Saber-toothed lions and tigers no doubt struck terror into our ice age ancestors, but what to make of a saber-toothed squirrel? Humanity never had to decide if the newly discovered species Pseudotherium argentinus was frightening or cute since it lived during the Late Triassic, when even the dinosaurs were yet to peak, but some Hollywood animators may be feeling smug about their capacity to beat paleontologists to the truth.
Pseudotherium was discovered by Dr Ricardo Martinez of Argentina’s University of San Juan based on a 6.9-centimeter (2.8-inch) adult skull that suggests the whole creature was 25 centimeters (10 inches) long. It wasn’t a squirrel, or even technically a mammal, instead being classified as a mammaliamorph – a group of close mammal relatives – living 231 million years ago. Pseudotherium may have been quite closely related to an ancestor of mammals, but it lacked the distinct expanded brain regions that separate mammals from our predecessors, according to the study in PLOS One.
Nevertheless, Pseudotherium shows a remarkable resemblance to Scrat, the squirrel/rat ancestral creature that is one of the stars of the Ice Age cartoons. "The new species has a very long, flat, and shallow snout, and its very long fangs located almost at the tip of the snout, so the resemblance [to Scrat] is tremendous," Martinez told Argentina’s Agency CTyS-UNLaM. He even considered naming the species after the character.
Pseudotherium isn’t the first creature we have discovered that looks like this. Cronopio dentiacutus was a true mammal with a similar size and shape to Pseudotherium that lived 95 million years ago during the Cretaceous and whose 2011 discovery also followed, rather than inspired, the films. The resemblance is a result of convergent evolution, where similar environmental conditions produce parallel solutions. We can only speculate on where their common resemblance to a cartoon character comes from.
With only one specimen, we don’t know much about Pseudotherium’s lifestyle or why it needed such fearsome teeth. Living before the first flowering plants, they would certainly not have been to open acorns. Instead, it probably had a diet of insects or smaller animals. The teeth could have been used to catch and tear into prey but may also have been for fighting over territory or mates, particularly if the specimen Martinez found was male.
The discovery was made in the multi-colored rocks of Ischigualasto, San Juan, northwestern Argentina, a location known as Moon Valley and a rich source of Triassic fossils. More recently, these include two new species Martinez found near the Pseudotherium skull, one among the oldest relatives of the famous long-necked sauropods and the other a member of the rare lagerpetid small dinosaur relatives.