. They also possess big tongues that have specialized functions in acquiring and eating their food.
Thylacosmilus' environment and ecosystem on Argentina's plains five million years in the past would have been very different from the modern ecosystems. It was a very different life, with large, flightless avian predators called the phorusrachids, which are known as "terror birds."
Figueirido says that present-day Africa has killer predatory mammals and big scavenger birds, such as the vultures. On the contrary, Argentina's environment five million years in the past may have had it oppositely, where the mammals were the scavengers, and the big birds were the apex predators.